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7/27/2019 Boeing Fuel Conservation Presentation
http://slidepdf.com/reader/full/boeing-fuel-conservation-presentation 1/138
Fuel Conservation
Flight Operations EngineeringBoeing Commercial AirplanesNovember 2004
7/27/2019 Boeing Fuel Conservation Presentation
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2Fuel Conservation
What is Fuel Conservation?
Fuel conservation means managing the
operation and condition of an airplane tominimize the fuel used on every flight
7/27/2019 Boeing Fuel Conservation Presentation
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3Fuel Conservation
*Assumes typical airplane utilization rates. Actual utilization rates may differ.
How Much Is A 1% Reduction In Fuel Worth?
Airplane Fuel savings*
type gal/year/airplane777 70,000 → 90,000
767 30,000 → 40,000
757 25,000 → 35,000
747 100,000 → 135,000
737 15,000 → 25,000
727 30,000 → 40,000
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4Fuel Conservation
How Much Is This Worth In $$?
Depends on Current Fuel Prices!
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5Fuel Conservation
Jet Fuel Prices
Source: Air Transport World
Year
$ / g
a l l o n
$0.00
$0.20
$0.40
$0.60
$0.80
$1.00
$1.20
$1.40
87 89 91 93 95 97 99 01 03
$1.00
7/27/2019 Boeing Fuel Conservation Presentation
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Airplane Fuel savings* Fuel savings*
type gal/year/airplane $/year/airplane
*Assumes $1.00/gallon
How Much Is A 1% Reduction In Fuel Worth?
777 70,000 → 90,000 $70,000 → 90,000
767 30,000 → 40,000 $30,000 → 40,000
757 25,000 → 35,000 $25,000 → 35,000
747 100,000 → 135,000 $100,000 → 135,000
737 15,000→
25,000 $15,000→
25,000727 30,000 → 40,000 $30,000 → 40,000
*Assumes typical airplane utilization rates. Actual utilization rates may differ.
7/27/2019 Boeing Fuel Conservation Presentation
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What Is Fuel ConservationFrom An Airline Business Viewpoint ?
Fuel conservation means managing the
operation and condition of an airplane tominimize the fuel used on every flight
total cost of total cost of
7/27/2019 Boeing Fuel Conservation Presentation
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Total savings =fuel savings
- cost toimplement
Cost to Total Cost
Implement Savings/AP
?? ??
Airplane Fuel savings* Fuel savings*
type gal/year/airplane $/year/airplane
How Much Is A 1% Reduction In Fuel Worth?
777 70,000 → 90,000 $70,000 → 90,000
767 30,000 → 40,000 $30,000 → 40,000
757 25,000 → 35,000 $25,000 → 35,000
747 100,000 → 135,000 $100,000→ 135,000
737 15,000→
25,000 $15,000→
25,000727 30,000 → 40,000 $30,000 → 40,000
*Assumes $1.00/gallon
*Assumes typical airplane utilization rates. Actual utilization rates may differ.
7/27/2019 Boeing Fuel Conservation Presentation
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Saving Fuel Requires Everyone’s Help
• Flight Operations
• Dispatchers
• Flight Crews
• Maintenance
• Management
7/27/2019 Boeing Fuel Conservation Presentation
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FLIGHT
OPERATIONS
ENGINEERING
Operational Practicesfor Fuel Conservation
7/27/2019 Boeing Fuel Conservation Presentation
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Flight Operations / Dispatchers
• Landing weight
• Fuel reserves
• Airplane loading
• Flap selection• Altitude selection
• Speed selection
• Route selection
• Fuel tankering
Opportunities For Fuel Conservation
7/27/2019 Boeing Fuel Conservation Presentation
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Reduced Landing Weight
1% reduction in landing weight produces:
≅ 0.75% reduction in trip fuel (high BPR engines)
≅ 1% reduction in trip fuel (low BPR engines)
7/27/2019 Boeing Fuel Conservation Presentation
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Required AdditionalWLDG = OEW + Payload + reserve + fuel loaded
fuel but not used
Zero fuel weightZero fuel weight
Fuel on board at landingFuel on board at landing
Components Of Landing Weight
7/27/2019 Boeing Fuel Conservation Presentation
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Approximate % Block Fuel Savings Per 1000 Lb (454 Kg) ZFW Reduction
737-3/4/500
737-6/7/8/900
757-200/300
767-2/3/400
777-200/300 747-400
.7% .6% .5% .3% .2% .2%
717-200
.9%
Reducing ZFW Reduces Landing Weight
7/27/2019 Boeing Fuel Conservation Presentation
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Reducing OEW Reduces Landing Weight
• Passenger service items
• Passenger entertainment items
• Empty Cargo and baggage containers
• Unneeded Emergency equipment• Excess Potable water
Items To Consider
7/27/2019 Boeing Fuel Conservation Presentation
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Reducing Unnecessary FuelReduces Landing Weight
• Practice cruise performance monitoring
• Flight plan by tail numbers
7/27/2019 Boeing Fuel Conservation Presentation
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Fuel Reserves
• Carry the appropriate amount of reserves to ensure
a safe flight and to meet your regulatory requirements
• Extra reserves are extra weight
• Airplane burns extra fuel to carry the extra weight
7/27/2019 Boeing Fuel Conservation Presentation
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Fuel Reserves
The amount of required fuel reserves depends on:
• Regulatory requirements
• Choice of alternate airport
• Use of re-dispatch
• Company policies on reserves
• Discretionary fuel
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19Fuel Conservation
Regulatory Requirements
• Is this an international flight?
