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- FUEL MANAGEMENT AND SAFETY
- Accurate and efficient fuel management on the part of the airline and
flight crews improves safety, because it requires additional attention,
accuracy and increased situational awareness. By accurately managing
fuel, airlines can:
- Ensure that proper risk management processes for fuel boarding are in
place by carrying enough fuel to the high-risk airports and less fuel
to airports where it is not required.
- Minimize the risk of unplanned fuel diversions
- Ensure that flights land with adequate fuel on board
- Ensure that crews maintain a safe and efficient approach to fuel
management
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- FUEL MANAGEMENT AND THE ENVIRONMENT
- A 1% saving in fuel for a B737-300 aircraft will result in a yearly
reduction of fuel consumption by 100 metric tons (32,835 US Gal) and
save airlines approximately USD$50,000 per aircraft. It will also
decrease the emission of pollutants by the following amounts:
- 318.7 tons of CO2; 123.9 tons of H2O; 2.112 tons of NOx; 98 kg of SO2;
and 56 kg of CO
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- ECONOMIC IMPACT OF EFFICIENT FUEL MANAGEMENT
- Fuel is the second largest cost item after employee wages. For some
airlines, fuel represents approximately 20% or more of the total budget.
Airlines that have an aggressive fuel saving program can reduce their
overall fuel budget by at least 5%.
Fuel savings directly affect the bottom line. In an environment
of extreme competition, airlines that manage fuel efficiently will have
a definite competitive advantage.
Because of low profit margins, to compensate for each dollar
wasted in fuel burn, airlines would have to generate 15 to 20 dollars in
additional revenues to achieve the same profit. All departments
including Flight Operations must be accountable for efficient fuel
management.
- Effective communications, efficient procedures, adequate training
programs and proactive management of each flight will minimize overall
corporate costs (fuel, time cost, connections, etc) and ensure the
company’s success. For example,
by slowing down flights scheduled to arrive early not only saves fuel,
but also reduces emissions and, in some cases, prevents ramp and gate
congestion. On-time arrivals improve ground staff efficiency and
customer service.
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- Airlines must sensitize government regulators to the additional costs
such as delays, fuel and emissions, which result from certain
regulations, inefficient ATC route structure and excessive ATC
restrictions. Some of the factors that contribute to an increase in fuel
consumption and gas emissions include insufficient ATC staffing,
inadequate and antiquated equipment, inefficient and cumbersome
procedures, unnecessary route or altitude restrictions for controllers’
convenience, restrictive and inflexible noise abatement procedures, and
poor communication facilities.
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- BASIC FACTS REGARDING FUEL CONSUMPTION
- Airlines perform limited maintenance to their fleet due to the cost of
aircraft down time or spare engines.
Regular maintenance contributes to an airplane’s fuel
efficiency. During normal line
operation, for every 3,000 hours of flight time or 1,000 cycles, new
airplanes will lose approximately 1% efficiency. After a few years of
operation, the fuel burn performance of an aircraft will tend to
stabilize at between 5 - 7% above baseline new aircraft performance
levels. Some aircraft will burn
as much as 10% or more in certain circumstances.
- Major engine overhauls will normally recover approximately ½ of the
efficiency degradation compared to a new engine. Engine wash, airframe
control rigging, buffing and good paint condition can reduce fuel burn
from one to two percent in some cases.
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- EFFICIENT FLIGHT PLANNING
- An efficient flight planning system should have the full range of Cost
Index (CI) planning capability with appropriate vertical and lateral
optimization. The vertical and lateral profiles should change with the
planned CI because the winds and temperatures vary at different
altitudes. Consequently, the final flight levels and route solution
would normally differ. For greater accuracy, a flight-planned route
should include the planned takeoff runway, the departure and arrival
procedures, and landing runway rather than planning from centers of the
departure and destination airport.
- In addition, Cost Index based flight plans should be available for
non-Flight Management Computer Systems (FMCS) equipped aircraft. CI
optimization is a critical tool for performance optimization and cost
control. While many modern larger aircraft are equipped with CI
optimization embedded in the FMCS, many regional jet aircraft and other
older generation aircraft, do not have the necessary technology.
However, CI optimization is available for these aircraft from vendors of
Cost Index systems, which operate independently of the FMCS. That
technology is available as a software application on Class 1 and Class 2
Electronic Flight Bag (EFB) systems and even as a flip chart or
booklet-based system. Compared to fixed-Mach flight planning or Long
Range Cruise (LRC) speeds, CI optimization of planned speeds will yield
savings from 2 to 3% and in some cases as much as 10% when a flight is
restricted to a low altitude or in unusually strong winds.
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- In certain circumstances, on-board CI performance systems, whether
embedded in the FMCS or operating on an EFB or in a flip chart, will be
of great value for making tactical decisions by flight crews and assist
in saving fuel and valuable time, or both.
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- STATISTICAL AND DISCRETIONARY FUEL
- One of the difficult tasks for flight dispatchers and pilots during
flight planning is to board the correct amount of fuel above the minimum
regulatory requirements. Because of the high cost of carrying extra
fuel, careful consideration is required to minimize expenses.
- It is therefore important to develop and maintain up-to-date statistics
by aircraft type (from a Fuel Management Information System) on the
amount of fuel consumed above the planned fuel burn for each route and
aircraft type. Several factors will impact a flight’s fuel burn,
including the time of day, day of the week, seasons, runway
configuration, training, etc.
- The idea is to acquire data from which discretionary fuel can be better
optimized on a specific route. Used in conjunction with other
information such as Airport Traffic Demand charts and graphical traffic
display, traffic advisories from ATC units, and weather information,
fuel can be optimized accurately resulting in minimum cost and improved
safety, because it will also decrease the chances of unplanned
diversions.
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- Experience has demonstrated that without proper statistics, an average
of 2 to 3 times the amount of discretionary fuel was carried compared to
the amount determined from statistical information. A confidence factor covering 99% of
the flights will demonstrate that in most cases, no additional fuel
above regulated contingency fuel is required. Flight statistics help increase the
flight crew’s confidence level of the flight planning system and will
reduce their tendency of ad hoc fuel boarding.
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- ALTERNATE SELECTION
- One of the most important aspects of fuel optimization is the alternate
selection process. With today’s modern aircraft and advanced approach
aids at modern airports, diversions are a rare event. The weather
requirements for an alternate are very conservative and have not changed
in recent years in spite of the significant advances in aircraft
navigation and landing systems, improved weather reporting including
satellite and radar imaging and improved airport ground systems
technology. The primary reasons for diversions are equally divided
between medical emergencies, maintenance or weather. Most diversions are
not to the planned alternate.
- There are several reasons why the selection of alternate airports is not
fully optimized. Many airlines have not carefully analyzed the best and
most efficient alternate for each destination. Many alternate airports are selected
because of a dispatcher’s familiarity with that airport or with the
services available in case of diversion, or for personal preferences,
etc. Many times a long alternate is selected with the full knowledge
that if a flight diverts, it will divert to an airport other than the
designated alternate airport.
- As for pilots, they might prefer a specific alternate because of
comfort, familiarity, available charts, perceived traffic, ground
servicing and communications after landing, etc.
- When an alternate is carried for regulatory reason such as international
flights but the weather and traffic at destination are such that a
diversion is very unlikely, the closest suitable alternate (the one that
requires the least fuel) should be selected. In some cases, the use of
re-dispatch or re-clearance can be used where the alternate can be
dropped once the flight is approaching its destination.
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- On longer-range flights, not only is it expensive to carry a long
alternate [from a fuel point of view], but payload can also be affected.
Every ton of fuel not carried to destination can enable the boarding of
additional 10 revenue passengers.
- As the risk of diversion increases, an important factor to consider when
selecting the alternate is customer service and rerouting. Look for an alternate that will offer
a quick a turn-around and a rapid return to normal operation, proximity
to hotels and restaurants, customs and visa requirements, etc.
- Airlines should, subject to regulations, establish a clear policy that
outlines the actions to take by the crew when the weather at destination
or alternate airports deteriorates.
The following scenarios could be considered:
- If the weather at destination is above alternate weather limits and the
weather at the designated alternate airport decreases unexpectedly
below normal approach limits, the flight can continue at the captain’s
discretion after verifying that the landing at destination can be
assured and the no unreasonable traffic delays are expected.
- If the weather at destination is between normal approach and alternate
weather limits, the weather at the alternate should remain at least
above normal approach limits with no traffic delays expected.
- If the weather at destination decreases below normal CAT I ILS approach
limits, then the weather at the designated alternate should remain
above normal alternate limits.
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- Caution is required to ensure that a flight does not end up without
options. Unless the landing can be safely assured at either the
destination or the alternate airports with no anticipated ATC delays, an
enroute landing should be considered.
- To improve the alternate selection process, consider the following
steps:
- Designate a primary alternate at every destination
- Perform a detailed review of all
possible alternates for each new destination
- List all the available alternates in order of fuel requirements for
reference
- Ensure that the information regarding handling details, communications,
approach charts, etc are readily available for the closest alternates
- Ascertain that both the crews and dispatchers are fully familiar the
primary and closest alternates for each destinations
- Perform regular reviews to ensure adherence to the established
alternate selection process by both pilots and dispatchers.
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- RE-DISPATCH AND RE-CLEARANCE TECHNIQUES
- Re-Dispatch and Re-Clearance procedures offer significant potential
savings. However, the Re-Dispatch
technique is preferable because ATC clears the flight to destination
from the onset and all the necessary fuel requirements are clearly
established before flight departure.
Re-Clearance, on the other hand, requires the flight to change
destination while enroute, which is cumbersome. With accurate flight
planning systems, most of the flight planned contingency fuels remain
unused and the re-dispatched technique will bring large benefits in both
fuel savings and payload optimization especially on long-range flights.
Depending on an airline’s fuel policy, between 5 - 10% of contingency
fuel is normally boarded. Since
flight conditions can vary during flight and possibly the alternate
airport is no longer required for arrival, re-dispatching the flight can
prevent an enroute stop while carrying maximum payload.
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- FUEL TANKERING
- Fuel tankering should be an integral part of the flight planning system.
For ecological reasons, consider tankering only when there is a definite
commercial benefit for the airline. Tankering is normally limited to
short flights or for tactical reasons. Consider the full cost of
carrying the additional fuel, including wear and tear on the aircraft.
To avoid overweight landings, the planned landing weights must be
monitored. Anticipate the possibility of last minute additional cargo,
go-show passengers or changes in aircraft route scheduling. Also
consider the departure and arrival runway conditions, the lower enroute
altitudes that, in some cases, can limit the cruise altitude options to
avoid turbulence or cause additional detouring around weather.
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- WEIGHT MANAGEMENT
- Carrying extra weight on board will result in additional fuel burn
equivalent to about 4% per hour of the extra weight carried. This will
vary depending on the aircraft type, the flight profile flown, etc. The best way to get an accurate
measurement of the penalty associated with the additional weight carried
is to compute the flight plan for different weight combinations.
- Here is a list of items which will result in significant additional fuel
consumption when all added up.
- Old magazines and newspapers
- Galley containers, ovens, extra supplies
- Excess duty free material
- Extra water in the tanks not required for the flight
- Pillows and blankets
- Excessive crew baggage
- Extra airline magazines and publicity in seat pockets
- Infrequent toilet servicing
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- Empty baggage and cargo containers
- Moisture accumulation in the aircraft insulation
- Accumulated dirt every where in the aircraft
- Parts of the aircraft which can be replaced by lighter ones such as
carpets, seats, fire extinguishers, tires, etc.
- Fuel tankering
- Over fueling
- Aircraft servicing, caterers, In-Flight service and line maintenance
personnel all have an important role to play to minimized excess weight
on board aircraft.
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- CENTER OF GRAVITY MANAGEMENT
- An aircraft stability in flight is assured by maintaining the Center of
Gravity forward of the Center of Lift. To do so will require that the
tail plane produces downward lift which has to be compensated by the
main wings. The further forward the Center of Gravity, the greater the
downward lift required from the tail plane and the more the main wings
have to compensate and therefore the greater the drag. There are obviously limits to the fore
and aft loading of an airplane to retain a minimum stability in flight.
- Depending on the aircraft type, drag created by loading an aircraft to
the maximum forward Center of Gravity can increase drag by up to 3%
compared to loading the aircraft to the most rearward Center of Gravity
where drag can be reduced by approximately 1.5% of nominal drag. Therefore properly managing the Center
of Gravity can have a significant impact on fuel efficiency.
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- FLIGHT MANAGEMENT SYSTEM PROGRAMMING
- Most modern aircraft are equipped with different sophistication types of
Flight Management Systems (FMS).
Some will have fuel Cost Index [CI] optimization capabilities and
extremely accurate time and fuel predictions. Others will have basic
capabilities with no speed or CI optimization. Whatever system is
available, crews should make maximum use of the FMS capabilities to
monitor the operation and operate the flight as efficiently as possible.
Like any computer, the quality of the information entered in the FMS
will determine the accuracy of the system’s information and predictions.
- The present discussion will center on the more advanced FMS in an
attempt to make the best use of their capabilities from a crew point of
view.
- At the preflight programming level, the FMS will serve as an excellent
means of performing a cross check of the flight plan time and fuel
data. While many pilots have
different methods of performing fuel checks during flight planning, many
limitations exist. Fuel performance charts will only consider data
provided by manufacturers and they have many limitations. Items such as
aircraft specific airframe and engine in service deterioration, Cost
Index, winds and temperatures at specific waypoints, last minute Zero
Fuel Weight changes, etc. are not considered. Some crews will use an average burn
figure per hour and will do a rough check based on the flight time, etc.
The problem is that all the various methods are very approximate and
basically are not precise methods of cross checking the accuracy of the
flight plan.
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- Accurate programming of the FMS for long-range flights is critical. For instance, a one-degree deviation
in temperature will change the true airspeed by one knot. While that may
not seem significant consider the following example. If the average temperature is 10
degrees above or below standard, on a 15 hour flight, it can cover a
distance of ± 150 nautical miles and impact the Estimated Arrival Time
by as much as ± 20 minutes.
- Insert the most accurate available information in the FMS. For instance, the departure runway,
Standard Instrument Departure with appropriate transition, the planned
route with the planned arrival procedure (STAR or FMS) and the planned
runway should be inserted during preflight. It is critical to enter the winds and
temperatures at each waypoint (ideally these should be downloaded
directly from the flight planning system) as well as the altitude
step-climbs (or descents) as these will be used by the FMS to further
compute additional wind predictions and times. If the FMS optimum
altitude predictions are to be used, the winds above and below the
planned cruise flight level must also be inserted, as these will be
considered when determining if an altitude change is fuel-efficient. The
more advanced FMS will also consider the Cost Index selected to
determine the optimum altitude.
- Once all of the available information has been inserted, the fuel and
flight times should be accurate and any discrepancies should be
reconciled before flight. The minimum Fuel over Destination (FOD), which
should include the regulatory final holding fuel (30 or 45 minutes),
plus the alternate fuel, should be subtracted from the planned FOD to
determine the amount of discretionary fuel for the trip.
- Improperly programming the FMS may lead to crews wanting to add fuel to
compensate for inaccuracies. This
can be costly especially on long-range flights where it can impact the
payload.
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- The in-service performance deterioration factor (drag factor) of a
specific aircraft should be entered in the FMS for increased accuracy.
- On long flights, after several hours, more recent winds and temperatures
should be updated. When the
cruise altitude is different from flight plan, winds and temperatures
for the new altitudes should be inserted.
- Once airborne, the FOD and ETA should be monitored continuously and
cross-checked with the flight plan. Any differences should be
reconciled. If a high Cost Index
was planned for the flight and the FOD falls below the desired level,
the CI should be reduced to ensure that adequate fuel is available on
arrival. If the flight is held at
a less than optimal altitude for some time, allow the FMS to compute the
best Mach for that altitude to minimize the fuel burn.
- If the ETA varies from the normally scheduled arrival time, coordinate
with Operations Control and Dispatch to adjust the ETA as discussed in
the Mission Management section.
- The idea is to ensure that the most accurate information is inserted in
the FMS to maximize it usefulness, improve safety while reducing cost.
