airliner fuel conservation

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Fuel Conservation

Dave AndersonPerformance Engineering OperationsFlight Operations Engineering

Boeing Commercial AirplanesOctober 2006



2Fuel Conservation

Why Fuel Conservation?



3Fuel Conservation

What is Fuel Conservation?

Fuel conservation means managing the

operation and condition of an airplane tominimize the fuel used on every flight



4Fuel Conservation

*Assumes typical airplane utilization rates

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



5Fuel Conservation

How Much Is This Worth In $$?

Depends on Current Fuel Prices!


http://slidepdf.com/reader/full/airliner-fuel-conservation 6/1496Fuel Conservation

$0.00

$0.20

$0.40

$0.60

$0.80

$1.00

$1.20

$1.40

$1.60

$1.80

$2.00

$2.20

87 89 91 93 95 97 99 01 03 05

Jet Fuel Prices

Year

$ / g a

l l o n

Source: Air Transport World

$0.60

$2.00



Airplane Fuel savings Fuel savings*

type gal/year/airplane $/year/airplane

*Assumes $2.00/gallon


777 70,000 90,000 $140,000 180,000

767 30,000 40,000 $60,000 80,000

757 25,000 35,000 $50,000 70,000

747 100,000 135,000 $200,000 270,000

737 15,000 25,000 $30,000

50,000727 30,000 40,000 $60,000 80,000



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



Total savings =fuel savings

- cost toimplement

Cost to Total Cost

Implement Savings/AP

?? ??

Airplane Fuel savings Fuel savings*

type gal/year/airplane $/year/airplane


777 70,000 90,000 $140,000 180,000

767 30,000 40,000 $60,000 80,000

757 25,000 35,000 $50,000 70,000

747 100,000 135,000 $200,000 270,000

737 15,000

25,000 $30,000

50,000727 30,000 40,000 $60,000 80,000

*Assumes $2.00/gallon



Reducing Fuel Costs Requires Everyone’s Help

• Flight Operations

• Dispatchers

• Flight Crews

• Maintenance

• Management• Fuel Purchasing (Contracts)



FLIGHT

OPERATIONS

ENGINEERING

Operational Practicesfor Fuel Conservation



Flight Operations / Dispatchers

• Reduce Landing Weight

• Load Proper Fuel Reserves

• Load Airplane at Aft C.G.

• Select Minimum Flap that Meets allRequirements

• Fly Optimum Altitudes

• Plan and Fly Efficient Speeds

• Select Shortest Route

• Use Fuel Tankering if Cost Effective

Opportunities For Fuel Conservation



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)



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



% 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



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

R d i U F l



Reducing Unnecessary FuelReduces Landing Weight

• Practice cruise performance monitoring

• Flight plan by tail numbers

• Reduce discretionary fuel



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



19Fuel Conservation

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



20Fuel Conservation

Regulatory Requirements

• Is this an international flight?

• FAA rules?

• ICAO rules?

• Other rules?



21Fuel 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



22Fuel 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 otherweather conditions expected, to fly to destinationairport and thereafter to fly for 2 hours at normal

cruising fuel consumption

FAR 121.645(c)



23Fuel 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)



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



25Fuel 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



26Fuel Conservation

Speed Selection for Holding

• Want to maximize time per kilogram of fuel

• Use published/FMC recommended holdingspeeds



27Fuel Conservation

Use Redispatch to Lower Contingency Fuel

• Reserve/contingency fuel is a function of trip lengthor trip fuel burn

• Originally implemented to cover errors in navigation,weather prediction, etc...