• FAA rules?
• ICAO rules?
• Other rules?
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20Fuel Conservation
FAA “International Reserves”
(A) To fly to and land at the airport to which it is released;
(B) After that, to fly for a period of 10 percent of the total time required to fly from theairport of departure to, and land at, the airport to which it was released;
(C) After that, to fly to and land at the most distant alternate airport specified in theflight release, if an alternate is required; and
(D) After that, to fly for 30 minutes at holding speed at 1,500 feet above the alternateairport (or the destination airport if no alternate is required) under standardtemperature conditions.
FAR 121.645(b)
DC
B
A
ContingencyContingency
AlternateAlternate
HoldingHolding
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21Fuel Conservation
FAA “Island Reserves”
• No alternate is specified in release under Section121.621(a)(2) or Section 121.623(b).
• Must have enough fuel, considering wind and other weather conditions expected, to fly to destinationairport and thereafter to fly for 2 hours at normal
cruising fuel consumption
FAR 121.645(c)
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22Fuel Conservation
ICAO International
4.3.6.3.1 When an alternate aerodrome is required;
To fly to and execute an approach, and a missed approach,at the aerodrome to which the flight is planned, and
thereafter:
A) To fly to the alternate aerodrome specified in theflight plan; and then
B) To fly for 30 minutes at holding speed at 450 M
(1,500 ft) above the alternate aerodrome under standardtemperature conditions, and approach and land; and
C) To have an additional amount of fuel sufficient toprovide for the increased consumption on the occurrenceof any of the potential contingencies specified by theoperator to the satisfaction of the state of the operator (typically a percentage of the trip fuel: 3% to 6%).
CA
B
ContingencyContingency
HoldingHolding
AlternateAlternate
ICAO Annex 6 (4.3.6.3)
7/27/2019 Boeing Fuel Conservation Presentation
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23Fuel Conservation
Alternate Airport
What items should you consider when choosingan alternate airport?
• Airline facilities
• Size and surface of runway
• Weather
• Hours of operation, lighting
• Fire fighting, rescue equipment
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24Fuel Conservation
Alternate Airport
What items should you consider when choosingan alternate airport?
• Airline facilities
• Size and surface of runway
• Weather
• Hours of operation, lighting
• Fire fighting, rescue equipment
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25Fuel Conservation
Speed Selection for Holding
• Want to maximize time per kilogram of fuel
• Use published/FMC recommended holdingspeeds
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26Fuel Conservation
Use Redispatch to Lower Contingency Fuel
• Reserve/contingency fuel is a function of trip
length or trip fuel burn
• Originally implemented to cover errors innavigation, weather prediction, etc...
• Navigation and weather forecasting techniqueshave improved, decreasing the chance thatcontingency fuel will actually be used
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27Fuel Conservation
How Redispatch Works
Climb
Descent
Cruise
Intendeddestination
Origin
Redispatch
point
Initialdestination
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28Fuel Conservation
IntendeddestinationOrigin
Intended
destinationOrigin
Redispatchpoint
Initialdestination
Redispatch
point
Initialdestination
Off Track Initial Destination
Intent is to lower the Contingency Fuel On
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29Fuel Conservation
Intent is to lower the Contingency Fuel OnBoard at the Final Destination
Distance(Time)
Redispatch
point
Contingencyfuel
C o n t i n g
e n c y F u e
l r e q u i r e d
Intendeddestination
C o n t i n g
e n c y
F u e l r e q u i r e
d
R e d u c t i o
n
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30Fuel Conservation
Reduced fuel load
Increased payload
Benefits of Redispatch
7/27/2019 Boeing Fuel Conservation Presentation
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31Fuel Conservation
B
Initialdestination
A
Origin
C
Finaldestination
Examples of Using Redispatch
To: 1) Increase payload
2) Decrease takeoff and landing weight(by reducing fuel load)
7/27/2019 Boeing Fuel Conservation Presentation
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32Fuel Conservation
Example of payloadincrease with constant
takeoff weight
OEW
PAYLOAD
(1)
Altern + Hold
Contingency
TRIP
FUEL
TRIP
FUEL
Same takeoff weight with andwithout redispatch
O p t i m
u m
r e d i s p
a t c h p o
i n t
A C
OEW
A B
(No redispatch)
PAYLOAD
(2)
Altern + Hold
Contingency
PAYLOAD
(2)
B C
OEW
TRIP FUEL
Altern + Hold Contingency
Gross
weight
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33Fuel Conservation
Example of takeoff weight and landing
weight decreases with
constant payload
OEW
PAYLOAD
(1)
Altern + Hold
Contingency
TRIP
FUEL
TRIP
FUEL
O p t i m
u m
r e d i s p
a t c h p o
i n t
A C
(No redispatch)
A B B C
OEW
PAYLOAD
(2)
PAYLOAD
(2)
OEW
TRIP FUEL
Altern + Hold
ContingencyContingency
Altern + Hold
Takeoff weight decrease
Landing
weight (1)
L a n d i n g
w e i g
h t ( 2 )
( d e c r e
a s e f
r o m ( 1 ) )
Gross
weight
7/27/2019 Boeing Fuel Conservation Presentation
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34Fuel Conservation
WT (fwd c.g.)Lift tail (fwd c.g.)