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- AUXILIARY POWER UNIT (APU) MANAGEMENT
- While always keeping the comfort passengers in mind, efficient APU
management can yield significant savings. Depending on the aircraft type, the
cost of APU usage is about 30 to 50 times more expensive than the gate
supplied electrical power. Not only does the APU consume a large amount
of fuel and cause pollution, it also incurs high maintenance cost.
- The APU is often used to compensate for shortcomings in ground
operation. Here is a list of
reasons that lead to excessive use of APU:
- Inadequate SOPs;
- Ground electrical power unavailable;
- Ground air conditioning or heating unavailable;
- Shortage of ground personnel to connect the ground support equipment;
- APU air conditioning provided to unattended airplanes;
- Aircraft abandoned with the APU running;
- APU operating overnight;
- Excessive aircraft towing using the APU;
- Aircraft plugged to ground electrical but APU still operating;
- Maintenance performed on the aircraft with the APU instead of ground
power;
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- Excessive charges for ground equipment or lack of an adequate servicing
contract with ground handling agencies often encourages airlines to use
the APU;
- Incompatible or unreliable gate power for certain aircraft types;
- Crews who have completed their flight leave the aircraft with the APU operating;
- Unnecessary operation of APU during taxi, takeoff and landing;
- APU operating in flight with unserviceable generator; and
- Lack of training and sensitization of personnel.
- When the APU is required, the load should be minimized by using
pneumatics only when necessary. For certain APU types, the fuel
consumption is reduced by as much as 35%.
- If the APU is started when a flight arrives, and if the turn time for
the airplane is more than one hour and is left unattended, consider
de-powering the aircraft once the passengers have deplaned.
- Airlines should develop a system to track APU usage and correct any
excessive usage.
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- ENGINE START-UP AND TAXI
- Avoid starting engines at the gate because it will not only increase
fuel consumption and pollution but it can also be hazardous for ground
personnel. If a departure slot
time would result in a long taxi time and if gate occupancy permits,
consider delaying the pushback and absorbing some of the delay at the
gate with the engine off.
- To minimize departure delays and ramp congestion, engine start-up and
push-back procedures should be streamlined and coordinated. Inefficient
procedures at busy airports can delay several other aircraft with
engines operating. Once a ramp
crew has pushed back an airplane, the ramp crew must disconnect the tow
bar and communication cord as soon as possible. To minimize power requirements during
initial roll out and minimize ground hazard, position the aircraft in
the initial taxi out direction. An engine-out taxi procedure should be
considered when:
- Ramp and taxiway conditions permit
- The aircraft weight is below maximum landing weight
- The anticipated taxi time and specific aircraft system permits.
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- If a flight’s weight is light, and the flight crew chooses to taxi with
all engines running, the crew may have to ride the brakes. This can cause excessive wear and
heating of the brakes. Cold soaked engines might require longer warm up
time.
- Engine out taxi requires slightly more anticipation compared to taxiing
with all engines operating. Crews
that never use engine out taxi procedures will consider them awkward
while crews who consistently use them will consider them routine. Before
using engine out procedures, airlines must ensure that the SOPs
regarding engine out taxi are well established and crews properly
trained. When unanticipated
delays are encountered during taxi-out, consider engine out taxi or
shutting down engines during extensive delays.
- On some engine types, the use of engine anti-ice on the ground will
result in increased idle RPM and fuel consumption in addition to the
possibility of foreign object damage. On slippery taxiways, it might be
difficult to stop the aircraft with engines spooled up. Momentarily
turning off engine anti-ice will facilitate stopping. In congested ramp areas, delay turning
on engine anti-ice to prevent blasting due to spool up. If de-icing is to be performed at a
centralized de-icing area and a long deicing is anticipated, consider to
shutting engines down during de-icing.
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- Taxi speeds
- A lot of time can be made up or lost while taxiing. In ideal conditions, the recommended
taxi speeds should be around 10 knots for maneuvering and on straight
taxiways; however, speeds up to 30 knots are acceptable. Flight crews
must remember that fuel burn with engines that are idling on the ground
equates approximately 25% of cruise power.
- Choice of Departure Runway vs. Taxi times
- At low-density airports, there might be a choice of departure
runways. It is always difficult
to establish a trade off point regarding the cost of taxiing versus
air-time but here is a rule of thumb. Strictly based on fuel
consumption, it might be worthwhile to taxi 4 minutes for every minute
of air-time saved. For example, a flight departing in a direction 180
degrees from the intended flight course may need to travel an extra 15
miles in the air. This will have to be made up at cruise altitude at the
cost of 2 minutes of air-time. In
this case, it may be more cost efficient to taxi an extra 6 to 8
minutes. There are other
considerations however; if a flight is late with several connections and
a short turn around on arrival and if the selection of a different
runway can possibly result in additional ground delays, it might be
worthwhile to use the most expeditious runway. Crew cost is another factor to
consider.
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- REDUCED THRUST TAKE-OFF
- Compared to full thrust, the use of reduced thrust will not reduce fuel
consumption during takeoff. However, it will preserve engine life and
reduce fuel consumption over time.
The majority of engine wear will occur at higher
temperatures. For instance, a 1%
reduction from full take off thrust will result in a 10% saving in
engine life. The first few
degrees are the most damaging.
Consistent use of reduced thrust will more than double engine
life and prevent rapid performance deterioration.
- Reduced thrust is also important on the first flight of the day when the
engine core is cold. When possible, avoid the use of engine anti-icing
during takeoff as it will further increase the engine operating
temperature (EGT).
- Avoid using full thrust at the first sign of a slight tail wind. When calculating the required takeoff
power, consider the tail wind component.
In most cases, it will require a decrease of a few degrees in the
assumed temperature and will still permit some reduction from full
thrust.
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- INITIAL CLIMB OUT PROFILE MANAGEMENT
- Note: The following departure procedures must be compatible with local
noise abatement procedures.
- Speed and flap management on departure will greatly impact fuel
consumption and flight time. Once the flight is airborne, the flaps and
slats should be retracted as soon as possible. Although the flaps and slats increase
lift, they also increase drag and therefore increase fuel consumption
- However, when departing in a direction opposite to the desired enroute
course, there may be some advantages to maintaining the takeoff flap
setting and trading speed for altitude until the aircraft reaches the
initial altitude where a turn to the on-course can be initiated. This
will minimize the distance away from the intended direction. It will also maintain a lower speed
and allow for a faster turn rate to the on-course for a specific bank
angle (when possible use bank angles of up to 30 degrees). When the
flight is within 90 degrees from the intended course, flight crews
should accelerate to normal climb speeds.
- If a flight is departing away from the intended course, and a turn
cannot be initiated before a certain point from the departure course,
then cleaning up the flaps and slats will improve departure
efficiency. Speed should not be
increased above minimum clean drag speed until the aircraft is within 90
degrees from the intended course.
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- LATERAL TRACK MANAGEMENT
- Most efficient flight planning systems will consider all possible routes
or portions thereof to determine the most efficient routing between the
airport of origin and the destination including the planned departure
runway and procedures, winds, temperatures at altitude, airways
restrictions, NOTAMS, restricted areas, arrival procedures and expected
landing runways, etc. The cost of
airways and overflight charges must also be considered.
- The problem with many flight-planning systems is that the route analysis
is based on a fixed Mach number analysis of minimum time tracks. That is
very simplistic and the ultimate objective of the system should be to
find a minimum cost route based on Cost Index, looking at the route
possibilities vertically and laterally. Higher Cost Index values will
tend to drive altitude selection to lower Flight Levels due to the
higher True Air Speed values, assuming the system is optimizing based on
Cost Index and not on simplistic parameters.
- Failure to monitor overflight charges can result in several thousands of
dollars in additional costs.
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- Crews should attempt to fly the planned track as closely as possible
while taking some short direct routings to minimize large turns at
waypoints. It is important to adhere to the general routing of the
flight plan. When accepting a long direct routing, there is also the
danger of crossing restricted or military areas and when in doubt, it is
desirable to adhere to the planned routing.
- On long flights, there could be some value in reevaluating the routing
because after several hours of flying, the wind forecast might have
changed. Re-planning and
re-filing the route after departure can be difficult for the crews. ATC services will generally not accept
changes to the planned route from the ground when a flight is airborne.
In some cases, if the actual winds turn out to be different than those
forecasted - a rare case in today’s modern flight planning systems with
accurate wind and temperature data - there might be some value in
re-optimizing the whole flight plan and routing.
- The use of pre-determined routes and altitude capping should be avoided
and the route optimized according to the flight conditions for the day
of operation, unless required due to heavy traffic, specific local
procedures, or restricted by a preferred ATC route system.
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- VERTICAL PROFILE MANAGEMENT IN CRUISE
- Planning the most efficient vertical profile offers great potential
savings. An accurate flight
planning system will produce the best vertical profile based on the wind
field at each waypoint, the aircraft weight, temperatures and the flight
specific Cost Index (assuming the airline is using the correct Cost
Index values adapted to its cost structure and the flight planning
system incorporates Cost Index values in its altitude selection
process).
- Flight planning systems normally look at all available altitudes to
achieve the minimum cost per ground mile. A properly optimized flight plan will
provide the best altitude profile to be flown for the current mission
conditions. This may include descents to lower altitudes to take
advantage of better wind / TAS combinations.
- In the case of a flight being forced to deviate from its flight planned
altitude profile, the wind values for the next usable flight levels
above and below the planned altitudes should be available to assist the
crew in making tactical decisions.
If forced away from the planned altitudes, crews should attempt
to return to the flight planned vertical profile as soon as the
restrictions are cancelled.
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- Use FMS suggested optimum altitudes with care. Unless the wind field (including winds
above and below planned altitudes) and temperatures at the planned
waypoints are accurately inserted into the FMS by either an automatic
download or manually, the recommended FMS optimum altitude will be
incorrect. Some older FMS
versions will recommend a flight level based on weight regardless of
winds or Cost Index. In the case of older generation or regional
aircraft without FMS altitude information available, the Aircraft
Operating Manuals simply recommend altitudes normally based on weight
for LRC speeds (no wind or Cost Index input).
- Performance advisory systems are available for non-FMS aircraft, which
enable the use of Cost Index speeds and altitude optimization. These
systems are available in either in a booklet format, electronically as
part of the Electronic Flight Bag system (EFB), or in a stand-alone
system. Ideally, the optimization
from these systems should be integrated to the flight planning system
for greater flight planning accuracy and optimization.
- Cost Index optimization will result in substantial fuel and time
savings, while balancing the time and fuel costs for a specific airline
cost structure. They would also permit the use of tactical Cost Indices
for day-to-day operation to accelerate flights when adverse winds are
impacting on the on-time performance or during delays when several
passenger connections are affected. The use of lower Cost Index values
should also be available to
reduce speed for flights arriving early thereby reducing fuel
consumption and minimizing the chances of gate holds and possibly ramp
congestion.
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- If a flight is restricted to a lower than planned altitude for a
significant time period such as ocean crossings, allow the Cost Index to
determine the best Mach for that altitude. This process may result in additional
time costs; however, there will be significant fuel savings. In some
extreme cases, it might even allow for the completion of the flight
rather than diverting for fuel.
- If the actual aircraft weight differs significantly from the
flight-planned weight, the best option is to re-compute the flight plan
to achieve a better optimized vertical flight profile.
- On short flights, the most efficient vertical profile would be to
continue climbing until intercepting the descent profile. However, this
is not always practical. Most
optimum altitude data for short flights will assume a minimum cruise
time of 5 minutes. Total air distance should be considered when
selecting the optimum altitude on short flights, including the departure
and arrival runways and procedures.
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- CRUISE SPEED MANAGEMENT
- In normal cruise conditions, FMS equipped aircraft should produce an
optimized Mach number based on the selected Cost Index, the aircraft
weight, altitude, temperature and wind conditions. The Cost Index should
not be changed to control the Mach number. As the winds, weights and FL change,
regardless of how well they match the flight plan, allow the FMS to
compute the best Mach number.
- The above assumes that the Cost Index selected is properly optimized for
a specific airline’s cost structure.
Manually overriding the FMS speed will normally result in a loss
of efficiency either in time, fuel or both.
- Several aircraft types do not have FMS speed optimization. In this case, either a fixed Mach
speed or Long Range Cruise (LRC) speed is typically used. LRC speed is
equivalent to 99% of the Maximum Range Cruise (MRC) fuel burn but it
does not account for the wind effect. Again, there are optimization
systems, paper or electronic, which provide an optimized Mach and
improve the cruise efficiency from about 3 to 7% depending on flight
conditions and altitude.
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- The Cost Index selected for a flight should be based on actual airline
cost structure. It should also be
route specific since the price of fuel will often vary at each origin
airport. However, the use of “non
standard” Cost Index values can be used if the flight conditions for
that day are different than the average.
Higher head winds, last minute delays, curfews, slot times, gate
constraints, down-line impact of on subsequent flight, etc. can increase
a delay costs and the use of higher than normal Cost Index can be
utilized to minimize the delay cost. On the other hand, for an early
arrival situation, a lower than “standard” Cost Index can be used to
reduce the speed of an early flight.
This will save fuel and prevent possible gate holds, ramp
congestion, and additional ground staff costs.
- While the cost of fuel should be minimized, other costs must be
considered when selecting a specific mission Cost Index. Post departure
re-optimization of the flight speed profile should be considered to
reduce other time related costs.
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- COST INDEX MANAGEMENT
- Cost Index is the ratio of the cost of time over the cost of fuel. When
entered into the FMS, it optimizes the flight profile to balance the
cost of time (crews, aircraft time based maintenance, etc) against the
cost of fuel. For instance, if
time is not a factor (Cost Index= “0”), the use of cost index 0 would
optimize the flight for minimum fuel burn taking into consideration the
aircraft weight, altitude, temperature and wind conditions. If time is critical and the flight
must be conducted at minimum time, then Cost Index 999 (or the maximum
for a particular aircraft type) would yield the minimum time flight but
at the expense of significant increase in fuel consumption. Note
carefully that in an optimal system that is not simply a case of “going
fast”. Rather, it is a complex optimization of the winds at different
flight levels with the TAS values at those levels (and if in the flight
planning system, also considers the routes) to produce a true minimum
flight time scenario, but at a minimum possible burn for that flight
time. That is why Cost Index is used - the result is an optimal
solution; minimum possible burn for the flight time, or minimum flight
time for the burn.
- Cost Index “0” should seldom be used because cost of time is usually a
factor. A tactical exception would be an in-flight delay, such as a
hold. In that case, use of Cost Index zero (or even slower) will be
appropriate. Cost Index values at
the maximum limit are also used less frequently, however, if
circumstances support the cost of the fuel, then it is worth the extra
fuel burn for the flight time savings.
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- Airline that maximize the use of Cost Index will conduct a study of all
time related costs and determine the best default Cost Index for
day-to-day operation. Since the
cost of fuel differs from airport to airport, the default Cost Index
should be route specific.
- Because the flight schedule will subsequently have an impact on the
speed at which flights are operated on the day of flight, the scheduled
flight times should be based on speeds derived from the route specific
default Cost Index. It is very important that airlines spend the time
and effort to properly determine the most cost efficient value to
minimize overall cost.
- There are, however, other time related costs that occur during the
day-to-day operation that would justify not using default Cost Index.
Stronger than usual headwinds or a last minute delay can affect several
connecting passengers, impact subsequent flights with short turn around
times, miss a curfew or a slot time, create gate occupancy conflicts,
crew legalities or connections.
As can be seen, the cost of time can vary and the use of other
than default Cost Index values will help minimize the time related costs
even though additional fuel could be consumed in the process.
- Flight crews are normally in a difficult position to decide on the most
appropriate Cost Index for the flight.
Flight dispatch or Operations Control must proactively plan and
monitor of the flight progress.
- Finally, whatever airlines decide to do, they must ensure that all
processes are well defined, managed and fully integrated. Furthermore,
the value of effective training cannot be overemphasized. These
processes can be somewhat counterintuitive and compliance will be
somewhat proportional to understanding.
- The benefits of a well thought out performance optimization program are
significant.