• Navigation and weather forecasting techniques haveimproved, decreasing the chance that contingencyfuel will actually be used

• FAR 121.631 allows dispatch to an airport short of

the intended destination with enroute re-clearance.The conditions of FAR 121.645 must be met at thetime of redispatch with fuel for 10% of the flight timefrom the redispatch point to the destination



28Fuel Conservation

How Redispatch Works

Climb

Descent

Cruise

Intendeddestination

Origin

Redispatch

point

Initialdestination



29Fuel Conservation

IntendeddestinationOrigin

Intended

destinationOrigin

Redispatchpoint

Initialdestination

Redispatch

point

Initialdestination

Off Track Initial Destination



30Fuel Conservation

Fuel Savings

Distance (Time)

Redispatch

point

C o n t i n g e n c

y f u e l

Fuel required

Intendeddestination

Reduction incontingencyfuel required

at landing



31Fuel Conservation

Benefits of Redispatch

Reduced fuel load

Increased payload



32Fuel 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)



33Fuel Conservation

Example of payloadincrease with constant

takeoff weight

OEW

PAYLOAD(1)

Altern+ HoldContingency

TRIPFUEL

TRIPFUEL

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)


PAYLOAD(2)

Redispatch Point C

OEW

TRIP FUEL

Altern+ Hold Contingency

Gross

weight



34Fuel Conservation

Example of takeoffweight and landing

weight decreases with

constant payload

OEW

PAYLOAD(1)


TRIPFUEL

TRIPFUEL

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 Redispatch Point C

OEW

PAYLOAD(2)

PAYLOAD(2)

OEW

TRIP FUEL

Altern+ HoldContingency Contingency 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



35Fuel 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



36Fuel Conservation

737-700 777-200

• Actual variation in drag due to c.g. depends on airplanedesign, weight, altitude and Mach

Airplane Loading (continued)

• Simplified examples of change in drag due to c.g. can befound in the various Performance Engineer’s Manuals

Maintain c.g. in the Mid to Aft Range

.84M trim drag

CG range

14% to 19%

19% to 26%

26% to 37%

37% to 44%

∆CD trim

+2%

+1%

0

-1%

.78M trim drag

CG range

8% to 12%

13% to 18%

19% to 25%

26% to 33%

∆CD trim

+2%

+1%

0

-1%



37Fuel Conservation

Flap Setting

Choose lowest flap setting that will meet takeoffperformance requirements:

• Less drag• Better climb performance

• Spend less time at low altitudes, burn less fuel



38Fuel Conservation

Altitude Selection

Pressure altitude for a given weight and speed

schedule that produces the maximum air miles perunit of fuel

Optimum Altitude Definition



39Fuel 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

460420 380 340

300

O P T I M U M

(CONSTANT MACHNUMBER)



40Fuel 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 90 100 110 120

Pressurealtitude

(1000 ft)



41Fuel Conservation

Step Climb

= Off optimum operations

Optimum Altitude

4000 ft

2000 ft

Stepclimb



42Fuel 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)



43Fuel 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 cruiseLRC = Long Range cruise

1%

LRC Versus MRC

MRC



44Fuel 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



45Fuel 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

Aircraft Type 1

L R

C ( a / c 1 )

L R

C ( a / c 2 )

Fuel For Flying Faster Than MRC

Flying Faster Than LRC?

5000 NM cruise

Time For Flying Faster Than MRC

Aircraft Type 1

AircraftType 2

AircraftType 2



46Fuel 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

High CI high speed, high trip fuel, low trip timeLow CI low speed, low fuel burn, high trip time



47Fuel Conservation

Route Selection

Choose the most favorable route available



48Fuel Conservation

Great Circle

• Shortest ground distance between 2 points on theearth’s surface

• May not be the shortest time when winds areincluded



49Fuel 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!



50Fuel Conservation

Fuel Tankering

Fuel tankering is the practice of carrying

more fuel than required for a particularsector in order to reduce the quantity offuel loaded at the destination airport forthe following sector (or sectors)

What Is It?



51Fuel 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)



52Fuel 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


• Shorter turnaround time

• Limited amount of fuel available• Unreliable airport services

• Fuel quality at destination airport

• Fuel price differential

Why Tanker Fuel?



