Fuel Conservation

Fuel Conservation

Flight Operations EngineeringBoeing Commercial Airplanes

November 2004

2Fuel Conservation

What is Fuel Conservation?

Fuel conservation means managing the operation and condition of an airplane to minimize the fuel used on every flight

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/airplane

777 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

4Fuel Conservation

How Much Is This Worth In $$?

Depends on Current Fuel Prices!

5Fuel Conservation

Jet Fuel Prices

Source: Air Transport WorldYear

$/ga

llon

$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

6Fuel Conservation

Airplane Fuel savings* Fuel savings*type gal/year/airplane $/year/airplane

*Assumes $1.00/gallon


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 → 25,000

727 30,000 →40,000 $30,000 → 40,000

*Assumes typical airplane utilization rates. Actual utilization rates may differ.

7Fuel Conservation

What Is Fuel Conservation From An Airline Business Viewpoint ?

Fuel conservation means managing the operation and condition of an airplane to minimize the fuel used on every flight

total cost oftotal cost of

8Fuel Conservation

Total savings =fuel savings

- cost to implement

Cost to Total CostImplement Savings/AP

?? ??

Airplane Fuel savings* Fuel savings*type gal/year/airplane $/year/airplane


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 →25,000

727 30,000 →40,000 $30,000 →40,000

*Assumes $1.00/gallon*Assumes typical airplane utilization rates. Actual utilization rates may differ.

9Fuel Conservation

Saving Fuel Requires Everyone’s Help

• Flight Operations

• Dispatchers

• Flight Crews

• Maintenance

• Management

10

FLIGHTOPERATIONS

ENGINEERING

Operational Practices for Fuel Conservation

11Fuel Conservation

Flight Operations / Dispatchers

• Landing weight

• Fuel reserves

• Airplane loading

• Flap selection

• Altitude selection

• Speed selection

• Route selection

• Fuel tankering

Opportunities For Fuel Conservation

12Fuel 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)

13Fuel Conservation

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

14Fuel Conservation

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

15Fuel Conservation

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

16Fuel Conservation

Reducing Unnecessary Fuel Reduces Landing Weight

• Practice cruise performance monitoring

• Flight plan by tail numbers

17Fuel Conservation

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

18Fuel 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

19Fuel Conservation

Regulatory Requirements

• Is this an international flight?

• FAA rules?

• ICAO rules?

• Other rules?

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 the airport 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 alternate airport (or the destination airport if no alternate is required) under standard temperature conditions.

FAR 121.645(b)

DC

B

A

ContingencyContingency

AlternateAlternate

HoldingHolding

21Fuel Conservation

FAA “Island Reserves”

• No alternate is specified in release under Section 121.621(a)(2) or Section 121.623(b).

• Must have enough fuel, considering wind and other weather conditions expected, to fly to destination airport and thereafter to fly for 2 hours at normal cruising fuel consumption

FAR 121.645(c)

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 the flight plan; and then

B) To fly for 30 minutes at holding speed at 450 M (1,500 ft) above the alternate aerodrome under standard temperature conditions, and approach and land; and

C) To have an additional amount of fuel sufficient to provide for the increased consumption on the occurrence of any of the potential contingencies specified by the operator to the satisfaction of the state of the operator (typically a percentage of the trip fuel: 3% to 6%).

CA

B

ContingencyContingency

HoldingHoldingAlternateAlternate

ICAO Annex 6 (4.3.6.3)

23Fuel Conservation

Alternate Airport

What items should you consider when choosing an alternate airport?

• Airline facilities

• Size and surface of runway

• Weather

• Hours of operation, lighting

• Fire fighting, rescue equipment

24Fuel Conservation

Alternate Airport

What items should you consider when choosing an alternate airport?

• Airline facilities

• Size and surface of runway

• Weather

• Hours of operation, lighting

• Fire fighting, rescue equipment

25Fuel Conservation

Speed Selection for Holding

• Want to maximize time per kilogram of fuel

• Use published/FMC recommended holding speeds

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 in navigation, weather prediction, etc...

• Navigation and weather forecasting techniques have improved, decreasing the chance that contingency fuel will actually be used

27Fuel Conservation

How Redispatch Works

Climb

Descent

Cruise

Intended destination

Origin

Redispatchpoint

Initialdestination

28Fuel Conservation

Intendeddestination Origin

Intendeddestination Origin

Redispatchpoint

Initialdestination

Redispatchpoint

Initialdestination

Off Track Initial Destination

29Fuel Conservation

Intent is to lower the Contingency Fuel On Board at the Final Destination

Distance (Time)

Redispatchpoint

Contingencyfuel

Contingency Fuel required

Intended destination

Contingency

Fuel required

Red

uctio

n

30Fuel Conservation

Reduced fuel load

Increased payload

Benefits of Redispatch

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)

32Fuel Conservation

Example of payload increase with constant

takeoff weight

OEW

PAYLOAD(1)