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- FMS DESCENT PROFILE MANAGEMENT
- A properly planned and executed descent offers the greatest opportunity
for fuel savings. The ideal profile is an uninterrupted descent from
cruise altitude without the use of thrust or speed brakes until reaching
the final approach stabilization altitude. Adhere as closely as possible
to the computed descent speeds and monitor the decent profile to
determine as early as possible if adjustments are required. If above
profile, correct by increasing speed rather than using speed brakes. If
below profile, correct by reducing descent speed slightly to regain
profile or make power adjustments for profile correction as high as
possible.
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- FMS Descent Profile
- FMS systems can compute accurate and efficient descent profiles. Except
for tactical reasons, do not intervene by descending early or late, or
otherwise by modifying speeds and descent rates. In the final approach area, avoid
taking flaps early and use the minimum drag speeds when conditions
permit. The need to intervene may be necessary in certain situations but
unless the profile is modified by ATC, it should be flown as planned.
When possible, allow the technology to do what it was designed to
accomplish.
- To be accurate and efficient, the FMS should be allowed to manage the
descent profile, The number one rule in programming the FMS is to enter the approximate
descent and approach pattern which will most likely to be flown,
especially the first altitude restriction to be met. Otherwise, the top of descent point
computed by the FMS profile will be erroneous and the aircraft’s energy
state in the terminal area will be incorrect.
- Energy management is of the utmost importance during the descent profile
and the approach. Failure to properly program the FMS will undermine the
crew’s confidence in the system and may lead to a destabilized approach
by placing the aircraft too high on close final.
- Monitoring the previous traffic clearances may provide some clues to the
restrictions that can be anticipated.
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- FMS Descent Profile
- FMS systems can compute accurate and efficient descent profiles. Except
for tactical reasons, do not intervene by descending early or late, or
otherwise by modifying speeds and descent rates. In the final approach area, avoid
taking flaps early and use the minimum drag speeds when conditions
permit. The need to intervene may be necessary in certain situations but
unless the profile is modified by ATC, it should be flown as planned.
When possible, allow the technology to do what it was designed to
accomplish.
- To be accurate and efficient, the FMS should be allowed to manage the
descent profile, The number one rule in programming the FMS is to enter the approximate
descent and approach pattern which will most likely to be flown,
especially the first altitude restriction to be met. Otherwise, the top of descent point
computed by the FMS profile will be erroneous and the aircraft’s energy
state in the terminal area will be incorrect.
- Energy management is of the utmost importance during the descent profile
and the approach. Failure to properly program the FMS will undermine the
crew’s confidence in the system and may lead to a destabilized approach
by placing the aircraft too high on close final.
- Monitoring the previous traffic clearances may provide some clues to the
restrictions that can be anticipated.
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- Distance, speed and altitude trade off
- Generally, the following rules can be used for a quick calculation
between distance, speed and altitude trade-off:
- An aircraft in clean configuration and at idle power will decelerate 10
knots per nautical mile when in level flight. i.e. 60 knots speed loss will require
about 6 NM
- In a clean configuration and at idle power, an aircraft will descend
1,000 feet per 3 NM
- A flight that has decelerated 60 knots when in level flight and
subsequently regains initial speed will lose 2,000 feet (1,000 feet per
30 knots) during acceleration to previous speed.
- For example, flights arriving downwind from the landing runway could
most likely receive an altitude restriction to cross downwind from the
airport at about 6,000 feet. If
any kind of tailwind exists on the downwind leg or if a Visual Approach
is expected, the flight, from an energy standpoint flying at 6,000 feet
and at 250 knots, for certain aircraft types (B767, A320) would be high
on the profile and need extra drag to complete the approach.
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- If the speed abeam the airport while at 6,000 feet is reduced to 190
knots instead of 250 knots, the aircraft’s energy level would be
equivalent to that of crossing the abeam point at 250 knots but at 4,000
feet. At 190 knots, 9 NM would be required to descend from 6,000 feet to
3,000 feet and this would place the aircraft in a good position for an
energy efficient approach when turning on final. Otherwise, the need to
reduce speed from 250 knots to 190 knots and descend at the same time
would make the aircraft too energy rich and would require the use of
speed brakes.
- Closely monitor the energy level of the flight and make the appropriate
adjustments to avoid continuous alternating use of thrust and speed
brakes during descent and approach.
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- Descent Profile Wind Corrections
- A clear understanding of the FMS Vertical Navigation (VNAV) capabilities
will permit the crews to establish a much improved descent profile. For
a more accurate FMS computation of the descent profile, insert the
descent winds. If the descent winds are not entered in the FMS, a wind
profile will be built assuming a constant decreasing wind speed from the
cruise level down to the airport altitude. On some aircraft, the computed descent
winds at each waypoint can be seen on the flight plan page and can be
compared to the forecast winds.
If they are found to be significantly different, then the
forecasted winds should be updated in the FMS.
- Chances are that the descent winds will vary from the assumed wind
profile built by the FMS. If the winds are noticeably different than
those computed by the FMS, like in the case of a jet stream or
increasing winds after the descent is initiated, the pilot can,
re-select the Direct To function to the active waypoint after the winds
stabilize. This allows the FMS to recalculate a new wind profile and
descent vertical flight path using actual winds from the present
altitude and will create a new possibly more accurate descent profile.
- It is important to take corrective action as high as possible to allow
sufficient time for the extra energy to be burnt off with additional
speed in case of an increasing tailwind or to regain the proper profile
as high as possible with increased thrust when in an increasing
headwind.
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- Landing Weight
- Higher landing weights will increase the descent distance for the same
descent speed since it takes longer to dissipate greater potential
energy. However, if the descent speed is increased, then the additional
energy will be absorbed by the increased drag and the descent angle will
then be increased. For instance, competition gliders will carry water
ballast to increase speed while maintaining the best angle of attack.
Some modern FMS systems will vary the descent speed in accordance with
landing weight. Other optimization systems will account for the landing
weight while computing the descent profile.
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- Engine Anti-Ice
- On some aircraft types (Airbus 330, Boeing 767, etc.), the engines will
automatically spool up upon selection of engine anti-ice. In some cases,
this can force the aircraft above the computed descent profile as the
increased speeds might not be sufficient to absorb the extra energy.
- When engine icing is anticipated, for the aircraft which do not account
for the use of engine ice on descent, plan a lower than desired descent
speed in the FMS for profile computation purposes. The increased speed resulting from the
use of engine anti-ice will bring the descent speed closer to the
desired descent speed.
- If the flight is on profile when the engine anti-ice is selected,
attempt to increase speed rather than using speed brakes to absorb the
extra energy.
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- ATC Restrictions
- When on descent profile, if the descent is interrupted temporarily
forcing the aircraft above profile, slow down as much as possible while
in level flight and then trade the surplus altitude to subsequently
regain the descent speed and profile. This minimizes the chances of
subsequent use of speed brakes. This could be subject to ATC
restrictions depending on circumstances.
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- Penalties for Early/Late Descent
- Profiles that commence too early or too late cause a significant
increase in fuel usage.
- f one is to err, it is better to be slightly early on descent, rather
than late. If one starts down early, the opportunity of regaining the
optimum profile is available and it should be done as high as possible.
If the descent is started too late, then the fuel has already been
consumed by remaining at altitude and it can never be recovered since
the extra energy must now be dissipated with increased drag. Ideally, the descent profile should be
planned correctly. Some crews
tend to always undershoot target altitudes for comfort. Appropriate programming of the Flight
Management Systems should enable the aircraft to accurately be on profile.
- Note: There is obviously a greater use of speed brakes for crews who are
new on an aircraft type or have less experience on heavy jets but speed
brakes should not be a substitute for adequate descent profile
management and overall planning.
- The goal is to reach the initial approach point at the right altitude
and the correct speed without the use of speed brakes or power. Ideally, the descent should be
uninterrupted.
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- BASIC PRINCIPLES OF THE DECELERATED APPROACH
- The most fuel-efficient arrival allows the descent profile to flow
unrestricted into final approach without the use of engines thrust or
speed brakes. The following
should be considered:
- Since normally the descent speed below 10,000 feet is limited to 250
kts, that speed should be maintained until ready to reduce speed to the
minimum drag clean speed in preparation for the approach phase.
- When feasible, use or request speed vectors to prevent excessive
distance travel to establish the aircraft on final approach. This will
often require some initiative by the crew. Remember that most aircraft
have a significant speed margin of almost 150 knots between VMO and
clean maneuvering speed during the descent phase.
- Keep the aircraft clean! Flaps and slats are not designed as drag
devices for slowing down but to produce lift. In the process, there is
a significant drag increase. Continuous extension of flap at near
limiting speeds also increases the risk of component failure. Note that
ATC might not always be aware of the clean maneuvering speed for your
aircraft type. Often a word to
them will save an unnecessary early flap extension. Don’t be afraid to
retract the flaps should the approach be extended
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- Request the arrival sequence number from the Approach Controller on
initial contact. This makes it easier to estimate the distance to touch
down. Decide how to manage the energy and whether to slow down early to
minimum drag speed to prevent excessive downwind vectoring.
- Avoid dumping excess altitude too early or use of speed brakes to a
cleared altitude and then having to add power to fly level at that
cleared altitude for an extended period of time
- Unless assigned a hard speed by ATC or by a specific procedure, do not
hesitate to use speed control to best advantage
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- FMS Arrivals
- Many airports use FMS arrivals. A
well-designed FMS arrival should allow a flight to descend and maneuver
with the engines at idle and the engines ‘spooling-up’ at the final
approach fix, thus saving fuel.
- Visual Approaches
- Although ATC expects the FMS arrival to be flown as planned, it is
sometimes possible to perform a Visual Approach from the downwind
leg. A Visual Approach will save
some additional fuel. Calculations indicate that in some cases, fuel
savings associated with Visual Approaches equal a total of 2 minutes at
idle power fuel flow (20 kg for the A320/B737). The distance traveled is
reduced by approximately 3 miles for each of the downwind and final
approach. The aircraft is assumed to roll out on final approach at
approximately 2 miles back from the FAF when conducting a Visual
Approach.
- The Visual Approach offers an opportunity to best optimize all of the
above recommendations. During FMS approaches, which are designed for IFR
conditions, the use of a Visual Approach will normally result in
additional savings.
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- Decelerated Approaches (Low Noise Low Drag)
- Although this is an Airbus recommended procedure, it applies to most
aircraft types. The Low Noise/Low Drag approach has been used to
minimize noise in several countries for many years. The basic principles apply to other
aircraft types with minor variations depending on specific
characteristics.
- The advantages of the Decelerated Approach are as follows:
- Lower fuel consumption and emissions
- Lower noise levels
- Time savings
- Flexibility and ability to vary speed to suit ATC
- Another advantage of using the Decelerated Approach is that it sets some
clearly defined target altitudes and speeds to achieve during the
approach. After a few approaches, it will result in improved standards
because most approaches at various airports will be completed in an
identical manner. Presently, many
crews will start flap selection at a distance that varies from over 20
miles to less than 5 miles from touchdown with little consistency from
one approach to another.
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- In the case of the Decelerated Approach, the slats and flaps selections
are mainly a function of altitude above the ground rather than a
distance to the touch down point.
This permits improved energy management during the approach.
Using the Final Approach Fix (FAF) to establish the stabilization
altitude will lead to inconsistencies as the FAF can be located at a
distance which can vary greatly from the runway threshold.
- Basically, the aircraft is kept in a clean configuration with the speed
reducing to minimum drag clean speed until base leg or prior to turning
final at approximately 3,000 feet above ground. At that point, the
initial slat selection is made and the speed adjusted to the slats only
minimum drag speed.
- If the aircraft intercepts the glide slope above 3,000 feet, slats/flaps
selections should be delayed until reaching that target altitude. The ability to maintain speed on the
glide slope in a clean configuration will depend on the aircraft type,
the landing weight and the wind component. If possible, use speed brakes
to control speed rather than flap or gear extension to control speed.
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- The next target is 2,000 feet AGL where the initial trailing flaps are
selected (approximately 15 degrees depending on the aircraft type). This normally occurs just outside the
Final Approach Fix and a gradual reduction toward the final approach
speed is started. When the flaps
have reached their intermediate position, the landing gear is lowered.
- The final landing flap selection is made to achieve approach
stabilization by 1,000 feet AGL.
Note that the flight should be configured at the approach speed
by 1,000 feet AGL. If by 500 AGL,
the flight is not fully stabilized, a Go-Around should be considered.
- Flight crews will quickly become familiar with the Decelerated Approach
and significant fuel savings will result.
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- High Head Winds on Final will result in long final legs
- When high winds (30 knots or more) are encountered on final approach,
its effect on the intermediate approach pattern can be significant.
Slower traffic will often cause the subsequent traffic to back up and
will result in very long final approach legs at low speed in a high drag
configuration.
- When this is anticipated, subject to ATC restrictions, the crew should
attempt slow down as soon as the situation is recognized (normally early
downwind). All speeds above minimum drag clean speed should be traded
for altitude even if that will make the flight appear high on final. The
flight will likely end up on a long approach and the extra altitude can
be used up once the flight is turned toward final. It is not difficult
to eliminate excess altitude on final approach when headwinds winds are
strong.
- The idea is to reduce speed early, when possible, to minimize excessive
downwind travel and getting into a high drag configuration while on the
final approach in a strong headwind. This is extremely inefficient and
will consume a significant amount of fuel during the final leg.
- Slowing down early will improve the possibilities of maintaining the
aircraft in a clean configuration as long as possible once on final. At
this point, the previous traffic would have had time to move forward.
This should help position the flight for a low drag approach, which is
even more critical in a high head wind situation.
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- REDUCED FLAP LANDING
- Most airplanes are certified to land without using full landing flaps.
Some aircraft types even have auto-land capability while using reduced
flap settings. When conditions
are appropriate, landing at less than full flap has some definite
advantages. At the last flap setting more drag than lift is normally
generated. Reduced flap landings
will not only reduce fuel consumption but also decrease chemical and
noise emissions. When landing an
airplane with reduced flaps, fuel burn is reduced by approximately 25 kg
in fuel on an A320/B737 landing and 50 kg for an A340/B777 size
aircraft.
- Some of the factors to consider when performing a reduced flap landing
include:
- The landing weight;
- The runway length;
- The runway exit point and occupancy time;
- The runway surface conditions;
- Possible tail wind component on final approach; and
- Brake cooling during short turn around times
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- The average increase in speed for reduced flap is landing is
approximately 5 knots and the extra landing distance around 500 feet.
- Several airlines have made reduced flap landing procedures a standard.
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- IDLE ENGINE REVERSE ON LANDING
- With the ever increasing price of fuel and environmental considerations,
the use of idle engine reverse should be used whenever possible. The main advantages of using idle
reverse on landing include:
- Reduction in fuel consumption;
- Reduction in environment emissions;
- Reduction in noise emissions;
- Better passenger comfort;
- Elimination of a high power cycle on the engines;
- Reduction of foreign object damage (FOD);
- Reduction in potential engine stall and re-ingestion;
- Increased engine reliability;
- Lower cooling time requirement before shutting engines down for
engine-out taxi; and
- Slower engine performance deterioration.
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- Most modern aircraft now use carbon brakes. Brake wear is more a
function of the number of applications rather than the amount of braking
used. Carbon brakes can withstand higher temperatures without loss of
efficiency or fading. In the case of an airplane equipped with
auto-brake capability, the braking selection will determine the rate of
deceleration, and the stopping distance is generally identical to
landing with full reverse thrust.
- When using idle reverse on landing, the following factors should be
considered:
- Runway length and aircraft landing weight;
- Tailwind on final approach;
- Runway surface condition;
- Touch down point; and
- Turn around time.
- On long runways, idle reverse thrust can decelerate the aircraft
sufficiently without using the brakes.
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- ENGINE-OUT TAXI-IN
- Under normal conditions, engine-out taxi-in should be a standard
procedure. SOPs that are well designed encourage engine-out taxi with
minimal work for the flight crew.
When using the engine-out taxi procedure, anticipation is
important and the aircraft must be kept moving. Flight crews will require training and
familiarization with engine-out taxi procedures. Crews familiar with engine-out taxi-in
procedures follow the procedure after almost every landing. The main advantages are the following:
- Reduction in fuel consumption;
- Reduction in pollution; and
- Reduction in brake wear.