Lift wing (fwd c.g.)
• At aft c.g. the lift of the tail is less negative than at forwardc.g. due to the smaller moment arm between Liftwing and WT
• Less angle of attack, α, is required to create the lower Liftwing
required to offset the WT plus the less negative Lifttail
• Same Lifttotal, but lower Liftwing and therefore lower α required
Lift wing (aft c.g.)
WT (aft c.g.)
Lift tail (aft c.g.)
<
= Is less negative than
Airplane Loading
Maintain C.G. In The Mid To Aft Range
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35Fuel Conservation
3632282420161284
Center of gravity, %MAC
Incrementalcruise drag, %
-2
-1
0
1
2
3
4
5
0.70
0.65
0.60
0.55
0.50
Typical trim drag increment at cruise Mach
Airplane Loading (continued)
Maintain C.G. in the Mid to Aft Range
W/δ (LB *10-6)
Actual variation indrag due to C.G.
depends on airplanedesign, weight,altitude and Mach
7/27/2019 Boeing Fuel Conservation Presentation
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36Fuel Conservation
Flap Setting
Choose lowest flap setting that will meet takeoff performance requirements:
• Less drag• Better climb performance
• Spend less time at low altitudes, burn less fuel
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37Fuel Conservation
Altitude Selection
Pressure altitude for a given weight and speed
schedule that produces the maximum air miles per unit of fuel
Optimum Altitude Definition
7/27/2019 Boeing Fuel Conservation Presentation
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38Fuel Conservation
Definition of Optimum Altitude
FUEL MILEAGE (NAM/LB)
P R E
S S U R E A L T I T
U D E ( 1 0 0 0 F T )
0.024 0.028 0.032 0.036 0.040 0.044 0.048
30
32
34
36
38
40
GROSS WT(1000 LB)
620
580
540
500
460
420 380 340
300
O P T I M U
M
(CONSTANT MACHNUMBER)
Pressure Altitude Which Provides the Maximum FuelMileage for a Given Weight and Speed
7/27/2019 Boeing Fuel Conservation Presentation
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39Fuel Conservation
LRC Mach
Determining Optimum Altitude
Cruise weight (1000 KG)
Brake release weight (1000 KG)
45
40
35
30 7060 9080 110100 120
70 80 90 100 100 120
Pressurealtitude
(1000 ft)
7/27/2019 Boeing Fuel Conservation Presentation
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40Fuel Conservation
Step Climb
= Off optimum operations
Optimum Altitude
4000 ft
2000 ft
Stepclimb
7/27/2019 Boeing Fuel Conservation Presentation
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41Fuel Conservation
O p t i m u m
a l t i t u d
e
+ 1.5%
+ 1.5%
1000 ft
+ 0.5%
+ 3.0%
+ 0.5%
+ 6.5%
+ 1.5%
+ 8.5%
4-hour Average = + 4.8%
+ 0%
+ 4.5%
4-hour Average = + 0.6%
Off-Optimum Fuel Burn Penalty
4000 ft Step vs. No Step Over a 4-Hour Cruise(Example Only)
7/27/2019 Boeing Fuel Conservation Presentation
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42Fuel Conservation
Speed Selection
NAM/poundfuel
MACH number
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.60 0.64 0.68 0.72 0.76 0.80 0.84
0.05
Increasingweight
LRC
MMO
MRC = Maximum range cruise (speed producing maximum fuel mileage for a given weight)
LRC = Long Range cruise (speed which produces a 1% decrease in FM relative to MRC)
1%
LRC Versus MRC
MRC
7/27/2019 Boeing Fuel Conservation Presentation
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43Fuel Conservation
Speed Selection (continued)
• LRC = MRC + 1% fuel burn
• Significant speed increase for onlya 1% decrease in fuel mileage
• Increases speed stability
• Minimizes throttle adjustments
LRC Versus MRC
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44Fuel Conservation
0
1
2
3
4
5
6
7
8
0.00 0.01 0.02 0.03 0.04
∆ Mach from MRC
∆ F
u e l ~
%
-30
-25
-20
-15
-10
-5
0
0.00 0.01 0.02 0.03 0.04
∆ Mach from MRC
∆ T
i m e ~ m i n .
LRC
Model #1
Model #2
Model #2
Model #1
L R
C
M o d e l # 1
L R
C
M o d e l # 2
∆ Fuel For Flying Faster Than MRC
Flying Faster Than MRC?
Flying faster than LRC typically produces a significant fuelburn increase in return for a relatively small time savings
(example based on 5000 NM cruise)
∆ Time For Flying Faster Than MRC
Actual fuel burn increase, and time decrease, for flying faster thanMRC depends on specific airplane model, weight, and altitude
7/27/2019 Boeing Fuel Conservation Presentation
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45Fuel Conservation
Speed Selection - Other Options
• Cost Index = 0 (maximize ngm/lb
= wind-adjusted MRC)
• Selected Cost Index (minimize costs)
• Maximum Endurance (maximize time/lb)
CI =Time cost ~ $/hr
Fuel cost ~ cents/lb
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46Fuel Conservation
Route Selection
Choose the most favorable route available!