Altern + HoldContingency

TRIPFUEL

TRIPFUEL

Same takeoff weight with and without redispatch

Optimum

redispatchpoint

A C

OEW

A B(No redispatch)

PAYLOAD(2)


PAYLOAD(2)

B C

OEW

TRIP FUELAltern + Hold

ContingencyGross weight

33Fuel Conservation

Example of takeoff weight and landing

weight decreases with constant payload

OEW

PAYLOAD(1)


TRIPFUEL

TRIPFUEL

Optimum

redispatchpoint

A C(No redispatch)

A B B C

OEW

PAYLOAD(2)

PAYLOAD(2)

OEW

TRIP FUEL

Altern + HoldContingency ContingencyAltern + Hold

Takeoff weight decrease

Landing weight (1)

Landing weight (2)

(decrease fro

m (1))

Gross weight

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 forward c.g. due to the smaller moment arm between Liftwing and WT

• Less angle of attack, α, is required to create the lower Liftwingrequired 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 LoadingMaintain C.G. In The Mid To Aft Range

35Fuel Conservation

3632282420161284

Center of gravity, %MAC

Incremental cruise drag, %

-2

-1

0

1

2

3

4

5

0.70

0.65

0.60

0.550.50

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 in drag due to C.G.

depends on airplane design, weight,

altitude and Mach

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

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

38Fuel Conservation

Definition of Optimum Altitude

FUEL MILEAGE (NAM/LB)

PRES

SUR

E A

LTIT

UD

E (1

000

FT)

0.024 0.028 0.032 0.036 0.040 0.044 0.04830

32

34

36

38

40

GROSS WT(1000 LB)

620

580

540

500

460 420 380 340300

OPTIMUM

(CONSTANT MACH NUMBER)

Pressure Altitude Which Provides the Maximum Fuel Mileage for a Given Weight and Speed

39Fuel Conservation

LRC Mach

Determining Optimum Altitude

Cruise weight (1000 KG)

Brake release weight (1000 KG)

45

40

35

30 70 60 90 80 110 100 120

70 80 90 100 100 120

Pressure altitude (1000 ft)

40Fuel Conservation

Step Climb

= Off optimum operations Optimum

Altitude

4000 ft

2000 ft

Stepclimb

41Fuel Conservation

Optimum altitude

+ 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 Penalty4000 ft Step vs. No Step Over a 4-Hour Cruise

(Example Only)

42Fuel Conservation

Speed Selection

NAM/pound fuel

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

Increasing weight

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

43Fuel Conservation

Speed Selection (continued)

• LRC = MRC + 1% fuel burn

• Significant speed increase for only a 1% decrease in fuel mileage

• Increases speed stability

• Minimizes throttle adjustments

LRC Versus MRC

44Fuel Conservation

0

1

2

3

4

5

6

7

8

0.00 0.01 0.02 0.03 0.04

∆ Mach from MRC

∆ Fu

el ~

%

-30

-25

-20

-15

-10

-5

00.00 0.01 0.02 0.03 0.04

∆ Mach from MRC

∆ Ti

me

~ m

in.

LRC

Model #1

Model #2

Model #2

Model #1

LRC

Mod

el #

1

LRC

Mod

el #

2

∆ Fuel For Flying Faster Than MRC

Flying Faster Than MRC?Flying faster than LRC typically produces a significant fuel

burn 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 than MRC depends on specific airplane model, weight, and altitude

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 ~ $/hrFuel cost ~ cents/lb

46Fuel Conservation

Route Selection

Choose the most favorable route available!

47Fuel Conservation

Great Circle Distance

• Shortest ground distance between 2 points on the earth’s surface

• May not be the shortest time when winds are included

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

120 min

60 min

3148

3461

Using 120 min ETOPS leads to a 9% savings in trip distance!

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?

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 1

Fuel 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)

51Fuel Conservation

Reduction in total fuel costs for multiple leg flights is usually the main reason for tankering

Reduction in total fuel costs for multiple leg flights 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?

52Fuel Conservation


• If price at departure airport is sufficiently less than at the destination airport, surplus fuel could be carried from the 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 (often called ‘surplus fuel burn-off’)

• Surplus fuel burn-off must be accounted for in any price differential calculation

• To be cost-effective, the difference in fuel price between the departure and destination airports must be large enough to offset the cost of the additional fuel burned in carrying the tankered fuel

Fuel Price Differential

53Fuel 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 when loading extra fuel for tankering!