- Consider the following before apply engine-out taxi-in procedures:
- Taxiway surface conditions;
- Taxi-in time;
- Ramp congestion; and
- Local airport regulations.
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- FLIGHT SCHEDULE AND FUEL MANAGEMENT
- Based on an accurate airline cost structure, an optimized schedule takes
into account efficient aircraft speeds.
Airlines must use rationale business-based methodologies for
establishing optimized Cost Index values (CI) for each aircraft type
equipped with Flight Management Systems (FMS) or with other onboard
systems capable of CI optimization.
The CI should reflect a balance between the fuel cost and other
time-based costs specific for the airline and, when the business
processes support it, the specific flight based costs. Since the price
of fuel is normally different at each departure airport, the specific
flight CI should reflect the price differential.
- Cost Index is a function of time cost over fuel cost. Flying with a high
CI will increase aircraft speeds and may result in flying at lower
altitudes, depending on conditions. The increased fuel costs are offset
by a reduction flight time related costs. A low CI increases the flight
time costs, and results in flying at higher altitudes, however it
consumes less fuel.
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- For example, a B767 using a very high CI (inappropriately high for the
actual corporate time costs in this example) on a 6-hour flight might
result in the flight burning 3 tons of additional fuel (US$1500)
relative to a flight plan at the correct Cost Index. The time saved at
the high Cost Index could be, for this example, 20 minutes flight time
worth US$1,000 (1/3 of $3,000 / hour time cost for rental, maintenance,
crew, etc.). It would result in a US$500 loss for that flight due to the
high cost of fuel compared to value of extra time saved. Using a
much-reduced CI, (compared to the hypothetically correct for the
airline’s actual cost structure), the operator could reduce the fuel
burn by $1,000 but increase the flight time by 15 minutes ($750) thereby
reducing the total flight cost by $250. One might want to consider the
fact that additional fuel burn in some cases might be cost effective
when dealing with of late or oversked flights with numerous connections,
curfew or slot restrictions, and impact of the delay on subsequent
flights, etc.
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- CALCULATION OF SAVINGS
- Air Traffic Control
- The impact of Air Traffic Control on fuel consumption is covered
elsewhere. However the following can have a marked effect on fuel
consumption:
- •Excessive Government regulations;
- •Poor ATC route structure;
- •Excessive ATC restrictions for no specific reason or for ATC
controllers’ convenience;
- •Lack of sufficient ATC staffing;
- •Poor equipment;
- •Inflexible noise abatement procedures; and
- •Inadequate communications.
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- Pilot Technique
- Through analysis of Fuel Management Information systems, which
accurately captures achieved flight performance, it can be demonstrated
that the fuel performance of various crews can vary on average from plus
or minus 2.5% from planned fuel burns.
This can be even more pronounced on short-range flights where a
significant portion of the flight is spent maneuvering. Proper training,
emphasis on fuel economy, adequate SOPs, proper management leadership
and accountability will greatly impact fuel performance. It may be
possible to save at least 1% to 2% in fuel consumption if the crews
consistently apply all the following fuel saving procedures:
- •APU management;
- •Efficient start up and taxi speeds;
- •Engine-out taxi out;
- •Departure runway selection if possible;
- •Speed control and altitude trade off on departure;
- •Post departure flight profile optimization;
- •Cruise altitude and speed management process;
- •Descent profile planning and management;
- •Low noise low drag approaches procedures;
- •Reduced flap landing;
- •Idle engine reverse on landing;
- •Engine-out taxi in.
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- Cost Index Flying
- Cost Index optimization should be the basis for the optimization of all
airline flight operations. The reason is simple; optimal profiles burn
the least amount of fuel for a given flight time or, conversely, they
have the shortest flight time for a given amount of fuel burn.
- The best way to plan and fly “optimal” profiles is to use a Cost Index
optimization system, both at the flight planning stage and for real time
flight management in the cockpit. Airlines that make proper use of Cost
Index optimization at the flight planning stage, and on a day-of-flight
basis, will achieve the greatest savings.
- With any optimization system, the system optimizes to a target
parameter; in this case, the Cost Index. So, it is obvious that the Cost
Index, which is a ratio of the true time cost per minute to the actual
fuel cost, must be selected correctly. Since fuel costs, and in some
cases, time costs vary with the route, the Cost Index should be route
specific. Once an airline has made the internal effort to analyze their
incremental time costs, then the Cost Index for each route should be the
basis for their schedule construction and day-to-day operations. The
potential savings from Cost Index flying vary based on many factors.
However, total overall cost savings of approximately 3% - 5% is not
unrealistic, especially given current very high fuel costs and the fact
that most non-Cost Index flight profiles are rather aggressive and not
particularly fuel conservative.
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- When circumstances in the day-to-day operation would result in a flight
arriving significantly later than scheduled, (to the point where
connections, curfews, etc. would be jeopardized) then it may be
appropriate to use a higher Cost Index value to achieve a required
target arrival time to minimize these costs. It will result in significant
additional savings.
- The importance of using Cost Index to achieve these accelerated
profiles, rather than just “going fast”, is again related to the fact
that these profiles are optimal. This results in the achieved flight
time being the shortest, and the least amount of fuel-burn the least
possible using Cost Index. In the
case of misconnection related costs, these can be very significant and
in many cases, can be mitigated by the proper use of accelerated Cost
Index profiles.
- No other method of flying - including fixed Mach, multiple fixed Mach,
Long-Range Cruise - will result in optimal profile solutions.
Furthermore, these basic profiles also use simplistic altitude selection
methods. However, altitude is a critical component of the profile. Cost
Index solutions solve both the altitude and Mach number. By using Cost
Index profiles significant cost savings will result because of a more
efficient overall operation, based on both fuel and time based savings.
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- Accurate Flight Planning
- Airlines can save millions of dollars with the right guidance on cost
management, an accurate flight planning system, and properly trained
dispatchers. Optimizing each flight and avoiding pre-determined routes
or unnecessary altitude capping will save a significant amount of fuel.
An adequate flight planning system will:
- •Optimize the route laterally,
- •Vertically based on Cost Index,
- •Look at the enroute navigation fees, ETA (connections)
- •Will assess all possible combinations to come up with the minimum cost
(fuel and time) for a specific flight.
- Savings in excess on 1% to 2% are not unreasonable.
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- Using Statistics for Fuel Optimization
- Fuel in excess of minimum regulations should be planned carefully. The availability of statistics on the
additional fuel consumed above the flight plan burn on a specific city
pair based on time of day, day of the week, season, etc will yield
valuable information to both the dispatchers and crews. The information will help them
determine the right amount of fuel for the flight. In general, crews are in a difficult
position to assess the correct amount of fuel required for a flight
because of a lack of information on the actual traffic, the available
time to flight plan, aircraft turn around times, ATS special advisories,
frequency of flying that route, wanting comfort fuel, and lack of adequate statistics, etc.
Almost invariably, the fuel added by crews without coordination with the
dispatcher remains unused. Boarding additional fuel based on adequate
statistics will reduce fuel burn from 0.5% to 1%.
- Alternate Selection
- Diversions for modern aircraft flying to airports with sophisticated
ground equipment are a rare occurrence.
On average, diversions will occur about one in a thousand
flights. Normally, most of the
diversions are not weather related but are about one third for
mechanical reasons, one third for medical reasons and the rest for
weather. Most of the weather
related diversions were most likely anticipated based on the forecast.
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- It is therefore important to select the most efficient alternate based
on circumstances. This is assuming that a no-alternate IFR flight is not
possible. Many factors can affect the alternate selection. Airlines
should systematically review the availability of the closest alternate
for each destination. If the
chance of diversion is very small, then select the closest alternate
based on realistic distance to travel as per the anticipated ATC
routing. When the chance of
diversion increases, a more appropriate alternate should be planned
taking into consideration all factors that can minimize the impact on
the operation (see the alternate selection chapter for more details). An
efficient alternate selection process can yield savings of 0.5% to1% in
fuel not considering its impact on payload and other costs.
- Aircraft Fuel Burn Management
- As aircraft are put into operation, each airplane develops its own burn
characteristics. If we compare a new airplane to one which is the same
model and that has been in operation for a few years, you may see a
difference in the fuel burn in excess of 5%. Accurately tracking each
aircraft and adjusting flight plan fuel burns will reduce the carriage
of unnecessary fuel. This is particularly critical for long-range
airplanes. The failure to properly manage specific aircraft fuel burns
will lead flight crews to develop their own system and add fuel on just
about every flight. This lack of confidence in the planning system will
be very costly and can lead to an increase fuel cost in the order of
0.5% to 1%.
- Tankering
- Depending on circumstances, the potential savings from tankering will
vary between airlines. An adequate tankering process will yield
significant savings. Proper fuel supply management will prevent tactical
tankering, which is normally costly (see the Tankering section for more
details). An efficient tankering program should save airlines between
0.5% to 1% and more in fuel cost.
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- Zero Fuel Weight Management
- Proper estimation of the Zero Fuel weight is critical because it will
decrease the carriage of unnecessary fuel or prevent a possible last
minute delay for additional fuel.
It will also have a significant impact on the flight
profile. Again, poor EZFW
predictions will undermine the confidence in the flight planning system
and lead to the tendency to load additional fuel to compensate for
inaccuracies. Savings in the order of 0.5% to 1% are possible.
- Center of Gravity Management
- Flying with an aircraft loaded to the most forward Center of Gravity
will consume approximately 3% more fuel above baseline Center of Gravity
loading while flying with the most rearward Center of Gravity will
reduce fuel consumption by as much as 1.5% depending on the aircraft
type. Overall, properly managing the Center of Gravity will easily yield
saving in the order of 1% to 2% during line operation.
- Maintenance
- Aircraft maintenance impacts the efficiency of an aircraft. Engine
washes, flight control rigging, airframe buffing, paint condition,
engine overhaul, door seals, protruding controls, spoilers, doors, etc
contribute to the reduction of an airplane’s fuel efficiency. With
improved maintenance, approximately 1% – 2 % in fuel savings can be
realized. Refer to section 10 for more details.
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- Others savings
- Other savings related to ETA management, over fuelling, APU handling by
ground and maintenance staff can bring additional savings.
- Total potential savings
- Depending on the present efficiency status, airlines that proactively
manage fuel initiatives, and develop sensitization, training and
incentive programs have a potential fuel savings of 9% to 17%. Airlines
will yield great benefits with minimum investment if they review their
fuel management procedures, identifying all the areas of potential
savings and update their SOPs and training programs. The leadership has
to come from upper management and people have to be made accountable
especially Flight Operations managers.
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- MISSION MANAGEMENT
- The schedule
- Approximately 50% of an overall airline budget is consumed by actually
flying aircraft. Managers often assume that this is just the cost of
doing business when effectively there are many opportunities to improve
efficiency.
- An airline schedule will have a significant impact on efficiency. As
discussed earlier, developing a schedule based on speeds resulting from
the proper use of Cost Index optimization adjusted to the airline real
costs (fuel and time) is essential to achieving efficiency. The schedule will not only determine
the way flights are subsequently operated to maintain On-Time
Performance (OTP) but it will have a significant impact on the cost of
operating a flight (fuel prices, crews, fleet planning and aircraft
utilization, maintenance, connections, and so on).
- Therefore, assuming that the schedule is properly built, the next
challenge is how to manage a mission to minimize overall airline costs.
- The importance of accurate flight planning including the proper use of
Cost Index, alternate selection, discretionary fuel addition based on
appropriate risk management, tankering, etc, are discussed in other
sections.
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- On-Time performance
- Not only is On-Time Performance critical to customer satisfaction but
operating “on-time” will minimize disruption costs. While departing on time is very
important, arriving on schedule is even more critical. If a flight is planned with a forecast
late arrival, then an analysis of the late arrival costs should be made
to determine whether or not the time should be recovered in flight,
based on an analysis of the cost of the late arrival.
- Even early flights can increase cost, as they could have been operated
at a lower Cost Index thus reducing fuel consumption. In addition, early
arriving flights have other costs such as gate holds and utilization,
ramp congestion, additional ground staff, and so on. Late arriving flights on the other
hand will not only incur the above mentioned costs but can have a
serious impact on passenger and baggage connections, curfews or slot
times.
- The real cost of misconnections is most difficult to assess and will
depend greatly on circumstances.
If a passenger misses his connection but is accommodated on an
early connecting flight with empty seats - assuming of course that
passenger did not have serious time constraints on arrival - then the
impact of a delay can be minimal.
But if the passenger misses an important connection, which
negates the whole purpose of his trip, the consequences can be
serious. In addition, when the
passenger needs to be protected on another airline, most of the ticket
revenue can be lost.
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- Finally, the loss of “value passenger” goodwill is hard to measure but
may result in the passenger selecting other airlines for future travel.
Late flights will also impact baggage connections, which can be a
serious irritant for passengers. Some airlines spend millions of dollars
delivering baggage to irate passengers every year. Late flights can have
repercussions on numerous subsequent flights throughout the day and the
cost of a late flight can rapidly multiply several times.
- It is therefore of utmost importance to develop an On-Time Performance
culture not only for flight crews - but for every staff member,
including passenger agents, servicing crews, maintenance, and gate
planners, who can all influence the OTP. Staff has to be sensitized that
there are great costs associated with any delay at all.
- Managing the mission
- The tactical use of Cost Index will play an important part on fuel
consumption. Speeding up flights should not be a substitute for good
ground handling practices or on-time departures. However, if on the day
of operation, the winds are stronger than usual - and this will result
in a flight arriving late with all the associated costs of a delay - or
when a delay is anticipated and there is enough time to plan or
re-compute the flight plan, it might be better to speed up the flight
(higher Cost Index) when the cost of the additional fuel is less than
the anticipated delay costs.
- It is not always possible to increase the Cost Index sufficiently to
compensate for the whole delay - but its impact could be mitigated.
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- A close look at the connection distribution might yield a target arrival
time that is achievable and results in the minimum cost of operation.
This would normally be done at the planning level using proper cost
analysis tools. There is no point
speeding up a flight where there is no commercial value in doing so.
- One problem is when a flight encounters a last minute delay and the
decision must be taken to minimize the disruption cost. Crews are normally not in a position
to be able to assess such a situation although providing crews with a
list of connections will certainly raise awareness on their part. The
idea is to have the airline’s Operations Control department perform an
assessment and determine the course of action that will best minimize
the cost of a delay.
- Some connecting flights might also be delayed and therefore there is no
value in speeding up a flight to make those connections. Some other
connecting passengers could easily be accommodated on a later flight at
minimal cost. The idea is that each situation is different and must be
analyzed according to circumstances and on its own merit.
- The need for effective and timely coordination and communication
capability between Operations Control, Dispatch and station control and
flight crews cannot be overstated.
- The question is whether there will be additional fuel on board to
accelerate a flight in the event of a last minute delay. Airlines are normally aware of flights
that have critical connections. They are also aware that some of these
high commercial value flights are likely to experience last minute
delays. On those specific
flights, extra fuel should be boarded in spite of the additional cost of
carrying the acceleration fuel. It is equivalent to buying an insurance
policy. It could also in certain circumstances prevent a diversion of a
very high commercial value flight in case of a last minute hold on
arrival.
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- The question is how much additional fuel to carry. If a flight is
already accelerated because of adverse winds or for some other reasons,
there is no point carrying additional fuel as it cannot be used for
acceleration purposes. There is also a limit as to how fast a flight
should be accelerated.
- Airline policy should determine a maximum Cost Index beyond which
excessive fuel is consumed for little time gain.
- An adequate flight planning system should permit the calculation of all
costs associated with a specific flight plan including the available
flight time flexibility. If the payload is affected by the carriage of
additional fuel, a cost analysis should determine whether to protect the
payload or the connections.
- The flight crews
- Flight crews can play a major role in managing the flight.
- Being proactive to insure that flights depart on time is important. It
is important to arrive early to the aircraft so that crews can ensure
that there are no mechanical problems or Minimum Equipment List [MEL]
tasks to be performed, and brief the cabin crew on the need to be ready
for on on-time departure.
- The flight plan package should include a list of connections with the
connecting flights and departure times. While Operations Control and
Dispatch have numerous flights to handle, crews only manage one flight
at a time. They are often aware
of problems before other departments.