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47Fuel Conservation
Great Circle Distance
• Shortest ground distance between 2 points on theearth’s surface
• May not be the shortest time when winds areincluded
7/27/2019 Boeing Fuel Conservation Presentation
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48Fuel Conservation
ETOPS
• ETOPS allows for more direct routes
• Shorter routes = less fuel required
New York
Montreal
St. Johns
Goose Bay
IqaluitKangerlussuaq
Reykjavik
Shannon Paris
1 2 0 m i n
6 0 m i n
31 4 8
3 4 6 1
Using 120 min ETOPS leads to
a 9% savings in trip distance!
7/27/2019 Boeing Fuel Conservation Presentation
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49Fuel Conservation
Fuel Tankering
Fuel tankering is the practice of carrying
more fuel than required for a particular sector in order to reduce the quantity of fuel loaded at the destination airport for the following sector (or sectors)
What Is It?
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50Fuel Conservation
A B C
Leg 1 Leg 2
Reserves
Fuelfor
leg 2
Fuelfor
leg 2
Fuelfor
leg 1
Fuelfor
leg 1
Fuel loaded at A for leg 1Fuel loaded at
B for leg 2
No tankeringof 2nd leg fuel
Reserves
Extra fuel burnedon leg 1 to carry
fuel for leg 2 Fuelfor
leg 2
Fuelfor
leg 2
Fuelfor
leg 1
Fuelfor
leg 1
100% tankeringof 2nd leg fuel
Fuel loadedat A for legs 1 & 2
Fuel Tankering (continued)
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51Fuel Conservation
Reduction in total fuel costs for multiple legflights is usually the main reason for tankering
Reduction in total fuel costs for multiple legflights is usually the main reason for tankering
Fuel Tankering (continued)
• Shorter turnaround time
• Limited amount of fuel available• Unreliable airport services
• Fuel quality at destination airport
• Fuel price differential
Why Tanker Fuel?
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52Fuel Conservation
Fuel Tankering (continued)
• If price at departure airport is sufficiently less than at thedestination airport, surplus fuel could be carried fromthe departure airport to lower the total fuel cost
• Fuel used increases on flights where fuel is tankeredsuch that the quantity of fuel available at landing is
always less than what was originally loaded (oftencalled ‘surplus fuel burn-off’)
• Surplus fuel burn-off must be accounted for in any pricedifferential calculation
• To be cost-effective, the difference in fuel price betweenthe departure and destination airports must be largeenough to offset the cost of the additional fuel burned
in carrying the tankered fuel
Fuel Price Differential
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53Fuel Conservation
Fuel Tankering (continued)
• The amount of tankered fuel loaded may
be limited by: – Certified MTOW
– Performance-limited MTOW
– Certified MLW – Performance-limited MLW
– Fuel capacity
• These limits must always be checked whenloading extra fuel for tankering!
Limitations On Total Amounts
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54Fuel Conservation
Difficult to quantify, but should be
addressed in all cost calculations
Fuel Tankering (continued)
• Lowers initial cruise altitude capability
• Increases takeoff weight: higher takeoff speeds,less reduced thrust, may require improved climb
• If landing is planned at or near MLW, and additional
fuel burn-off was over-predicted, an overweightlanding could result
• Higher maintenance costs: engines, reversers,wheels, tires, brakes
Additional Considerations
7/27/2019 Boeing Fuel Conservation Presentation
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55Fuel Conservation
To Tanker or Not to Tanker
• Cost calculations vary between operators, ranging
from the fairly simple to the fairly complex
• Complexity of the calculations depends on therequirements of your operations. (e.g., If the
decision to tanker is made by the captain at thetime of fueling, a simple method is desired)
• Many operators add a price per gallon, or a fixed
percentage, to cover increased maintenance costs
Cost Calculations
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56Fuel Conservation
Cost Calculations
We will briefly review 3 possible methods:
1) Assumed percentage burn-off
2) Break-even price ratio
3) Relative cost to tanker
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57Fuel Conservation
Cost Calculations (continued)
• All methods should begin by checking whether
takeoff and landing weight limits, along with fuelcapacity limits, allow additional fuel to be loaded
• Some operators choose a minimum tankering
amount such that if the amount available to tanker is not at least equal to their chosen minimum,no fuel will be tankered
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58Fuel Conservation
Cost Calculations (continued)
Calculation of fuel prices is not always as easyas it first appears. Understand how fuel prices are
determined at your airline.