53Fuel Conservation


• 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



54Fuel Conservation


• 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



55Fuel Conservation

Difficult to quantify, but should be

addressed in all cost calculations


• 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



56Fuel 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



57Fuel 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



58Fuel 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 tankeris not at least equal to their chosen minimum,no fuel will be tankered

C C l l i ( i d)



59Fuel 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 t B ff’ M th d



60Fuel 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



61Fuel 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



62Fuel 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 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)



63Fuel 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)



64Fuel 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



65Fuel 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



66Fuel 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

‘Relative Cost to Tanker’ Method (continued)



67Fuel 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





68Fuel 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 =




69Fuel 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)




70Fuel 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



71Fuel 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



72Fuel Conservation

Flight Crew

Opportunities for Fuel Conservation:

• Practice fuel economy in each phase of flight

• Understand the airplane’s systems - SystemsManagement

Engine Start



73Fuel 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



74Fuel Conservation

Taxi

• Take shortest route possible

• Use minimum thrust and minimum braking

• Taxi with all engines operating?

Taxi



75Fuel 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



76Fuel 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

Takeoff



77Fuel Conservation

Takeoff

• Retract flaps as early as possible

(but, no lower than the minimum

recommended flap retraction height)

• Full rate or derate to save fuel?

Reduced Take Off ThrustImproves Performance Retention



78Fuel 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

TSFC at 1000 Cycles by over 0.4%

(Courtesy of Pratt & Whitney)

Improves Performance Retention

Climb



79Fuel 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



80Fuel 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



81Fuel 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



82Fuel Conservation

Winds

Cruise

• Wind may be a reason to choose an “offoptimum” altitude

• Want to maximize ground miles per unitof fuel burned

• Wind-Altitude trade tables are providedin the operations manual

Wind Effects On Fuel Mileage



83Fuel 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



84Fuel Conservation

777-200ER/PW4090 Example


33 knots greater tailwind (or,lower headwind) would be

required at FL310 relative toFL350 to obtain equivalent

ground fuel mileage




85Fuel 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

777-200 / PW4090Ground fuel mileage, nm/1000 kg

Weight = 220,000 kg

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 Mach Number



86Fuel Conservation

MACH number

G r

o u n d f u e l m i l e a g e

.74 .76 .78 .80 .82

20

40

60

80

100

120

140

.84

767-300ER / RB211-524HGround fuel mileage, nm/1000 kg

Altitude = 35,000 ft, Weight = 140,000 kg

Zero wind

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

737-800 / CFM56-7BGround fuel mileage, nm/1000 kg

Altitude = 35,000 ft, Weight = 68,000 kg

Zero wind

100 kt headwind100 kt headwind

200 kt headwind

200 kt headwind

100 kt tailwind100 kt tailwind

M R C

M R C

L R C

L R C

Examples of the effect of wind on ground fuel

mileage when flying near optimum altitude

Wind Effects On Cruise Mach Number

Zero wind LRCZero wind LRC

Descent



87Fuel 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



88Fuel 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



89Fuel Conservation

pp

• Do not transition to the landing configurationtoo early

• Fuel flow in the landing configuration isapproximately 150% of the fuel flow in theclean configuration

Summary Of Operational Practices



90Fuel Conservation

y p

• Minimize landing weight

• Do not carry more reserve fuel than required

• Use aft C.G. loading if possible

• Use lowest flap setting required

• Target optimum altitude (wind-corrected)

• Target LRC (or cost index)

• Choose most direct routing

• Use benefits of ETOPS routing

• Use tankering where appropriate

Flight Operations / Dispatchers

Summary Of Operational Practices



91Fuel 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



Maintenance Practices forFuel Conservation

Maintenance Personnel



93Fuel Conservation

Opportunities For Fuel Conservation

• Airframe maintenance

• Engine maintenance

• Systems maintenance

Excess Drag Is Lost Payload



94Fuel Conservation

g y

To Offset A 1% Increase In Drag,ZFW Would Need To Be Reduced



95Fuel Conservation

717-200 ≈100 lb (45 kg)737-3/4/500 ≈120 lb (54 kg)