It is important to communicate and coordinate any change of
situation as soon as possible.
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- Start up and ramp departure procedures should be efficient. Some airlines have long and cumbersome
starting procedures that they block the ramp for 15 minutes or more,
causing a tie up for several other flights.
- Taxi speed should be reasonable. Valuable time can be lost by
excessively slow taxi speeds.
Crews that are consistently over schedule are probably loosing
the best part of the block time during taxi. Airline contracts often
have the strange characteristic of rewarding crews that are arriving
late (schedule growth) often for no identifiable reasons.
- Once the flight is airborne, the arrival time can be estimated fairly
accurately. If it is determined
that the flight will be late at planned speeds, the crew should advise
Operations Control or Dispatch of the forecast arrival time and a cost
analysis of the late arrival should be performed. If it is decided that
the flight should be accelerated, a new optimized flight plan should be
computed with a new profile and Cost Index, depending on the fuel
available.
- It is critical for the crew to update the Estimated Arrival Time (ETA)
as soon as possible to facilitate the ground coordination such as gate
planning, meeting the flight by ground crews, passenger agents to assist
with tight connections and rearrange missed connections.
- An accurate ETA might also allow Operations Control to delay some
connecting flights and subsequently accelerate these flights keeping
service to customers in mind while minimizing operating costs.
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- COST INDEX COMPUTATION
- The Cost Index (CI) is a ratio between the costs of time versus the cost
of fuel. Ideally, an airline should balance all its operating
costs. For instance, operating at
very high relative Mach will increase the fuel cost but the time cost is
lower and conversely, at lower Mach, the fuel cost is reduced but time
cost increases. So how are these costs balanced?
- On-board Flight Management Systems or other flight profile optimizing
systems can calculate the Mach number and altitude to balance the time
cost with the fuel cost once the time versus fuel costs ratio (Cost
Index) is known. This is why
establishing a proper Cost Index for each aircraft type for a specific
airline cost is critical.
- How can this be done?
- By determining the various time and fuel costs, it is possible to
determine the most efficient CI for a specific aircraft type based on
the airline’s cost structure.
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- Let’s try an example using metric Cost Index units for an b737:
- Cost Index = Time Cost / Fuel cost
- The time costs include any item where the flight time has a direct
impact on cost such as crew cost, incremental maintenance costs, etc. It
is normally expressed in $/min. e.g.:
- Crew cost
$ 7/min
- Incremental maintenance $15/min
- Total time cost
$22/min
- The cost of fuel is expressed in $/Kg
e.g.: $0.60/kg
- So the Cost Index should be $22/min divided by $0.60/Kg = a CI of 37
- As can be seen, airlines that have low time cost structure and high fuel
prices should operate at low CI and consequently lower speeds and visa
versa. Since the price of fuel is different at every airport, it would
be reasonable to adjust the CI to be route specific.
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- FUEL MANAGEMENT INFORMATION SYSTEM (FUEL MI)
- A well-structured Fuel MI enables airlines to track accurately all
aspects of fuel usage. It should
compare flight-planning information with actual flight data for
analysis. A well-structured Fuel MI system should enable the monitoring
and analysis of the following areas:
- Monitoring the accuracy of the flight planning system
- The Fuel MI should include sufficient data to monitor the accuracy and
integrity of the flight planning system. Confidence in the accuracy of
the flight planning system will go a long way to reduce unnecessary fuel
additives.
- Tracking of each aircraft fuel burn accurately
- Flight planning systems normally use a performance correction factor to
match the system with the individual aircraft performance. The ability
to track each aircraft accurately is of the utmost importance
particularly for long-range flights.
In the case where 100 tons of fuel is consumed during a
long-range flight, a 1% error in planned fuel burn performance can
result in the carriage of one ton of unnecessary fuel. This could also affect as many as 10
passengers or reduce cargo by one ton. In some cases, it could force an
enroute fuel landing or arriving at destination with less than
regulation fuel.
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- Precisely tracking and managing an aircraft’s specific fuel-burn is
critical. It will prevent flight crews from making their own subjective
burn corrections, if they have no confidence in the accuracy of flight
planning system.
- Note: Performance correction factors will need adjustments during
initial aircraft introduction to match the manufacturer’s claimed
performance with the optimization algorithm of the flight planning
system. It will also need periodical adjustments during periods of heavy
crew training or seasonally for situations such as winter operations,
and so on.
- Monitoring Fuel on Board (FOB) and fuel uplift
- Ask these questions: Is the fuel boarded accurate? Is the fuel billing
accurate?
- Tracking of fuel uplift will ensure proper invoicing. Do flight crews
add fuel without coordinating with flight dispatch or load control? Unplanned additional fuel boarded will
result in non-optimized vertical and lateral profiles.
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- Re-fuelers also have a tendency to board more fuel than required. Here are some frequently encountered
situations and arguments from re-fuelers:
- That crews like a little extra fuel.
- “Traffic is heavy today”
- They did not want to reconnect for a couple of hundred of kilograms of
fuel
- The fueling gauges at the refueling station are different from the
cockpit
- Their supervisor told them to always board additional fuel
- It is nice to have a round number for cross checking calculations, etc.
- In some cases, boarding fuel in excess of plan can exceed the aircraft’s
Maximum Takeoff Weight (MTOW), resulting in denied boardings, the need
to de-fuel or departure delays.
- Depending on the aircraft type, experience has demonstrated that an
average of 200 kg per flight (60 USG) is boarded above the planned
fuel. This tendency of over
fueling flights will consume 32 metric tons per aircraft of additional
fuel based on an annual utilization of 4,000 hours per year. It will also cost almost $US 16,000
for carriage alone not considering the potential revenue loss and wear
and tear of the aircraft.
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- Monitor the Fuel over Destination (FOD)
- Tracking the FOD will help monitor the flight planning efficiency and
measure the carriage of unnecessary fuel. It will facilitate the
development of a statistical approach to fuel planning and provide
guidelines to flight crews and dispatchers when boarding additional
fuel. Remember, excessive landing fuel will increase wear and tear on
the aircraft (brakes, engines).
- An accurate Fuel MI will facilitate the monitoring of airports where
there are significant variations from the planned landing fuel and
ensure that sufficient fuel is carried to avoid possible diversions.
- It will highlight the cost of designating excessively long alternates
when planning. Some dispatchers
will use distant alternate airports, or the ones they are familiar with
rather that the most cost efficient alternate based on an actual
probability of a diversion. If a
diversion is unlikely and an alternate airport is carried to satisfy
regulatory requirements, select the closest suitable alternate. As the probability of a diversion
increases, consider passenger convenience, aircraft recovery, crew duty
times, etc. when selecting an alternate airport. Today, diversions are rare occurrences
with modern aircraft equipped with autoland capabilities, adequate
airport facilities and accurate weather reporting.
- Statistics have demonstrated that on average, diversions occur one in
every 1,000 flights of which one third are due to mechanical reasons,
another third for medical reasons and the other third for weather. In the case of weather diversions, it
is often possible to anticipate the diversion during the flight-planning
phase. (Fog, thunderstorms, excessive winds, etc.)
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- Monitor fuel performance of flight crews
- An accurate Fuel MI system will permit the monitoring of the crew’s fuel
performance. While the approach should be based on the principle of
non-jeopardy, it is possible to determine the efficiency of specific
captains by monitoring a reasonable number of flights. . In practice, the variation in fuel
burn between crews will be approximately 2-3% above or below the planned
flight burn. This is particularly
evident for shorter flights because more time is spent maneuvering as
opposed to the time in cruise. Reducing the fuel burn per crew by one
percent will result in a US$40,000 saving per aircraft on the fleet
(A320 or B737). Being able to monitor fuel performance of flight crews
will entice them to be more attentive to fuel efficiency, help the
airline focus fuel training programs, monitor adherence to fuel saving
SOPs and reward the good performers, The Fuel MI should provide feedback
to individual captains on how well they manage fuel compared to the
average crew. The fuel MI system will also monitor the boarding of
additional fuel (planned or unplanned) by flight crews. Because of the
limited information available to flight crews during flight planning,
the requested additional fuel is usually not required.
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- Monitor the planning efficiency of Flight Dispatchers
- In addition to planning the most cost efficient route and minimizing
navigation charges (which in a good flight planning system should do
almost automatically), dispatchers must make significant efforts to
optimize discretionary fuel and reduce costs while at the same time
minimizing the risk of diversions. In addition to maintaining an
accurate flight planning system, the airline must provide dispatchers
with the appropriate tools including statistical information, accurate
and up-to-date weather information, and traffic information (Airport ATC
Demand Charts and graphical flight watch). The workload must be appropriate to
allow for efficient flight planning.
However, some dispatchers will systematically board unnecessary
discretionary fuel on flights resulting in significant additional costs
incompatible with proper risk management techniques. In some cases, the cost of planning
unnecessary fuel by some dispatchers will cost the airline over
US$100,000 per year before considering payload and wear on the aircraft.
In addition, the flight watch provided by dispatchers, who more closely
optimize fuel boarding, is in general of superior quality.
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- Monitor Estimated Zero Fuel Weight (EZFW) and payload optimization
- Dispatchers will tend to overestimate the Estimated Zero Fuel Weight
(EZFW) to avoid the last minute requirement for additional fuel. This results in the boarding of
unnecessary fuel, which is costly especially on longer flights where it
can affect payload. Accurate EZFWs are essential, especially for
long-range flights. A proper Fuel MI system will help determine the lost
opportunities and the cost of carrying the additional fuel. It will also facilitate the tracking
of airports from where maximum EZFW errors occur because of poor load
planning. On long-range flights,
an airline should consider a fuel top-up policy just before departure.
Re-optimizing the fuel and flight profile before departure will minimize
the boarding of excess fuel and prevent a return to the gate in case of
last minute ZFW increases over the flight plan. It would also permit the
boarding of additional fuel should higher speeds (ideally higher Cost
Indices) be required to speed up a flight due to a last minute delay.
Reassessing the alternate selection before departure might allow for the
use of a closer alternate or dropping the alternate altogether as
conditions (winds, forecasted ceiling and visibility) could have changed
significantly since the initial flight plan calculations.
- Develop efficient fuel saving procedures and monitor their effectiveness
- Fuel MI will monitor the impact of introducing new fuel management
procedures, updated navigation, communication or aircraft systems and
engines overhauls.
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- Monitor fuel cost for the various routes
- Routes have to be re-assessed continuously and their cost impact
evaluated. Fuel MI will help
monitor unwarranted route or altitude restrictions on certain flights,
identify fuel inefficient airports and support arguments for procedure
changes.
- Taxi delays and gate hold including taxi fuel
- In addition to accurately boarding the correct taxi fuel at specific
airports, closely monitoring taxi times will help analyze their impact
on on-time performance. Accurate taxi times and taxi fuel will
discourage ad hoc fuel additions by dispatchers and crews. It will also
allow the monitor block times for scheduling.
- Familiarize managers with the use the Fuel MI system
- Are the managers trained to use the Fuel MI system and is the
information distributed to the stakeholders? One reason fuel is consumed
inefficiently is the lack of reliable statistics and appreciation of its
effects on the airline’s overall budget. Often, some managers believe
there is little they can do to save fuel or that a fuel surcharge on
tickets will compensate for increase in fuel prices. In the case of
Flight Operations, while safety is the primary responsibility, lack of
upper management support, training and accountability of managers are
the primary reasons for less than optimal fuel management performance.
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- HIGH COST OF FULL THRUST TAKE-OFF
- Most engine manufacturers will agree that the maximum strain on an
engine occurs during the takeoff phase because the thermal shock is the
greatest with the highest temperatures generated. While jet engines are highly reliable,
a full thrust takeoff is when engine failures are most likely to occur.
- The most common jet engine used today is the CFM 56 (B737/A320). For
most airlines, the average time between hot section engine overhauls is
approximately 20,000 hours or 10,000 cycles (assuming an average flight
time of 2 hours). Experts agree
that if full thrust was used for every takeoff, the engine life would be
reduced by about half. Overhauling the hot section of a CFM 56 will cost
approximately $1 million. A
reduced thrust takeoff can save at least $100 per engine per takeoff in
unnecessary wear and tear.
- Full thrust takeoffs will also cause more rapid performance
deterioration and increase in specific fuel consumption. Crews should be
conscious of the cost of high thrust takeoffs and avoid them when
operationally feasible.
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- INITIAL CONSIDERATIONS
- Aircraft maintenance personnel have always been very aware of the
requirements needed to manage fuel conservation. This chapter is not
intended to bring new visions of managing aircraft maintenance – it is
simply a list of items that may act as a catalyst, and provoke thought
about possible changes in your own particular maintenance operation that
will aid in fuel conservation.
- Operators must, of course, weigh the costs of increased maintenance
against the likely benefits derived – they must define a cost/benefit
proposition, to balance savings from maintenance performance
improvements, versus cost to perform maintenance.
- A defined process of Service Bulletin (SB) or Modification evaluation
for voluntary incorporation of items can play a role in the cost/benefit
proposition affecting fleet economics. Even the incorporation of a most
desirable modification or item can add weight to the aircraft. The
overall fleet cost, for the incorporation not only of the item but the
additional fuel required to manage the increased empty weight can be
significant.
- Regular review of aircraft Empty Weight does pay dividends. Aircraft
have been known to increase by as much as 1000 pounds in a 5-year
period.
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- Any rationalized maintenance approach must be managed through the
existing approved maintenance program, the objective being to manage a
controlled process rather than executing random oversight over still
another activity.
- Existing task cards (TC) can be revised to include the actions deemed
necessary for fuel conservation activities. A key factor to using the
existing TC may be the inspection interval. As applicable, new TC’s can
be produced to meet this criteria. To the degree possible, every attempt
to utilize existing TC’s is best - but guard against overloading the TC
content.
- Once airline management has made the foregoing decisions they need to
ensure that adequate resources and personnel are provided both to manage
the aircraft downtime, and any requirements that may arise as a result
of the fuel conservation efforts.
- The maintenance training program may provide the best mechanism to
initiate fuel conservation efforts, facilitating an explanation to
personnel of the rationale behind revisions to the maintenance program.
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- POTENTIAL MAINTENANCE ACTIONS
- The following represent some of the items that may be formally
introduced into the Maintenance Program, or existing items that can be
expanded upon, to ensure the desired results. The essential target is
the elimination of drag - in all its forms.
- Inspect pneumatic manifolds and
valves for leaks. Although many manifolds are monitored by over
temperature sensing, many others are not. Even those that are monitored
may be allowed to leak yet not cause a warning indication because the
leak rate is too low. Over an entire aircraft however, this can be a
significant loss requiring additional throttle to sustain performance.
- During approach for landing
(throttled back), with the air cycle machines operative, and all
pneumatic anti-icing/de-icing selected, some aircraft exhibit the need
for additional power to provide the level of pneumatic demand, because
of the pressure loss caused by leaks. This can also change the approach
profile of the aircraft on that approach.
- Tired air cycle machines can
place a demand for additional pneumatic muscle to drive them. This
further adds to the need for additional fuel.
- Inspect for excessive autopilot
lateral input. This can cause spoiler panel operation, which induces
drag – thus increasing fuel consumption.
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- Inspect for marginal aileron
rigging that will create unnecessary drag - not to mention sloppy
performance.
- Inspect for optimum spoiler
control rigging. Spoilers are a full time control parameter - so
ensuring better than nominal rigging enhances performance by not adding
to the drag component.
- Ensure that wing leading edges
and particularly leading edge flaps, slats and slots are not dented or
damaged.
- Rough surfaces alone will
increase drag.
- Inspect the flap system rigging
for optimum position. These large surfaces are designed to manage flight
regime attitudes at controlled speeds. Out of tolerance situations will
cause excessive fuel burn.
- Inspect the rudder control system
for optimum rig.
- Inspect all the flight controls
for seal integrity. Ensure that air is directed so as to meet the intent
of the design. Where applicable inspect draft curtains for condition and
replace as required.
- Inspect all control surfaces for
maximized fit and fair positions. Ensure correct flush fasteners are
installed on all surfaces. Rough surfaces from any leaks must be
corrected.
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- Investigate all reported fuel
quantity discrepancies, ensuring that possible problems related to
contaminated probes are eliminated.