For example:
• Price may vary with amount purchased
• Fixed hookup fees should be included (affectsprice per gallon - as more fuel is purchased,the hookup price/gallon decreases)
• Taxes charged may be returned later as taxrebates lower the price per gallon
‘A d P B ff’ M h d
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59Fuel Conservation
‘Assumed Percentage Burn-off’ Method
• Assumes a fixed percentage of the tankered fuelis consumed per hour of flight time; usually 4 to 5%per hour
• Divide total cost of additional fuel purchasedat departure airport by amount remaining atdestination airport to determine ‘effective’ price
of fuel at destination
• Assume some per gallon cost to cover unknowns
• Break-even price is the ‘effective’ price plus theallowance for unknown costs
• If price of fuel at destination is above the breakeven
price, then it is cost-effective to tanker
E l C t C l l ti
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60Fuel Conservation
Example Cost Calculation
• Planned flight time = 6 hours
• Departure fuel price = $1.00/gallon
• Tankered fuel loaded = 40000 lb (6000 gallons)
• Cost of tankered fuel = $6000
• Surplus fuel burn-off (4%/hour) = 24%
• Tankered fuel at landing = 6000 x .76 = 4560 gallons
• Effective cost of tankered fuel = 6000/4560 = $1.32/gal
• Allowance for unknown cost = $.02/gal (typical?)• Actual cost of tankered fuel = $1.32 + $.02 = $1.34/gal
• Cost-effective if destination fuel price above $1.34/gal
B k E P i R ti M th d
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61Fuel Conservation
Trip distance (nm) Break-even price ratio
200
400
600
8001000
2000
3000
4000
5000
6000
1.012
1.023
1.034
1.0461.061
1.130
1.217
1.334
1.495
1.722
S a m p l e d a t a
o n l y
v a r i e s
w i t h
a i r p
l a n e m o d
e l
S a m p l e d a t a
o n l y
v a r i e s
w i t h
a i r p
l a n e m o d
e l
• To economically justify tanker operation, the fuel
price at the destination must be greater than thebreak-even fuel price
Break-Even Price Ratio Method
• Method used in Boeing FPPM (found in chapter 2 text)• Break-even price ratio is presented as a function of trip
distance only
B k E P i R ti M th d ( ti d)
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62Fuel Conservation
$ * (tankered fuel) = $ * (tankered fuel - fuel burnoff)gal gal
Orig Dest = tankered fuelremaining at dest
Break-evenprice ratio
Orig
$gal Dest
B.E.
$gal *=Break-even price =
at destination
Break-Even Price Ratio Method (continued)
• Break-even fuel price is the destination price at which thecost of purchasing the fuel at the destination is equivalentto the cost of purchasing the same amount of fuel, plusthe fuel required to carry it, at the origin
• Break-even price occurs when:
B k E P i R ti M th d ( ti d)
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63Fuel Conservation
Break-Even Price Ratio Method (continued)
• If the destination fuel price is greater than the break-
even price, then it’s cheaper to tanker the fuel
• The break-even price ratio does not include anyallowance for additional maintenance costs; it only
considers the extra fuel burn off
E l C t C l l ti
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64Fuel Conservation
Example Cost Calculation
Fuel price at origin: $0.80/gal
Model: 737-700/CFM56-7B24Trip distance: 2000 NM
Trip distance, nm Break-even price ratio
200
400600800
1000200030004000
1.015
1.0311.0451.0591.0751.1751.3111.477
Break-even price = $0.80 ( 1.175) = $0.94
If dest. fuel price > $0.94, then more economical to tanker the fuelIf dest. fuel price < $0.94, then more economical to purchase at dest.
To include increased maintenance costs, should increase the B.E.
fuel price by the estimate (e.g., if unknown costs estimated at$0.02/gal, then B.E. fuel price = $0.94 + $0.02 = $0.96)
‘R l ti C t t T k ’ M th d
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65Fuel Conservation
‘Relative Cost to Tanker’ Method
• Considers the difference in total cost between
tankering and not tankering the fuel
• Only includes costs related to tankering or nottankering fuel
• Requires calculation of fuel required for actualroutes with and without tankering
‘R l ti C t t T k ’ M th d ( ti d)
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66Fuel Conservation
A B C
Leg 1 Leg 2
gal A
$ Fuelreq’dleg 1
Fuelcarriedfor usein leg 2
+Extra fuelburned on
leg 1 due toextra wt
+ + Additionalincrementalcosts due tohigher weight
galB
$+
Additionalfuel req’dfor leg 2
*
total cost with tankering
-gal
B
$Fuelreq’dleg 1
-gal
A
$ Fuelreq’dleg 2
**
Total cost with no tankering
‘Relative Cost to Tanker’ Method (continued)
‘Relative Cost to Tanker’ Method (continued)
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67Fuel Conservation
cost of tankering the fuel cost of purchasingat the destination
galB
$fuelcarriedfor usein leg 2
+
extra fuelburned on
leg 1 due toextra weight
+
additionalincrementalcosts due to
higher weight
- *gal
A
$fuel
carriedfor usein leg 2
‘Relative Cost to Tanker’ Method (continued)
Relative cost to tanker =
‘Relative Cost to Tanker’ Method (continued)
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68Fuel Conservation
• If relative cost to tanker = 0, then breakeven
• If relative cost to tanker > 0, then costs are increasedby tankering
• If relative cost to tanker < 0, then costs are reducedby tankering
• Some operators choose a minimum financial gain belowwhich there will not be tankering. (e.g., if minimum gainselected as $100, then tankering will only be used if
relative cost to tanker < - $100)
• Multiple legs (3 or more) add significantly to the complexityof the analysis
‘Relative Cost to Tanker’ Method (continued)
‘Relative Cost to Tanker’ Method (continued)
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69Fuel Conservation
Additional Applications
• If fuel is tankered in order to obtain a shorter turnaround
time at a given destination you can determine therelative cost of the shorter turnaround time
• Cost to tanker can be used to provide flight crews
with information on the cost of carrying additional,discretionary fuel
Relative Cost to Tanker Method (continued)
Fuel Tankering
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70Fuel Conservation
Fuel Tankering
• Most flight planning services offer tankering
analyses to their customers
• You can work with your flight planning service onwhich assumptions to use/include, and in what form
the results should be reported
Flight Crew
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71Fuel Conservation
Flight Crew
Opportunities for Fuel Conservation:
• Practice fuel economy in each phase of flight
• Understand the airplane’s systems - SystemsManagement
Engine Start
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72Fuel Conservation
Engine Start
• Start engines as late as possible, coordinatewith ATC departure schedule
• Take delays at the gate if possible
• Minimize APU use if ground power available
Taxi
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73Fuel Conservation
Taxi
• Take shortest route possible
• Use minimum thrust and minimum braking
• Taxi with all engines operating?