737-6/7/8/900 ≈130 lb (59 kg)

747-400 ≈

1,700 lb (771 kg)757-2/300 ≈260 lb (118 kg)

767-2/300 ≈600 lb (272 kg)

767-400 ≈

750 lb (340 kg)777-200 ≈1,000 lb (454 kg)

777-300 ≈1,100 lb (499 kg)

717-200 ≈ 1,000 lb (454 kg)737-3/4/500 ≈ 1,100 lb (499 kg)

737-6/7/8/900 ≈ 1,200 lb (544 kg)

747-400 ≈

5,800 lb (2,631 kg)757-2/300 ≈ 1,900 lb (862 kg)

767-2/300 ≈ 2,800 lb (1,270 kg)

767-400 ≈

3,200 lb (1,451 kg)777-200 ≈ 4,900 lb (2,222 kg)

777-300 ≈ 5,500 lb (2,495 kg)

Note: Reductions are approximate as actual values vary with distance flown.

ZFW reductions required tomaintain constant takeoff weight

ZFW reductions required tomaintain constant block fuel

Excess Drag Means Wasted FuelExcess Drag Means Wasted Fuel



96Fuel Conservation

• 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

Total Drag Is Composed Of:



97Fuel Conservation

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



98Fuel Conservation

Drag due toairplane sizeand weight

(unavoidable)~ 90%

Pressure, trim andinterference drag(optimized in the

wind tunnel)

~ 6%

Excrescence drag(this can increase)

~ 4%

(For a new airplane at cruise conditions)

What Is Excrescence Drag?



99Fuel 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:



100Fuel Conservation

0

1

2

3

4

Excrescence drag(% airplane drag)

Discrete items

Mismatchesand gaps

Internal airflow & sealleakage

Roughness &

surface irregularities

Total

Discrete Items




• Antennas, masts, lights

• Drag is a function of design, size, position

Mismatched Surfaces




Steps at skin joints, around windows, doors, controlsurfaces, and access panels

Frame

Skin

Internal Airflow




Leaks through gaps,holes, and seals

AirflowAirflow

Roughness(Particularly Bad Near Static Sources)




• Non-flush fasteners, rough surface

• Waviness, gaps

Non Flush Rivet Rough Surface

GapsWaviness

Most Important in Critical Areas




Structural Repair Manuals Identify Critical Areas

747-400

Most Important in Critical Areas




Some Models have ‘Extra Critical’ Areas Identified

737-800

Regular Maintenance Minimizes Deterioration




• Flight control rigging

• Misalignments and mismatches• Aerodynamic seals

• Exterior surface finish

• OEW control

• Engine maintenance

• Instrument calibration

Flight Control Rigging




Out of rig controls and flaps can cause a large

increase in fuel burn

747-400 examples:

• Aileron 1” out of rig ≈ 0.25% fuel

• Spoilers 1,2,3 and 4 up 2” ≈ 0.4% fuel

• Upper and lower rudder offset ≈ 0.35% fuel

• Inboard elevator 2” out of rig ≈ .4% fuel

In-Flight Inspections




Several times during flight:

• Aileron and rudder trim ≈ 5 minutes

• Spoiler misfair ≈ 5 minutes

• Visual check of T.E. ≈ 10 minutes

(difficult to do during revenue service)

Misrigged Ailerons




Misrigged outboard ailerons can resultin an increase in drag and fuel flow

Spoilers




The spoilers begin to rise if the aircraft isbalanced by excessive autopilot lateral input

Control Surface Rigging Check




747 example≈

includes fit and fair check:

• Ailerons ≈ 4 hours (1 - 2 people)

• Spoilers ≈ 2 hours (2 people)

• Flaps and Slats ≈ 3 hours (1 - 2 people)

• Rudders ≈ 3 hours (1 - 2 people)

• Elevators ≈ 2 hours (2 people)