- Perform calibration checks for
the fuel tank indication system ensuring accurate quantity readings.
- Ensure regular fuel tank sumping.
Fuel tanks have experienced ice build up 4 feet in length and 18 inches
to 2 feet thick. Components in these tanks may not fail immediately but
may experience damage leading to calibration issues as well as
structural concerns.
- Inspect tanks for algae growth
and rectify as required.
- Sump drains can allow fuel seeps
or weeps. While these may be an allowable MEL dispatch criteria, over
time the fuel can affect surface finish causing roughness and a
resulting increase in drag.
- Inspect all areas of the aircraft
for both hydraulic and fuel leaks that can degrade surface finish.
Rectify leak areas and return surface finish to specification.
- Inspect pylon and other similar
drain systems. Eliminate any source of leaks and ensure surface
integrity of surfaces affected.
- Inspect wheel well doors for
optimum fit and fair conditions.
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- Ensure all door seals are
correctly installed and in airworthy condition.
- Review pilot reports for cabin
and cargo door complaints. Inspect all doors for optimum fit and fair
condition. Ensure door seals integrity. Eliminate any sources of
pressure leaks.
- Inspect the aircraft fuselage.
All panels must be installed. The fit and fair condition ensuring smooth
flow over the edges of the panel/s and mating structure must be
maintained. Any rough surfaces must be identified and returned to a
smooth condition. Any discrepancies caused by hydraulic or fuel leaks
must be corrected.
- All antennae must be installed so
as to maximize the best fit and fair considerations. This includes
attention to the detail of sealing compound applications where required.
- A major area of airflow
degradation can be the wing speed fairing/s as well as the Horizontal
Stabilizer to Vertical Stabilizer fairings. Inspect these areas to
ensure an enhanced installation eliminating sources of unnecessary drag.
- Inspect cockpit Windscreen/s to
ensure best fit and fair with the fuselage nose section structure. Any
uncured sealant that may have migrated from the sealed area must be
removed and the surface area cleaned.
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- Inspect engine and
thrust-reverser translating cowls for correctly stowed fit clearances.
The following items cause fuel burn deterioration:
- Blade rubs – HP Compressor, HP Turbine, airfoil blade erosion.
- Thermal distortion of blade parts.
- Blade leading-edge wear.
- Excessive fan rub strip wear.
- Lining loss in the HP Compressor.
- Oil or dirt contamination of LP/HP compressor.
- Loss of High Pressure Turbine (HPT) outer air seal material.
- Leaking thrust reverser seals.
- ECS leaks
- Failed – open fan air valves
- Failed – open IDG air cooler valves.
- Faulty turbine case cooling
- Failed or faulty 11th stage cooling valves.
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- On wing engine washing can
address dirt accumulation with the compressor. Leakage caused by the
bleed air system can be remedied by on wing engine bleed rigging and
additionally provide up to 2.5% Specific Fuel Consumption (SFC) benefit.
Regular on – wing engine washing can bring as much as a 1.5% SFC
improvement.
- An aircraft wash and polish
program can produce clean smooth airflows over the surfaces enhancing
fuel burn figures.
- Ensure regular Instrument
Calibration checks. Speed measuring equipment has a large impact on fuel
mileage. If speed is not accurate the airplane may be flying faster or
slower than intended. On a particular commercial transport flying at
.01M faster can increase fuel burn by 1% or more. Maintain calibration
of airspeed systems. Plugging or deforming the holes in the alternate
static port can result in erroneous instrument readings in the flight
deck. Keeping the circled area smooth and clean promotes aerodynamic
efficiency. Maintenance operations must ensure the use of proper tooling
to block the static ports. Check the Illustrated Tool and Equipment List
(ITEL) for the applicable aircraft model.
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- ESTIMATED FUEL SAVINGS
- Here is an example of the estimated fuel penalty in liters per year, per
aircraft, for a 5 millimetre surface mismatch.
- 5mm Surface Mismatch Litres per year per aircraft
- Passenger Front Door 9,000
- Nose Landing Gear Door 8,400
- Cargo Door - Forward 8,800
- Here is an example of the estimated fuel penalty in liters per year, per
aircraft, per each 5 centimetres of missing door seals.
- 5cm Missing Seals Litres per year per aircraft
- Sides Top/Bottom
- Passenger Front Door 1,500 800
- Cargo Door 1,500 800
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- Here is an example of the estimated fuel penalty, in liters per year,
per aircraft, for a control surface mis-rigging of 10 millimetres.
- 10mm Mis-Rigging Litres per year per aircraft
- Slat 28,000
- Flap 10,000
- Spoiler 32,000
- Aileron 10,000
- Rudder 13,000
- Here are some examples of the estimated penalty in litres per aircraft
per year for single dents or blisters.
- Area Surface Area Damaged – 5mm Depth Litres per year per aircraft
- Fuselage 20 Square CM 70
- 80 Square CM 270
- Wing 20 Square CM 85
- 80 Square CM 370
- Tail 20 Square CM 45
- 80 Square CM 90
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- Here are some examples of estimated fuel penalty in litres per year, per
aircraft for 0.3 mm of skin roughness over 1 square meter.
- Skin Roughness over 1m2 on: Litres per year per aircraft
- Fuselage 3,300
- Wing Skin Upper 12,000
- Wing Skin Lower 6,000
- Tail 5,800
- Here are some examples of estimated fuel penalty in litres for parts
missing.
- Type of Deterioration Litres per year per aircraft
- Absence of seal on movable surface Per meter of missing seal
- Slats (span wise seal) 14,000
- Flaps & Ailerons (chord-wise seal) 9,500
- Elevator 6,300
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- Type of Deterioration: Litres per year per aircraft
- Engine Cowl: One pressure relief door missing 134,000
- Cargo Door: Lock cover plate missing 1,000
- Fin/Fuselage junction (fairing & seal missing) 39,500
- Elevator bearing access cover missing 19,000
- The double outcome of this drag component is not only the added cost of
fuel to overcome it but also the lost payload. On a typical commercial
transport it is conceivable, that in order to offset a 1% increase in
drag, a reduction in Zero Fuel Weight (ZFW) could be 260 pounds/118
kilograms, in order to maintain a constant takeoff weight.
- (Note that the reductions vary as actual values vary with distance
flown. Also the above figure varies up or down depending on the actual
aircraft in question).
- Considering the example provided above, a 1% drag in terms of gallons
per year could result in approximately 25,000 gallons. Any one item on
this list may of itself bring miniscule benefit. However, in combination
the savings can be substantial per aircraft. Exponentially applying
these figures to an operator’s fleet brings large returns.
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- Objectives of Flight Planning
- It is generally recognized that being able to get the maximum payload
from origin to destination - whilst achieving the highest degree of
safety and efficiency - is the main objective of Flight Planning. The Flight Dispatcher and Captain
should strive to flight plan to arrive with the correct amount of fuel;
no more than or less than the fuel required to safely and efficiently
operate the flight.
- Flight Planning Considerations
- a) Safety: Consideration of many
factors goes into the Flight Planning process. These include:
- •route selection;
- •alternate selection;
- •arrival and departure runways;
- •enroute alternates if required; MEL;
- •runway performance limitations; and
- •origin, En-route, destination and alternate weather.
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- b) Efficiency: No longer is it
sufficient just to be safe. It is vital that the Flight Planning process
takes into consideration the full range of Cost Index planning
capabilities with the appropriate vertical and lateral optimization. The
vertical and lateral optimization should vary with the planned Cost
Index as the winds and temperatures will vary and therefore the final
vertical and lateral profile will be different. The vertical
optimization should look both up and down as winds and temperature vary
greatly at different altitudes.
- c) Overflight Fees: In recent
years sophisticated Flight Planning systems have been able to select
routes that are optimized to produce a Minimum Cost operation taking
overflight fees into consideration. In some parts of the world just a
minor deviation in the route avoiding a particular country or FIR may
produce significant savings in overflight fees.
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- ROUTE SELECTION AND PLANNING
- There are many factors that go into route selection. The choice of route
selected by the Flight Dispatcher plays a major role in the
profitability of the flight. For example:
- a) Short Range Flights less than
3 hours: With many short-range flights, the options to save fuel are
limited - but with sometimes between 30-40 flights per day between some
city pairs the savings quickly accumulate just by saving one minute per
flight.
- In high-density airspace, routes will often be “fixed” by ATC - both in
terms of route and altitude. However, occasionally there maybe several
“fixed” routes available between any city pair. As a rule, always
analyze all available options to ensure maximum fuel efficiency. Take
into consideration the navigation capabilities of the aircraft, because
in some cases, routes for a city pair may be designated for FMS aircraft
only.
- b) Long Range Flights: Today’s Flight Planning systems should
be able to optimize for Minimum Distance, Minimum Fuel, Minimum Time or
Minimum Cost. It is possible - or
sometimes desirable - to fly minimum distance and minimum time. This
will often result in a lower flight level therefore increasing the fuel
burn.
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- In most cases, however, the choice will come down to a selection between
minimum fuel and minimum cost. Where possible plan for enroute step
climbs; however when unable to plan the most optimum altitude for fuel
economy, it is usually better to opt for the best lateral profile and
accept a slightly less than optimal altitude.
- c) Runway Selection: For greater
accuracy, the planned take-off runway, the departure and arrival
procedures and landing runway should all be included in the flight
planned route.
- Alternate Selection
- All alternates shown on the Operational Flight Plan must be in
compliance with applicable regulatory and company policies. The
following guidelines should be considered during the alternate selection
process.
- Diversions for weather very rarely occur and when they do the aircraft
often does not proceed to the flight planned alternate. The cost of
carrying the fuel for an alternate is huge; an occasional diversion is
often cheaper than carrying extra fuel to prevent a diversion.
- Despite the best efforts of both the Flight Dispatcher and Captain,
diverts will happen. The decision to divert is most often a
demonstration of good judgment. Even if the flight was carefully
planned, using policy, and all appropriate information, it is
conceivable that conditions may change that will ultimately lead to a
diversion. This should, therefore, not be considered as a deficiency.
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- a. Take-off Alternates. It is not
normally necessary to add fuel for a take off alternate;
- b. Destination Alternates.
Destination Alternates are for planning purposes only and in order to
minimize the fuel uplift a careful evaluation of the risk of a diversion
is necessary.
- •If there is a low risk of a diversion then plan the closest legal
alternate or where regulations permit plan “ No alternate IFR”.
- •The risk of not arriving at the airport, and the risk of holding in the
terminal area should be separated. Just because the destination weather
forecast is poor does not necessarily mean there is a high risk of a
diversion. If the airport had multiple runways with Cat II or Cat III
approach aids available then the chances of a diversion are minimal.
However there may be delays in terminal area if the weather has slowed
down the approaches - therefore the right amount of additional fuel
should be added accordingly. It should not be necessary to have a long
alternate AND additional fuel for the terminal area.
- For some operational and commercial reasons it may be necessary to
flight plan with two alternates. Before planning with two alternates
give careful consideration as to why? You may be carrying unnecessary
fuel and by having two alternates you are increasing the workload of
both the Flight Crew and Flight Dispatcher, as both alternates need to
be monitored.
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- Statistical Discretionary Fuels
- Statistical and Discretionary fuels are those carried over and above
Contingency Fuels, which are usually governed by regulation.
- In the past, Contingency Fuels were often fixed at either 5% or 10% of
the burn-off. However, fuel requirements set by the States are often
many years out of date and overly conservative and do not take into
consideration the accuracy of Flight Planning today. Many airlines have
engaged their State regulator and obtained reduced Contingency Fuels
based on reliable fuel monitoring programs and the provision of
statistics demonstrating that safe flight operations can be maintained.
- Statistical Fuels. Many airlines have now developed a Fuel Management
Database for use by Flight Dispatchers and Pilots. It is normally a
historical record of actual fuel information such as:
- burn off;
- contingency fuel used versus
contingency fuel boarded;
- additional fuel used versus
additional fuel boarded.
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- Accurate additional fuel figure increments should be developed.
Additional fuels should only be carried in increments of one minute. Why
add 5 minutes of fuel if statistics show that 2 minutes is sufficient?
- Additional fuels should only be
carried for known or forecast operational reasons.
- Remember a lighter aircraft is a
safer aircraft. Amongst other things it provides:
- greater terrain clearance on take-off;
- ability to climb quicker;
- higher cruise altitude;
- better stall recovery and lower stall speed;
- lower approach speed;
- reduced landing distance and reduced tire and brake wear.
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- Here are some reasons NOT to carry additional fuel:
- This flight held for 10 minutes last week;
- The Captain always likes additional fuel;
- I don’t trust the forecast, evaluate whether there is a real risk of a
diversion; and
- The payload might increase.
- Every time you do not carry additional fuel you are contributing to the
profitability of the company, increased payload opportunities and better
aircraft performance.
- Fuel Tankering
- A fuel tankering program should be an integral part of the flight
planning system. It is important that the daily fuel price fluctuations
are taken into consideration and close liaison with the fuel purchasing
department is essential. For ecological reasons, consider tankering only
when there is a definite commercial benefit for the airline. Tankering
is normally limited to shorter flights, or for operational reasons.
Consider the full cost of carrying the additional fuel including wear
and tear on the aircraft.
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- When planning to tanker fuel, the maximum limitations of the aircraft
should not be approached. This includes maximum performance take off and
landing weights as well as the maximum tank capacity of the aircraft.
Sufficient margins should be left to allow any last minute additional
payload to be carried and so as to not adversely impact the next flight
leg.
- Tankering fuel is not recommended for the following:
- Flights landing at airports that have reported poor braking action - or
weather forecasts predict conditions which may result in poor braking
action;
- Flights landing at airports that have very short runways;
- Flights landing at "hot/high" airports where single engine
go-around limits may be approached;
- Care should be taken when tankering fuel into areas with low
temperatures and high relative humidity and precipitation; and
- Long-haul overseas flights where the cost to carry become excessive and
the associated aircraft performance becomes limiting e.g., unable to
step climb.
- Re-Dispatch Technique
- This is a procedure where the flight is not planned all the way to the
destination, but is instead planned to an airport short of the
destination. For example, a flight planned from Frankfurt to Chicago
could be planned at the outset to Toronto with an alternate of Detroit.
Once airborne the flight will be able to re-clear to its final
destination using some of the contingency fuel as burn fuel.
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- There is usually a re-clearance point where the aircraft must have
sufficient fuel onboard to reach its final destination, with an
alternate if necessary, and the appropriate amount of contingency fuel.
- The procedure can offer significant potential fuel savings, as ATC
clears the flight to destination from the onset, and all the necessary
fuel requirements are clearly established before departure.
- With accurate flight planning systems, most of the flight planned
contingency fuels remain unused, and the re-dispatched technique will
bring large benefits in both fuel savings and payload optimization -
especially on long-range flights.
- Depending on an airline’s fuel policy, between 5 - 10% of contingency
fuel is normally boarded. Since
flight conditions can change during flight, and sometimes the alternate
airport is no longer required for the arrival, re-dispatching the flight
can prevent an en-route stop while carrying maximum payload.
- It is recommended that prior to commencing any Re-Dispatch technique for
flight planning that the State regulator is consulted to ascertain if
the procedure is permitted.
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- Flight Dispatcher – Pilot Relationship
- Whilst the Flight Crew has the final responsibility for fuel management
in flight, it is the Flight Dispatcher that takes the decisions to board
the fuel on the aircraft. Usually by the time the flight crew gets to
the aircraft it is too late to take any fuel off, so it is essential the
Pilot and Dispatcher work as an effective team to discuss the best and
most fuel efficient way to complete the flight.
- Unfortunately, access to the Flight Deck in many parts of the world is
no longer as simple as it once was - even for qualified airline
personnel. So it is more difficult for Pilots and Dispatchers to get to
know each other.
- However, there are other ways. When introducing new fuel policies or
procedures, have the Pilots and Dispatchers take the same training
course. That way there can be an effective exchange of ideas and
experiences. Encourage Pilots to visit the Flight Dispatch or Operations
center during training sessions. Pilots are often unaware of the
sophisticated tools that Dispatchers have at their disposal.
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- Flight Watch
- Some airlines have qualified Flight Dispatch personnel where Flight
Watch is an integral part of the airline’s operational control process.