Taxi
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74Fuel Conservation
Taxi
• After-start and before-takeoff checklists delayed
• Reduced fire protection from ground personnel• High weights, soft asphalt, taxi-way slope
• Engine thermal stabilization - warm up and cool down
• Pneumatic and electrical system requirements
• Slow/tight turns in direction of operating engine(s)
• Cross-bleed start requirements
Balance fuel conservation and safety considerations
One Engine Shut Down Considerations:
Sample Taxi and APU Fuel Burns
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75Fuel Conservation
Condition 727 737 747 757 767 777
Taxi*(lb/min)
60 25 100 40 50 60
APU(lb/min)
5 4 11 4 4 9
717
25
4
Sample Taxi and APU Fuel Burns
* Assumes all engines operating during taxi
Takeoff
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76Fuel Conservation
Takeoff
• Retract flaps as early as possible
• Full rate or derate to save fuel?
(Use of full rate will save fuel for a given takeoff, but general consensus is that inthe long-term, total costs will be reduced by using reduced takeoff thrust)
Reduced Take Off ThrustImproves Long-term Performance Retention
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77Fuel Conservation
-1.0%
-0.9%
-0.8%
-0.7%
-0.6%
-0.5%
-0.4%
-0.3%
-0.2%
-0.1%
0.0%
-25% -20% -15% -10% -5% 0%
Average takeoff thrust reduction (% from full rate)
∆
T S F C @ 1
0 0 0 c y c l e s
Estimated Reduced ThrustImpact at 1000 Cycles
15% Average Thrust Reduction Can Improve
Overall TSFC at 1000 Cycles by over 0.4%
(Courtesy of Pratt & Whitney)
Improves Long-term Performance Retention
Climb
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78Fuel Conservation
Distance
Altitude
Initial cruisealtitude
Cost index
increasing
A
B
C I = 0
( M
i n f u e l )
M i n t
i m e t
o P o i n t
B
M a x
g r a
d i e
n t
Climb
Cost Index = 0 minimizes fuel to climb andcruise to a common point in space
Cruise
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79Fuel Conservation
Cruise
• A plane flying in steady, level flight may requiresome control surface inputs to maintain lateral-directional control
• Use of the proper trim procedureminimizes drag
• Poor trim procedure canresult in a 0.5% cruisedrag penalty on a 747
• Follow the proceduresprovided in the FlightCrew Training Manual
Lateral - Directional Trim Procedure
Cruise
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80Fuel Conservation
Systems Management
Cruise
• A/C packs in high flow typically produce
a 0.5 - 1 % increase in fuel burn
• Do not use unnecessary cargo heat
• Do not use unnecessary anti-ice
• Maintain a balanced fuel load
Cruise
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81Fuel Conservation
Winds
Cruise
• Wind may be a reason to choose an “off optimum” altitude
• Want to maximize ground miles per unitof fuel burned
• Wind-Altitude trade tables are providedin the flight crew operations manual
Wind Effects On Fuel Mileage
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82Fuel Conservation
Fuel Mileage = =Fuel Flow
VTAS
KG
NAM
Fuel Used = =
NGM/KG
NGM
NAM/KG
NAM
=
VTAS + VWIND
(NGM) (Fuel Flow)
Ground Fuel Mileage = =Fuel Flow
VTAS + VWIND
KG
NGM
In cruise: positive wind = Tailwind
negative wind = Headwind
V G r o u n d
Wind Effects On Fuel Mileage
Wind Effects On Cruise Altitude: Wind/Alt Trade
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83Fuel Conservation
Typical Wind/Altitude Trade Table
Wind Effects On Cruise Altitude: Wind/Alt Trade
33 knots greater tailwind (or,lower headwind) would be
required at FL310 relative toFL350 to obtain equivalent
ground fuel mileage
Wind Effects On Cruise Altitude: Wind/Alt Trade
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84Fuel Conservation
MACH number
G r o u n d f u e l m
i l e a g e
.80 .81 .82 .83 .84 .85 .8664
66
68
70
72
74
76
78
35 K , W i nd = 0
3 1K , W i nd = 0
MACH number
G r o u n d f u e l m
i l e a g e
.80 .81 .82 .83 .84 .85 .8664
66
68
70
72
74
76
78
35K , W ind = 0
3 1K , W i nd = 0
W i nd = 10
W i nd = 2 0
W i nd = 3 0
W i nd = 4 0
LRC, 35K
Typical Wind Altitude/Trade for Constant Airplane Weight
Example of increasing Tailwind at 31,000 ft Example of increasing headwind at 35,000 ft
LRC, 31K
LRC, 31K
LRC, 35K
W i nd = - 10
W i nd = - 2 0
W ind = - 30
W i nd = - 4 0
Wind Effects On Cruise Altitude: Wind/Alt Trade
* Actual ground fuel mileage comparisons vary with airplane model,weight, and altitudes considered
Wind Effects On Cruise Mach Number
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85Fuel Conservation
G r o u n d f u e l m
i l e a g e
60
80
100
120
140
160
180
200
220
240
.72 .73 .74 .75 .76 .77 .78 .79 .80 .81 .82
MACH number
Zero wind
100 kt headwind
200 kt headwind
100 kt tailwind
M R C
L R C
Typical affect of wind on ground fuel mileage whenflying a constant altitude and weight
Wind Effects On Cruise Mach Number
Zero wind LRC
* Actual ground fuel mileage comparisons vary with airplane model,weight, and altitudes considered
Descent
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86Fuel Conservation
Descent
• Penalty for early descent - spend more time at lowaltitudes, higher fuel burn
• Optimum top of descent point is affected by wind, ATC, speed restrictions, etc.