Surface Mismatch




Surface Mismatch – ADF Antenna Fairing – negative step

Surface Mismatch




Engine inlet secondary inlet door mismatch – positive step

Leading Edge Mismatch




727 surface mismatch-R.H. Wing leading edge

slat actuator rod cover - positive stepAirflow

Check for Tight Aircraft Doors




Note the tight and even fit of the airconditioning compartment access doors

Maintain Seals




• Passenger and cargo door seals

• Damaged seals allow air to leak out

• Lose ‘thrust recovery’ from outflow valves• Disrupts flow along the fuselage

Passengerdoors

Fwd cargo

door sealdepressor

before repair

Check for Missing or Damaged Seals




747 R.H. Wing gear well door forward

outboard seal missing and damagedAirflow

Check for Rough Surface Paint




747 rough paint - lower fuselage

Airflow

Maintain a Clean Airplane




• Maintain surface finish

• Fluid leaks contribute to drag

• Periodic washing of exterioris beneficial

– 0.1% drag reduction ifexcessively dirty

– Minimizes metal corrosionand paint damage

– Location of leaks and localdamage

• Customer aesthetics

Approximate Inspection Times for 747-size Aircraft




• 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




Average total airframe drag deterioration ~ 0.65%,

composed mainly of:• Control Surface Rigging ≈ 0.25%

• Deteriorated Seals ≈ 0.20%

• Misfairs ≈ 0.1%

• Roughness ≈ 0.05%

• Other ≈ 0.05%

Remember...




• A well-maintained airplane should not exceed ≈ 0.5%drag increase over its new-airplane level

• Most inspections show less

747-400 Engine Swap Experiment




• 747-400 engine swap experiment in 1996 supported themaximum drag increase for a well-maintained airplane

to be within approximately 0.5%• Engines from a 6-year old airplane with poor fuel mileage

were exchanged with those of a brand new airplane

• Fuel mileage levels were measured before and after theengine exchanges

• The unexplainable portion of the change in fuel mileage

for the same set of engines on an old and new airframewould be attributed to airframe effects only





• First, the old airplane went through a configurationinspection, followed by a D-check

• Control surfaces and seals were repaired, and one newengine was installed, but a known pneumatic systemleak was not fixed (worth ≅ 0.15% in fuel mileage)

• Fuel mileage data was collected both before and afterthe D-check

- 5

- 4

- 3

- 2

- 1

0

F u e l m i l e a g e d e v i a t i o n

F r o m d a t a b a s e

l e v e l ~ %

- 4.1%

- 3.4%

Pre

D-checkPost

D-check

F u e l m i l e a g e d

i f f e r e n c e ~ %

+2

+1

0

+ 0.7%+ 0.3% flightControls

+ 0.4% engineChange

Fuel mileagechange across

the D-check





• Fuel mileage data was collected on both the old

and new airplanes prior to the engine exchange,and following the exchange

• Results from all four sets of data were compared inorder to determine the airframe’s contribution to thedifferences in fuel mileage between the old and newairplanes





F

u e l m i l e a g e d e v i

a t i o n ~ %

- 4

- 3

- 2

- 1

0

1

2

3

F

u e l m i l e a g e d e v i a t i o n ~ %

- 4

- 3

- 2

- 1

0

1

2

3

+ 0.3%

- 0.6%

Newengines

Old airplane New airplane

Improved0.9%

F u e l m i l e a g e d e

v i a t i o n ~ %

- 4

- 3

- 2

- 1

0

1

2

3

- 3.4% F u e l m i l e a g e d e

v i a t i o n ~ %

- 4

- 3

- 2

- 1

0

1

2

3

- 2.6%

Oldengines

Old airplane New airplane

Improved

0.8%





0

.2

.4

.6

.8

1.0

1.2

D

i f f e r e n c e i n f u e l m i l e a g e ~ % Total

difference

0.85%

New verticalfin fairing

0.2%0.1%

0.55%

Pneumaticleakage

Actualdifference

due to drag

- - =

• Because the performance level of the old airplane whenit was first delivered is not known, it is not possible to

determine whether this actual difference is due to dragdeterioration, or just airplane to airplane variability

• For the same set of engines, the old airplane averaged.85% worse than the new airplane

• Is this all due to drag deterioration on the old airplane?