Certified Flight Dispatchers share responsibility for flight watch with
the Pilot-in-Command, and share all pertinent and related flight
information and any proposed changes to the Flight Plan.
- This process can greatly enhance flight safety, and will ultimately
produce the safest and most cost effective operation. The Flight Crew
cannot adequately analyze the significant amount of data and factors
involved in planning a flight without experienced knowledgeable
assistance from the ground.
- Once a flight is airborne, the Flight Dispatcher can advise the Flight
Crew of many issues, all of which will enable the crew to better manage
the fuel efficiency of the flight. These include:
- Are there delays at the destination? In which case slow down and save
fuel;
- If the flight is running late, can the aircraft speed up to avoid
missed connections? Burning a little more fuel is usually preferable to
having passengers miss connecting flights
- The Re-dispatch technique is best practiced with qualified Flight
Dispatchers able to provide the flight crew with the latest information
to re-clear them to their destination.
- Contingency fuel may be available to provide either a longer alternate
or provide holding fuel at the destination
- Additional fuels may be available other than the reason for which they
were originally carried.
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- OVERVIEW
- Today's economic climate is very hard on Air Transport Operators and
belt tightening is the order of the day. All areas of operation are
being investigated with the hope of finding means to economize. The
recent dramatic rise in the price of fuel oil means that aviation fuel
costs now account for over 20% of the total operating costs for an
airline – and in some cases much more.
- In order to reduce fuel consumption, most Air Transport Operators are
making changes to their operating procedures and are attempting to
improve flight planning, management and operating techniques. Some of
the changes alter the operating characteristics of aircraft and it is
here that Air Traffic Control becomes involved.
- The previous chapters describe many of the fuel saving measures that can
be taken by Air Transport Operators. Air traffic controllers, and air
navigation service provider managers, are encouraged to read these
chapters, to better understand the actions being taken by operators, and
to use this knowledge to work with operators in their fuel conservation
efforts.
- This chapter looks at how good strategic Air Traffic Planning and
Management practices – and tactical Air Traffic Control practices – can
influence and complement operator fuel management practices.
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- There is no intent to change rules or existing ATC procedures – and the
primary focus must remain on safety; however where safety is not
impacted, every effort should be made to facilitate the actions being
taken by operators.
- Take the following example.
- There are around 30 million scheduled air transport operations around
the globe annually. The average flight time is about 1 hour and 37
minutes. The average operating cost per minute for an air transport
operator is USD$100. reducing flight time by just 1% - that is, by just
1 minute – could reduce airline operating costs by USD$3,000,000,000.00!
- It is recognized that with high-density traffic any appreciable changes
to the day-to-day operation are limited; however there are areas –
particularly in lower density environments, or in times of light traffic
- where opportunities for greater flexibility do exist, which could be
translated into tremendous savings for Air Transport Operators.
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- FUEL IS BURNED TO CARRY FUEL
- On average, a modern jet aircraft burns about 3-4% of the weight of
additional fuel carried per hour of flight. So, on a 7-hour
trans-Atlantic crossing, if an aircraft boards an extra 5000kg of fuel,
it will burn around 1300kg of that fuel – just to carry it! On a 14-hour
trans-Pacific flight, it will burn more than half of that fuel – just to
carry it.
- This is a basic - but very costly - fact. For this reason, pilots are
encouraged to carry only the minimum load of fuel that is essential to
the safety of the flight. Determination of the amount of fuel to be
carried is based on a number of factors.
- Increasingly, dispatchers and airline operational control are using
sophisticated programs to determine historical trends in weather
diversions at destination, average taxi times, average terminal area
manoeuvring and so on to calculate the amount of fuel that should be
carried.
- It should be remembered that the carriage of additional fuel has a
two-edged economic effect. Operators incur a cost to carry the fuel –
and lose the opportunity to carry the equivalent weight in revenue
generating passengers or cargo.
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- STRATEGIC MANAGEMENT
- In many cases the design of airspace, air routes, and ATC procedures is
based on “lowest common denominator” principles – that is, they are
designed around the “lack of equipage or capability”, rather than
catering for the evolving fleet equipage and capability in particular
areas. Modern aircraft have the capability to fly direct routes, with
great accuracy, and can meet ATC requirements with high levels of
confidence, without the need for ATC to apply speed or track
interventions.
- Many terminal area procedures, and many enroute route structures are
built around ground based navigation infrastructure that is no longer
required. Airspace planners should take every opportunity to review
routes, SIDs and STARs and to work with local airline representatives to
ensure that established procedures and routes more closely match the
capabilities of the fleets.
- There is a need for ATC managers to constantly review procedures and
eliminate inefficiencies in the system.
Just because “we have always done it this way - so why change it”
is just not good enough. There is a constant need to look at the new
generation airplanes with sophisticated navigation systems and
capitalize on their capabilities.
Some airplanes can give you a required time on arrival (RTA) very
precisely to metering points.
- Most air transport operators recognize the critical importance of fuel
costs by assigning a role of Fuel Manager to some the most senior
operational staff in their organizations. The role of that person is to
look for every opportunity to conserve fuel.
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- Fuel and environment management is a partnership arrangement, and better
awareness of the operating paradigms and limitations of each of the ATM
partners can add significantly to overall system efficiency. The
appointment of a Fuel and Environment Champion within a Service Provider
organization would enable all fuel and environment efficiency actions to
be focused and harmonized with airline actions. Indeed, just as for
pilots, we recommend that fuel efficiency figures prominently among the
key performance indicators of air traffic controllers.
- Possible Fuel Champion Accountabilities
- Within the overall constraint that no action will compromise safety, the
general role of a Fuel and Environment Champion would include:
- Develop programs which will minimize fuel consumption, operational
costs and environmental impact for airspace users;
- Support ATS Planning offices in the design and implementation of fuel
efficient routes and terminal area procedures;
- Work with ATS training institutions to ensure awareness of fuel
conservation techniques are incorporated into basic ATS training;
- Liaise with the fuel managers of locally based airline or other
aviation organisations to understand fuel and environmental issues of
local importance;
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- Monitor global best demonstrated practices in fuel management
throughout the aviation industry;
- Provide fuel and environment conservation training to all ATS staff –
both operational and management, including regular briefings from local
airline fuel management staff;
- Liaise with local air operators, and where there is predominantly
through traffic, with the local airline agents, to support the
development of efficient ATC procedures and training programs for
controllers and ATC managers including the environmental impact of
inefficient ATC practices;
- Continuously sensitize ATS staff and management about the cost of fuel
– both in dollar terms, and environmental impact - and its impact on
the operating efficiency of airspace users;
- Encourage the establishment of familiarization flight for ATC
controllers and visits to ATC centers by pilots;
- Encourage the establishment of a program to visit airline dispatch and
flight planning offices, to better understand the factors affecting
scheduling and flight mission management.
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- AT THE GATE
- Aircraft standing on the apron or at a gate prior to flight need power
for a range of functions, including air conditioning in the cabin,
electrical power to aircraft systems, and so on. An aircraft at the gate
could be powered by one of three sources – a ground power unit, an
aircraft auxiliary power unit [APU], or the aircraft’s main engine.
Using an Airbus A320 as an example, the relative [ground run] costs are:
- Power From: Operating Cost per Minute
- Ground Power Unit USD$0.30
- Auxiliary Power Unit USD$3.00
- Aircraft Engine USD$25.00
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- In November 2004, average jet-fuel cost was USD$1.70 per gallon. This
may not seem like a large sum – however one airline has estimated that
its fleet could save $250,000 per year just by delaying APU start by one
minute.
- It’s important, then, for air traffic control to notify aircraft
operators as soon as possible if there is likely to be a delay in start
or pushback, so that the cheapest power source can be maintained for as
long as possible.
- If delays are anticipated, the sooner the pilot knows the more
economical it can be!
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- TAXIING AND DEPARTURE
- The price of taxiing, in fuel alone, can vary from $25.00 per minute for
an Airbus A320, to $50.00 per minute for a B747. Every delay, every
extended routing, every stop-and-start, costs somebody money. One
airline has estimated that one-minute less time spent taxiing on every
flight in 2004 would have saved them $1,654,000. Even 10 seconds would
have been a $275,666 saving, for one airline.
- Many operators are introducing new procedures to economize while
taxiing. Fuel has become more expensive than brake-wear. Unnecessary
engines will be shut down whilst taxiing.
- An engine out taxi – particularly at airports with long taxi distances –
can save many thousands of dollars when aggregated across a fleet over a
year – BUT the advantage is lost, of course, if the aircraft must stop
and then spool up the active engine[s] to start rolling again. If a taxi
delay is anticipated for some reason, advising the pilot of the
situation might encourage a gate hold or taxi with one or in some cases
2 engines out taxi. The problem
is that often pilots are not able to see a departure line up and only
see it as they approach the runway.
- As a matter of good technique, the practice should be to try to keep
aircraft on taxiways moving at all times, and if there is a choice
between an aircraft and a vehicle – try to let the vehicles wait.
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- Time spent taxiing in relation to the runway used for departure is being
analyzed as well. In Fuel Terms, every minute of additional flight time
in the wrong direction after departure equals from 3 to 7 minutes of
taxi time, depending on the number of operating engines. A B767, for
example, could afford up to 12 minutes taxi time on 2 engines in order
to trade off a runway aimed the wrong way and use its reciprocal. Most
airlines will taxi the extra distance to get a runway that is even 30°
closer to the flight path.
- Again the good technique question should be “could an alternate runway
be safely approved?”
- Both takeoff and landing will be affected by the operators’ energy
awareness. Aircraft will be taking off with reduced thrust and lower
flap settings, and may be requesting intersection takeoffs in order to
save taxi time. Rolling takeoffs are more fuel-efficient.
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- CLIMB
- Airlines say that when departing on a heading away from the destination
airport their climb speed will be decided by the following:
- If departure control needs DISTANCE before a turn, the aircraft will
complete the noise abatement procedure and accelerate to optimum clean
speed to 3000 ft AGL;
- If altitude is required prior to turning they will maintain minimum
clean speed (or max pitch) to that altitude. The aircraft will trade
speed for altitude. In other
words, it will keep the take off flap configuration so as to reach the
altitude with minimum distance where a turn to the on-course can be
initiated as soon as possible.
Then at low speed, the rate of turn is very high and the
distance away from the intended direction is minimized.
- When cleared to turn on a normal climb-out they will use the maximum
permis¬sible bank and minimum clean speed until within about 90° of the
on-course; then commence acceleration to normal climb speed.
- Where it is practical to do so – and consistent with safety –
controllers should consider canceling Standard Instrument Departures
[SIDs] as soon as possible. They should also initiate on-course climbs
at pilot discretion.
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- CRUISE
- An A340 flying 4,000 feet below its optimum cruise altitude will use 400
kg of extra fuel per hour. At today’s prices, that works out to
USD$176.00 or almost one short-sector return airfare.
- Every aircraft has an optimum altitude at which it can operate. Optimum
altitude, simply stated – and in the absence of other economic factors
[refer section 9 – Mission Management] - is the altitude at which
aircraft can fly the most ground miles per 1000kg of fuel.
- This altitude is determined individually using as many of a long list of
variables as are available to the pilot. The primary factors considered
are aircraft weight (which changes as the aircraft burns fuel), winds at
the various altitudes, temperature, and length of the flight stage. Many
airlines and charter companies employ the services of central
computerized agencies to provide the most up-to-date information
possible.
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- When the flight segment is too short to permit the optimum altitude, the
most fuel-efficient profile is a climb until intercept of the descent
profile.
- It is an unfortunate - although often unavoidable - fact that the
efforts made to maximize fuel efficiency in cruise can very quickly be
negated by the inability of ATC to approve a request.
- It is important that ATC maintain a constant awareness of the impact of
assigned altitudes on fuel efficiency.
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- SPEED AND VECTORING
- Most airlines operate using a cost index management methodology to
determine an optimum cruising speed or Mach Number, in order to either
conserve fuel, or to achieve a better “business outcome”. So, when an operator requests a
certain preferred Mach number, it is likely that it has been carefully
calculated to achieve a specific economic outcome.
- The cost penalty of flying at 0.01 Mach high or low could be 5½ cents
per mile (at 4.5 million miles per month for one operator this would
equal $3,000,000 per year!). With Cost Index optimizing the speed, in
most cases changes in the aircraft speed can be mitigated though the
en-route phase of flight; however, it becomes a more significant problem
as the flight approaches destination.
- Controllers should also be aware of the meteorological conditions
prevailing in their sector of responsibility – and the likely effect in
terms of aircraft requested speeds or levels. In order to achieve the
desired business outcome, an operator may reduce speed with a tail wind,
or increase speed into a headwind.
- When a speed increase/reduction is required for control purposes try to
co-ordinate with adjacent sector/units so as to maintain uniformity
through out the flight segment.
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- Modern aircraft Flight Management Systems [FMS] are able to calculate
the effects of a proposed change quite quickly. If there is time,
controllers should consider asking a pilot for options. For example,
many aircraft have a “Required Time of Arrival” [RTA] function, and over
an appropriate route segment can program the FMS so that an aircraft
reaches a point with a high degree of accuracy. ATC will achieve their
desired outcome – and the pilot and FMS will have determined the most
economic way of achieving that outcome.
- Where a speed restriction or requirement is imposed, it should be
canceled as soon as it is no longer required.
- It is an inevitable part of ATC that in radar areas, aircraft will be
vectored. Where there is a choice, however, and provided the route
segment is sufficiently long, an aircraft will generally prefer speed
control over vectoring. Better still – use the RTA function described
earlier Whilst a vector of just 8 miles may seem insignificant, in
cruise it amounts to a minute, and if repeated just once per day, it can
cost over USD$36,500 per aircraft per year.
- If there is a message that comes in clear from all airlines, it is that
— VECTORING FOR SPACING USES TOO MUCH FUEL! They all prefer to be slowed
down for separation rather than sent on wide and fast routes. Speed
control is far more efficient than vectors from a fuel economy point of
view. In fact, although there is a small penalty for increasing speed
(which ATC seldom require) there is a considerable saving in decreasing
speed in most cases.
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- It is also important to let pilots know what you intend to do – BEFORE
you do it. This is particularly important in a terminal area. If you
have an idea of the track miles to run – advise the pilot. This will
allow them to adjust their profile. If you know the position in a
sequence – let the pilot know. They may be able to monitor the traffic
and adjust their profile.
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- DIRECT ROUTING
- The use of more direct routes, whenever possible, may mean only 10 miles
per flight. However, when that 10 miles is multiplied by, say, 10
flights per day, and the number of flights per day times 365, the saving
is USD$4,000,000 per aircraft per year!
- However – direct routing may not always be in an operator’s best
interest! In some cases, assigning a direct route to an aircraft can
actually take that aircraft into adverse weather conditions that will
negate any track mile savings. It may also invalidate already programmed
arrival procedures. It is a matter of good technique – in particular
where the direct routing is over a relatively long distance – to offer
the direct routing to the pilot rather than simply clearing the
aircraft. There may be occasions where a pilot is reluctant to question
a controller clearance.
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- DESCENT
- A properly planned and executed descent provides the greatest
oppor¬tunity to save fuel. The ideal profile is an unrestricted descent
from cruise altitude, at a planned distance, without the use of thrust
or drag devices until on final approach.
- On many aircraft start down points are pre-calculated by on-board
computers with the following factors taken into consideration:
- •Wind corrections
- •Airport altitude
- •Air miles to go (including anticipated vectors)
- •Runway in use
- •Landing weight
- If descent is interrupted and the aircraft forced to level off at an
intermediate altitude, most pilots will (allow the aircraft to) slow
down as much as possible while level, then trade surplus height to
regain descent speed.
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- Late descent increases fuel consumption as more time is spent with
cruise power and the extra height energy must be dissipated with drag.
When possible ATC should give descent clearance when requested by the
pilot, or better yet, give such clearance early and advise the pilot to
commence descent at his discretion.
- Controllers should be aware that pilots may use "IDLE THRUST"
technique if required to level off for a portion of descent. This will
result in a reduction of ground speed until such time as the aircraft
begins further descent. This may negate the control effect they were
trying to achieve.