• Use information provided by FMC
• Use idle thrust (no part-power descents)
Descent
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87Fuel Conservation
Distance
Final cruisealtitude
Cost index
increasing
B
C I = 0 ( M
i n f u e l )
M i n t i m
e f r o
m p o i n t A
t o B
Descent
Cost Index = 0 minimizes fuel between a commoncruise point and a common end of descent point
Altitude
A
Approach
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88Fuel Conservation
Approach
• Do not transition to the landing configurationtoo early
• Fuel flow in the landing configuration isapproximately 150% of the fuel flow in theclean configuration
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Summary Of Operational Practices
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90Fuel Conservation
Flight Crews
y p
• Minimize engine/APU use on ground
• Retract Flaps as early as possible• Fly the flight-planned speeds for all
phases of flight
• Use proper trim procedures
• Understand the airplane’s systems
• Understand wind/altitude trades• Don’t descend too early (or too late)
• Don’t transition to landing configuration
too early
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Maintenance Practices for Fuel Conservation
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Excess Drag Is Lost Payload
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93Fuel Conservation
g y
Excess Drag Means Wasted FuelExcess Drag Means Wasted Fuel
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94Fuel Conservation
g
• 747 ≈ 100,000
• 777 ≈ 70,000
• 767 ≈ 30,000
• 757 ≈ 25,000
• 737 ≈ 15,000
• 727 ≈ 30,000
1% Drag In Terms Of Gallons Per Year
* Assumes typical airplane utilization rates. Actual utilization rates may differ.
Total Drag Is Composed Of:
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95Fuel Conservation
g p
Compressible drag ≈ drag due to Mach
• Shock waves, separated flow
Induced (vortex) drag ≈ drag due to lift
• Downwash behind wing, trim drag
Parasite drag ≈ drag not due to lift
• Shape of the body, skin friction, leakage,interference between components
• Parasite drag includes excrescence drag
Contributors To Total Airplane Drag
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96Fuel Conservation
Drag due toairplane sizeand weight
(unavoidable)~ 90%
Pressure, trim andinterference drag(optimized in the
wind tunnel)
~ 6%
Excrescence drag(this can increase)
~ 4%
p g
(New Airplane at Cruise Conditions)
* Typical values for illustration purposes. Actual magnitudes vary with airplane model
What Is Excrescence Drag?
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97Fuel Conservation
The additional drag on the airplane due
to the sum of all deviations from asmooth sealed external surface
Proper maintenance can prevent anincrease in excrescence drag
Excrescence Drag On A ‘New Airplane’ Is Composed Of:
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98Fuel Conservation
0
1
2
3
4
Excrescence drag(% airplane drag)
Discrete items
Mismatchesand gaps
Internal airflow & sealleakage
Roughness &
surface irregularities
Total
* Typical values for illustration purposes. Actual magnitudes vary with airplane model
Discrete Items
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99Fuel Conservation
• Antennas, masts, lights
• Drag is a function of design, size, position
Mismatched Surfaces
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100Fuel Conservation
Steps and gaps at skin joints, around windows, doors,control surfaces, and access panels
Frame
Skin
Internal Airflow
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101Fuel Conservation
Leaks from higher to lower pressure areas due to
deteriorated or poorly-installedaerodynamic seals
AirflowAirflow
Roughness(Particularly Bad Near Static Sources)
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102Fuel Conservation
• Non-flush fasteners, rough surface
• Waviness, gaps
Non Flush Rivet Rough Surface
GapsWaviness
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Regular Maintenance Minimizes Deterioration
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104Fuel Conservation
• Flight control rigging
• Misalignments and mismatches• Aerodynamic seals
• Exterior surface finish
• OEW control
• Engine maintenance
• Instrument calibration
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In-Flight Inspections Can be Easily Made
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106Fuel Conservation
Several times during flight:
• Note required aileron and rudder trim ≈ 5 minutes
• Visual check of spoiler misfair ≈ 5 minutes
• Visual check of trailing edge of wing ≈ 10 minutes
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Spoilers
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108Fuel Conservation
The spoilers can begin to rise if the aircraft isbalanced by excessive autopilot lateral input
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Misalignment, Mismatch
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110Fuel Conservation
Check items which are adjustable and could
become misaligned after years of service:• Adjustable panels
• Landing gear doors
• Entry doors and cargo doors
Surface Mismatch
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111Fuel Conservation
Surface Mismatch – ADF Antenna Fairing – negative step
Surface Mismatch
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112Fuel Conservation
Engine inlet secondary inlet door mismatch – positive step
Leading Edge Mismatch
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113Fuel Conservation
727 surface mismatch-R.H. Wing leading edge
slat actuator rod cover - positive stepAirflow
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Maintain Seals
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116Fuel Conservation
• Passenger and cargo door seals
• Damaged seals allow air to leak out
• Lose ‘thrust recovery’ from outflow valves• Disrupts flow along the fuselage
Passenger doors
Fwd cargo
door sealdepressor