OEW Control




• Operating empty weight (OEW) grows on average+ 0.1% to 0.2% per year, leveling off around 1%in 5 to 10 years

• Most OEW growth is mainly due to:

– Moisture

– Dirt

Engine Maintenance




• 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




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 coolervalves

• Faulty turbine case cooling/Faulty 11th stage cooling valves

Engine Components Are Affected By TheEnvironment In Which They Operate




Typical Engine Deterioration Mechanisms




Increased tip

clearances

Seal leakage

Airfoil

erosion

Dirt

accumulation


Scheduled Refurbishing Recovers SFC and EGT



135Fuel Conservation (Courtesy of Pratt & Whitney)

SFCor

EGT

Hours or cycles

Shopvisit

Shopvisit

Regular shop visits recover SFC and EGT margin,but what can be done between these major visits?

Simple Procedures Can Recover PerformanceBetween Scheduled Shop Visits




On-Wing Engine Washing

• Addresses dirt accumulation

On-Wing Engine Bleed Rigging

• Addresses leakage caused by bleedsystem wear




Sample Impact of Water Wash Frequency

SFC and EGT Can Be Recovered Between ShopVisits Using Repetitive Engine Washes




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

Unwashed

0.75%500 cycle washcumulative benefit

0.5%1000 cycle washcumulative benefit

Sample Impact of Water Wash Frequency

1000 cycle wash

500 cycle wash


On-Wing Water Wash: Costs versus Benefits




Costs

• 6-8 man-hours per wash

• Waste water disposal

• Airplane ‘down’ time

Benefits (estimated annual per engine)

• Fuel savings of $20000 to $30000

• CO2 reduction of 190 to 290 tonnes

• Maintenance cost savings of $4000 to $6000

Note: Assumes 777-type airplane, 6.5 hr cycle, 620 cycles/yr., $1.00/gallon fuel).


On-Wing Engine Bleed RiggingRepair of Leaking Bleed Valves Saves Fuel




• Simple procedure

• Start, stability, service bleeds

• Problem Identified from in-flightperformance trends

Up to 2.5% SFC benefit


p g

Instrument Calibration




• 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




• Keep airspeed system maintained

• Airspeed reads 1% low, you fly 1% fast

• About 2% drag penalty in a 747

Check Static Sources




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!




Don’t let this…Don’t let this…

Become this!Become this!

It Takes the Whole Team to Win

Conclusions




• Large fuel savings results from the accumulationof many smaller fuel-saving actions and policies

• Dispatch, flight operations, flight crews, maintenance,management, and fuel contracts people all need tocontribute

• Program should be tailored to your airline’s specificrequirements and constraints

For More Information

Handout Of Boeing Articles Related To Fuel Conservation




Sources:

• Airliner Magazine

– 1958 to 1997

• Newsletters (self-contained inserts in the Airliner Magazine)

– Fuel Conservation Newsletter - January 1981 toDecember 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

Handout Of Boeing Articles Related To Fuel Conservation

For More Information




• Airplane Maintenance For Fuel Conservation(sign-up sheets available in front of the classroom)

• DC-9, DC-10, and MD-11 specific fuel conservation

documents available upon request

• International Air Transportation Association website:

http://www.iata.org/whatwedo/fuel/fuelaction/fuel_conservation.htm

(Large amount of info here, including document “Guidance Materialand Best Practices for Fuel and Environmental Management”, datedDecember, 2004, which can be downloaded for free)

• ICAO Circular 303 “Operational opportunities to MinimizeFuel Use and Reduce Emissions”, published February,2004

– Can be ordered from ICAO website for $55 USD

http://www.icao.int

Questions?



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