- Significant increases of fuel burn are experienced when descent is
commenced either too early or too late. (The penalties are even greater
if descent is initiated too late). If descent is started just ten miles
early, it can incur a penalty of over 200kg of fuel to a B747.
- ATC should coordinate descent early - not when the aircraft asks for
descent. Better still, controllers should ask pilots when they want to
start down.
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- HOLDING
- Holding, although expensive, is sometimes inevitable. In order to reduce
the fuel cost as much as possible, consider the following:
- When advised that a hold is expected, most aircraft will wish to slow
down in order to absorb as much time enroute as possible. Some pilots
refer to this procedure as a "linear hold".
- Most aircraft will want to stay at altitude as long as possible.
Holding low is very fuel inefficient.
- If holding is anticipated, let the pilot know early.
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- APPROACH AND LANDING
- The most fuel-efficient aircraft in the approach and landing phase is
the NASA space shuttle. It uses no fuel but a carefully calculated
system of energy management, which results in the elimination of inertia
and altitude simultaneously.
- It is obvious that aircraft do not operate in the sterile environment
that the space shuttle does; however, when the same principles are
applied to arriving aircraft the result is a dramatic increase in energy
conservation. If the energy that is already contained in the inertia of
the aircraft is used (altitude and airspeed) then very little engine
power will be required.
- To achieve this airlines will:
- •request runways which reduce flying time;
- •adjust speed whenever possible rather than flying extra miles;
- •keep the aircraft clean as long as possible in order to reduce
unnecessary drag;
- •fly visual approaches whenever able;
- •carry out reduced flap landings whenever possible
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- Be aware that “idle reverse thrust” is less fuel expensive than “full
reverse thrust”. Idle Reverse use is being recommended where
operationally feasible. However, because of the extra rollout, aircraft
may not be able to clear the runway at their "usual" cutoff.
- That said, many modern aircraft using auto braking will stop at the same
point regardless of the level of reverse thrust used. Auto braking gives a selected rate of
deceleration, which under normal conditions will slow the aircraft at
the selected rate. Unless there are slippery conditions where the
anti-skid system would release the brakes to prevent wheel locks, the
stopping point should be the same.
Most operators recommend the use of idle reverse to neutralize
the engine forward thrust on landing.
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- WHAT CAN AIR TRAFFIC CONTROLLERS DO?
- Whenever safely possible, ATC should:
- “Keep'm Rolling” on the ground — let the vehicle wait
- Accommodate aircraft taxiing with some engines shut down
- Approve alternate runways
- Approve take-off in the direction of flight
- Provide clearances in time to accommodate rolling Take-Offs
- Cancel the SID’s as soon as practicable
- Co-ordinate direct routes
- Try to approve optimum altitudes
- Co-ordinate and issue descent clearance early
- If a hold is anticipated let them know early
- Use speed control (slow them down) rather than Vectors
- If two aircraft are tied, try to give preference to “the gas guzzler”.
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- Internal Action Items and Checklist
- THE SCHEDULE
- Is your operational schedule
built for maximum fuel efficiency, optimized speeds, and best Cost Index
values (Time cost versus fuel cost)?
- How often is your flight schedule
(flight times and Cost Index) adjusted to cater for fuel prices changes?
- Are your Cost Index values
adjusted for specific routes?
- Is your schedule adjusted for
seasons, time of day, and day of the week?
- Are you using the right aircraft
on the right route to minimize fuel consumption per passenger?
- Do you have a process to perform
aircraft swaps based on last minute load changes?
- Does your schedule minimize
aircraft positioning or ferry flights?
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- Do you have an early departure policy for over scheduled flights that
would permit the use of a lower Cost Index and still arrive on time?
- Is Cost Index flight planning and
flying available for your non-FMS aircraft types or other aircraft
types?
- Are high over flight charges
causing inefficient fuel planning?
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- MISSION PLANNING AND COST OPTIMIZATION
- Are you properly and effectively
managing the curfews, early morning holds, and so on?
- Are you attempting to slow down
early arriving flights to prevent gate-holds, ramp congestion and reduce
fuel consumption?
- Do you track gate-holds to
prevent gate holding short of the gate with engines running, and
therefore minimize fuel burn on the ground?
- Are some routes unnecessarily
[flight plan] altitude capped?
- Are your dispatchers adding fuel
for ad-hoc reasons? (such as night shift, workload, shift changes,
specific captains, to avoid calls from the crews, preferences, seat of
the pants feelings, habits, don’t trust the forecaster, etc)
- Do you have a well-defined and
clear Fuel Policy? (Usage of
available fuels with purpose for each type of additional fuel, Captain’s
authority to manage the fuel, efficient fuel reserves, well define
categories of discretionary fuels, minimum FODs, fully integrated in the
flight planning system, specific guidelines for alternate selection,
crew fuel additives, taking advantage of modern aircraft and airport
facilities, holding fuel guidelines, unusable fuels, use of minimum
reserve fuel, use of alternate, taxi fuel calculations, cost to carry
additional fuel information, etc.)
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- Do you have a recommended arrival fuel for each airport over which
dispatchers and pilots should look for opportunities?
- Are additional fuels itemized on
the flight plan? (ATC delays,
Captain’s request, MEL, Weather enroute, ETOPS, etc.)
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- GROUND TRAINING ON AIRCRAFT PERFORMANCE AND EFFICIENCY
- Are all of your pilots up to the same standard regarding aerodynamics
and fuel-efficient flying? Do you train pilots and dispatchers on the
fuel policy?
- Are the crews trained on efficient FMS programming to cross check the
flight plan fuel and accurately manage the fuel in-flight?
- Are all the training captains, line introduction pilots, check pilots,
simulator instructors fully conversant with the latest fuel saving
techniques. Do they support an
efficient fuel management program?
- Are fuel-saving techniques introduced at initial training, or conversion
training? Are these techniques reviewed at the annual training sessions?
- Do all of your chief pilots and upper management support efficient fuel
management?
- Do you publish the potential savings associated with reducing flight
time by one minute, saving 100 kg of fuel, the cost to carry 100 kg
extra on each flight, fuel prices, etc?
- Do you have statistics on diversions?
(Flight diversions today are around one in 1,000 flights and are
about 33% for mechanical, 33% for medical reasons, THE LAST 1/3 for
weather reasons. Most diversions are to an airport other than the
planned alternate.)
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141
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- ALTERNATE SELECTION PROCESS
- Is your alternate selection
process optimized to minimize cost and according to the risk level?
- Do you take maximum advantage of
the aircraft technological capabilities and destination approach
facilities during flight planning?
- Is your flight-planning system
using the lowest possible fuel burn for alternate fuel requirement
calculations?
- STATISTICAL FUEL BOARDING AND FUEL CONTINGENCIES
- Do you board additional fuel
according to accurate statistics, and are your airport demand charts
properly optimized? Do you assign the most fuel economical aircraft to
longer routes?
- Do you have validated data to
support such a system?
- Is discretionary fuel added for
foreseeable delays, or for comfort? (Fuel should be added when there is
a strong possibility of it being used)
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- RECLEARANCE AND REDISPATCH
- Is the re-clearance or re-dispatch technique used for longer-range
flight to minimize fuel burn and optimize payload?
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143
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- TANKERING
- Do you have a tankering program
in place, and is it well optimized?
- Is your flight planning system
properly computing tankering costs?
- Is the “cost-to-carry” computed
by your flight planning system?
- Do you use strategic tankering
and are the costs well understood?
- How often do you update fuel
prices in your flight planning system?
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144
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- FUEL MANAGEMENT INFORMATION [MI] DATABASE
- Is your Fuel MI Database accurate and detailed, and is it comparing
actual to flight planning data?
- Do you have a full time Fuel Program Manager or Fuel Database Manager?
Is that person operational i.e., a pilot or dispatcher?
- Do you use the information properly and distribute it to appropriate
stakeholders?
- Do your stakeholders understand and use the Fuel MI data to improve fuel
efficiency?
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145
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- FUEL EFFICIENCY TRACKING AND CONTROL USING THE FUEL MI DATABASE
- Do you conduct post-flight
analysis of arrival fuel and time performance?
- Do you have a fuel-efficiency
monitoring program for pilots?
- Are fuel performance statistics
and feedback made available to your flight crews?
- Do you have a fuel-performance
tracking program for dispatchers?
- Do you maintain accurate fuel
burn data for each specific aircraft?
- Do you have a system or program
to monitor fuel inefficient aircraft and/or engines?
- Do you have a maintenance program
to minimize burn for fuel inefficient aircraft e.g., engine wash,
surface condition and cleanliness, aircraft paint?
- Is the individual aircraft fuel
performance regularly updated in your flight planning system?
- Do you regularly monitor and
analyze excessive “Fuel over Destination (FOD)”?
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146
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- Do you monitor over-fueling by
re-fuelers or flight crews?
- Do you monitor and analyze the
costs of adding high amounts of discretionary fuel?
- Do you monitor the cost of using
unnecessarily distant alternates?
- Do you have a no-alternate IFR
policy and is it properly used?
- Are your Chief Pilots and other
stakeholders accountable for a fuel-efficient operation?
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147
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- WEIGHT MANAGEMENT
- Do you have a program to manage aircraft weight? (such as minimizing the
carriage of unnecessary water, magazines and newspaper, toilets
servicing, blankets, cargo containers, crew baggage, carry on baggage,
unnecessary galley supplies, ovens, garbage, etc)
- Do you have a center of gravity management system for passengers and
cargo (C of G)?
- Are your estimated zero fuel weights accurate (EZFW)?
- Do you have a last minute fuel top-up policy especially for long-range
flights to avoid carriage of unnecessary fuel? (The flight plan is re-optimized for
actual weight changes (passengers or cargo), winds, cruise speed and
altitudes, connections, dropping of choosing a more efficient alternate,
re-optimizing the discretionary fuel, slowing down early flights for
fuel efficiency, etc.)
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- FUEL MANAGEMENT BY CREWS
- Do you have adequate
flight-planning guidelines on fuel management and boarding of additional
fuel, for flight crews?
- Do you have a clear policy on the
alternate selection process? Do you take maximum advantage of aircraft
and airport technology? (CAT II,
CAT III auto-land, better forecasting, traffic information, statistics,
etc)
- Do you have an education and
sensitization program on the boarding of additional discretionary fuel,
the use of statistical discretionary fuel, alternate selection process
and flight planning system optimization?
- Do you have adequate methods of
cross-checking the fuel required for the flight (FMS cross check, etc.)
to avoid unnecessary last minute requests for additional fuel?
- Is access to detailed planning
information available during flight planning? (Weather charts, satellite
photos, airport traffic information, communications with Dispatch, etc)
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- Are airport traffic information and statistics available at flight
planning stations? (Airport demand charts, etc.)
- Do you have guidelines regarding APU management and cost information
(electrical, bleed management) for crews and ground staff?
- Do you have sufficient ground equipment available (GPU, Gate power
supply, air conditioners)?
- Do you have an early departures procedure when passengers boarding and
baggage loading are completed?
(This enables the use of a lower Cost Index (speeds) or minimizes
the need for higher speeds for overscheduled flights)
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150
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- Do you have efficient start-up
and taxi-out procedures?
- Do you have adequate guidelines
for taxi speed management?
- Do you have proper and efficient
engine-out taxi SOPs?
- Do you have a policy and
guideline on departure runway selection and intersection departures when
feasible?
- Do you have a specific guideline
on the most efficient flap setting for takeoff?
- Do you have a rolling take off
policy to reduce fuel consumption, noise and emissions?
- Do you have proper guidelines on
efficient departure profile management using speed versus altitude
trade-off, including best bank angle for efficient turn radius while
minimizing departure procedure distance?
(Use best angle climb speed if heading away from intended course.
Determine if distance or altitude is the restriction)
- Do you retract the flaps (clean
up the aircraft) as soon as possible on departure?
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151
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- Do you have specific SOPs regarding the efficient use of engine and
airframe anti-icing?
- Do you have optimized climb speed
profiles taking weight and winds into consideration? Do you have
appropriate guidance?
- Do you re-optimize the Cost Index
after departure to save fuel for the early arrivals?
- Do you have an overweight landing
procedure to avoid fuel dumping?
- Do you have a post-departure
policy on re-optimization of mission profile and flight plan - based on
estimated arrival time (acceleration and slowdown), zero fuel weight
change, etc?
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- Do you have a passenger
connection management program (Operations Control) and only accelerate
the flights when there is commercial value or when there is a tactical
advantage in doing so?
- Do you have specific guidelines
on Flight Management System (FMS) winds and temperatures insertions?
- Do you have a well-defined air
conditioning systems management procedure for best fuel efficiency while
maintaining passenger comfort?
- Do you have precise crew SOPs
regarding the adherence to flight planned cruise speeds, altitudes and
planned routing including guidelines for tactical decisions?
- Do you have a procedure for
altitude management for short sectors?
- Do you have proper flight control
trimming guidelines for applicable aircraft types?
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153
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- Do you have a step climb policy
for oceanic flight segments and is the flight planning system catering
to OCA step climbs procedures?
- Do you have a speed optimization
process to determine the most efficient Mach number for flights into
fixed Mach areas?
- Do you have guidelines on enroute
flight profile management by crews including proper guidelines and
training for altitude and direct routing management?
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- Do you have a procedure to
minimize the distance traveled when deviating for weather?
- Do you provide accurate winds and
temperatures for the next usable flight levels above and below the
flight planned altitudes?
- Do you consider using less than
the maximum number of air conditioning packs or reduced pack flow with
light passenger loads?
- Do you have a clear policy on
arrival time management and control (ETA Management)?
- Do you have SOPs on holding
procedures, tactical speed and altitude management, information on clean
holding configuration and speeds, lengthening of holding pattern to
minimize turns, shortening of alternate for additional holding time,
etc? (Linear holding is good if
one does not loose an arrival sequence or slot).
- Do you have an effective flight
watch policy, a flight progress monitoring and a flight profile
re-optimization for longer flights?
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- Do you have a policy of advising
flight dispatch of any factor that can affect the present or future
flights? (Weather changes, deviations due to CBs, holdings, diversions,
ground delays, un-forecast winds, unexpected turbulence, etc.)
- Do you maximize the use of
re-clearance and re-dispatching techniques?
- Do you have a clear policy on the
use of alternate fuel to land at destination if holding or contingency
fuels are exceeded while holding? [NOT STATUTORY RESERVE FUEL]
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- Do you have descent profile
management guidelines including speed versus altitude trade-offs, FMS
programming with descent winds and altitude crossing insertions
guidelines?
- Do you have guidelines on arrival
procedures and landing runway selection considerations?
- Are your SOPs specific enough on
Approach planning? Do you have a
policy on keep aircraft clean as long as possible? (If no ATC speed restrictions exist,
recommend the use of speeds that are most efficient as long as possible)
- Is the use of low-noise low-drag
approach procedures (decelerated approach) standard for your airline?
Are the SOPs specific enough with accurate target altitudes and speeds
to maximize the benefits of the procedure?
- Is the use of reduced flap
landings a standard with appropriate guidelines?
- Is the use of idle reverse on
landing encouraged and appropriate information available on fuel versus
brake-wear trade–off? (Carbon
brakes wear is more a function of the number of applications rather than
the amount of braking used. Noise and emissions are reduced and the
passenger reaction is normally favorable. With auto brakes, the stopping
distance is basically the same with or without reverse.)
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- Do you use engine out taxi-in as a standard procedure with appropriate
SOPs?
- Do you start the APU on arrival? Is there a policy of shutting down the
APU as soon as the ground power is available?
- Do you have an APU management policy on short or long turn-around? Do
you have a policy of de-powering the aircraft when unattended?
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- COLLABORATION WITH LOCAL ATS AUTHORITIES
- Have you established a good working arrangement with your local air
traffic authority, to cooperate in airspace, air route and terminal area
design?
- Are your pilots aware of air traffic control procedures and standards,
and the limitations or capabilities of the local ATC systems?
- Do you have a familiarization program for air traffic controllers to
understand the capabilities of your fleet?
- Does your local air traffic authority have a familiarization program for
your pilots?
- Do you have an established process to exchange operational concerns or
complaints with your local air traffic authority?
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Notes