before repair
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Maintain a Clean Airplane
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119Fuel Conservation
• Maintain surface finish
• Fluid leaks contribute to drag
• Periodic washing of exterior is beneficial
– 0.1% drag reduction if excessively dirty
– Minimizes metal corrosionand paint damage
– Location of leaks and localdamage
• Customer aesthetics
Make Simple Inspections
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120Fuel Conservation
• Seal inspections ≈ 1 hour
• Nacelles and struts ≈ 2 hours
• Wing/body/tail misfairs ≈ 2 hours
• General roughness and appearance ≈ 1 hour • Pressurized fuselage leak ≈ 2 hours
• Landing gear door check ≈ 1.5 hours
Average Results Of In-service Drag Inspections
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121Fuel Conservation
• Results of in-service airframe drag inspections show the
most common contributors to airframe deterioration are: – Control surface miss-rigging
– Aerodynamic seal deterioration
• Lesser contributors include:
– Skin surface miss-matches
– Surface roughness
– ‘Other’
OEW Control
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122Fuel Conservation
• Operating empty weight (OEW) typically increases0.1% to 0.2% per year, leveling off around +1% froma new-airplane level in 5 to 10 years
• Most OEW growth is mainly due to accumulation of:
– Moisture
– Dirt
Engine Maintenance
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123Fuel Conservation
• Need to balance savings from performanceimprovements versus cost to perform maintenance
• Maintenance performed on high and low pressureturbines and compressors will help keep fuelconsumption from deteriorating
Items That Cause Engine/Fuel Burndeterioration
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124Fuel Conservation
Erosion / Wear / Contamination• Blade rubs - HP compressor, HP turbine, airfoil blade erosion
• Thermal distortion of blade parts
• Blade leading edge wear
• Excessive fan rubstrip wear
• Lining loss in the HP compressor
• Oil or dirt contamination of LP/HP compressor
Seals / Valves / Cooling
• Loss of High Pressure Turbine (HPT) outer air seal material
• Leaking thrust reverser seals
• ECS anomalies/leaks
• Failed-open fan air valves/Failed-open IDG air-oil cooler valves
• Faulty turbine case cooling/Faulty 11th stage cooling valves
Engine Components Are Affected By TheEnvironment In Which They Operate
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125Fuel Conservation
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Simple Procedures Can Recover PerformanceBetween Scheduled Shop Visits
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128Fuel Conservation
On-Wing Engine Washing
• Addresses dirt accumulation
On-Wing Engine Bleed Rigging
• Addresses leakage caused by bleedsystem wear
(Courtesy of Pratt & Whitney)
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SFC and EGT Can Be Recovered Between ShopVisits Using Repetitive Engine Washes
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130Fuel Conservation
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 1000 2000 3000 4000 5000 6000
Cycles
% ∆TSFC
1000 cycle wash
Unwashed
500 cycle wash
0.5%1000 cycle washcumulative benefit
0.75%500 cycle washcumulative benefit
Example of Water Wash Frequency Impact
(Courtesy of Pratt & Whitney)
On-Wing Engine Bleed RiggingRepair of Leaking Bleed Valves Saves Fuel
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131Fuel Conservation
• Simple procedure
• Start, stability, service bleeds
• Problem Identified from in-flightperformance trends
Up to 2.5% SFC benefitpossible
Repair of Leaking Bleed Valves Saves Fuel
(Courtesy of Pratt & Whitney)
Instrument Calibration
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132Fuel Conservation
• Speed measuring equipment has a large impacton fuel mileage
• If speed is not accurate the airplane may be flyingfaster or slower than intended
• On the 747-400, flying 0.01M faster can increase
fuel burn by 1% or more
Airspeed System Error Penalty
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133Fuel Conservation
• Keep airspeed system calibrated
• Airspeed reads 1% low, airplane flies 1% fast
• About 2% drag penalty in a 747
Check Static Sources
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134Fuel Conservation
Plugging or deforming the holes in the alternate static port can result
in erroneous instrument readings in the flight deck. Keeping thecircled area smooth and clean promotes aerodynamic efficiency.
Proper and Continuous Airframe and Engine MaintenanceWill Keep Your Airplanes Performing at Their Best!
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135Fuel Conservation
Don’t let this…Don’t let this…
Become this!Become this!
It Takes the Whole Team to Win
Conclusions
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136Fuel Conservation
It Takes the Whole Team to Win
• Large fuel savings results from the accumulationof many smaller fuel-saving actions and policies
• Dispatch, flight operations, flight crews, maintenance,and management all need to contribute
• Program should be tailored to your airline’s needs andrequirements
For More Information
Boeing has published numerous articles addressing fuel
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137Fuel Conservation
• Airliner Magazine
– 1958 to 1997
• Newsletters (self-contained inserts in the Airliner Magazine)
– Fuel Conservation Newsletter - January 1981 to
December 1983
– Fuel Conservation & Operations Newsletter - January 1984to June 1994
– Operations Newsletter - July 1994 to December 1997
• Aero Magazine (replaced Airliner after Boeing - MDC merger)
– January 1998 to 2003
Boeing has published numerous articles addressing fuelconservation over the last 4 decades in the following publications:
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End of Fuel Conservation
Flight Operations Engineering
Boeing Commercial AirplanesNovember 2004