Limitations On Total Amounts

54Fuel 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 overweight landing could result

• Higher maintenance costs: engines, reversers, wheels, tires, brakes

Additional Considerations

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 the requirements of your operations. (e.g., If the decision to tanker is made by the captain at the time 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

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

57Fuel Conservation

Cost Calculations (continued)

• All methods should begin by checking whether takeoff and landing weight limits, along with fuel capacity limits, allow additional fuel to be loaded

• Some operators choose a minimum tankeringamount such that if the amount available to tanker is not at least equal to their chosen minimum, no fuel will be tankered

58Fuel Conservation

Cost Calculations (continued)

Calculation of fuel prices is not always as easy as 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 (affects

price per gallon - as more fuel is purchased, the hookup price/gallon decreases)

• Taxes charged may be returned later as tax rebates lower the price per gallon

59Fuel Conservation

‘Assumed Percentage Burn-off’ Method

• Assumes a fixed percentage of the tankered fuel is consumed per hour of flight time; usually 4 to 5% per hour

• Divide total cost of additional fuel purchased at departure airport by amount remaining at destination 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 the allowance for unknown costs

• If price of fuel at destination is above the breakeven price, then it is cost-effective to tanker

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

61Fuel Conservation

Trip distance (nm) Break-even price ratio

200400600800

100020003000400050006000

1.0121.0231.0341.0461.0611.1301.2171.3341.4951.722

Sample

data only

varie

s with

airp

lane m

odel

Sample

data only

varie

s with

airp

lane m

odel

• To economically justify tanker operation, the fuel price at the destination must be greater than the break-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

62Fuel Conservation

$ * (tankered fuel) = $ * (tankered fuel - fuel burnoff)gal gal

Orig Dest = tankered fuelremaining at dest

Break-evenprice ratioOrig

$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 the cost of purchasing the fuel at the destination is equivalent to the cost of purchasing the same amount of fuel, plus the fuel required to carry it, at the origin

• Break-even price occurs when:

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 any allowance for additional maintenance costs; it only considers the extra fuel burn off

64Fuel Conservation

Example Cost Calculation

Fuel price at origin: $0.80/galModel: 737-700/CFM56-7B24

Trip distance: 2000 NM

Trip distance, nm Break-even price ratio200400600800

1000200030004000

1.0151.0311.0451.0591.0751.1751.3111.477

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)

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 not tankering fuel

• Requires calculation of fuel required for actual routes with and without tankering

66Fuel Conservation

A B C

Leg 1 Leg 2

galA

$ Fuelreq’dleg 1

Fuelcarriedfor usein leg 2

+Extra fuelburned on

leg 1 due toextra wt

+ +Additional

incrementalcosts due tohigher weight gal

B

$+

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)

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

+additional

incrementalcosts due tohigher weight

- *gal

A

$fuel

carriedfor usein leg 2


Relative cost to tanker =

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 below which there will not be tankering. (e.g., if minimum gain selected as $100, then tankering will only be used if relative cost to tanker < - $100)

• Multiple legs (3 or more) add significantly to the complexity of the analysis


69Fuel Conservation

Additional Applications

• If fuel is tankered in order to obtain a shorter turnaround time at a given destination you can determine the relative 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


70Fuel Conservation

Fuel Tankering

• Most flight planning services offer tankeringanalyses to their customers

• You can work with your flight planning service on which assumptions to use/include, and in what form the results should be reported

71Fuel Conservation

Flight Crew

Opportunities for Fuel Conservation:• Practice fuel economy in each phase of flight• Understand the airplane’s systems - Systems

Management

72Fuel Conservation

Engine Start

• Start engines as late as possible, coordinate with ATC departure schedule

• Take delays at the gate if possible

• Minimize APU use if ground power available

73Fuel Conservation

Taxi

• Take shortest route possible

• Use minimum thrust and minimum braking

• Taxi with all engines operating?

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:

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

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 in the long-term, total costs will be reduced by using reduced takeoff thrust)

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)

∆TS

FC @

100

0 cy

cles

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)

Reduced Take Off ThrustImproves Long-term Performance Retention

78Fuel Conservation

Distance

Altitude

Initial cruise altitude

Cost indexincreasing

A

BCI

= 0

(M

in fu

el)

Min time to Point B

Max

gra

dien

t

Climb

Cost Index = 0 minimizes fuel to climb and cruise to a common point in space

79Fuel Conservation

Cruise

• A plane flying in steady, level flight may require some control surface inputs to maintain lateral-directional control

• Use of the proper trim procedure minimizes drag

• Poor trim procedure can result in a 0.5% cruise drag penalty on a 747

• Follow the procedures provided in the Flight Crew Training Manual

Lateral - Directional Trim Procedure

80Fuel Conservation

Systems ManagementCruise

• 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

81Fuel Conservation

WindsCruise

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

• Want to maximize ground miles per unit of fuel burned

• Wind-Altitude trade tables are provided in the flight crew operations manual

82Fuel Conservation

Fuel Mileage = =Fuel Flow

VTAS

KGNAM

Fuel Used = =NGM/KG

NGM

NAM/KG

NAM=

VTAS + VWIND

(NGM) (Fuel Flow)

Ground Fuel Mileage = =Fuel Flow

VTAS + VWIND

KGNGM

In cruise: positive wind = Tailwindnegative wind = Headwind

VGround

Wind Effects On Fuel Mileage

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 to FL350 to obtain equivalent

ground fuel mileage

84Fuel Conservation

MACH number

Gro

und

fuel

mile

age

.80 .81 .82 .83 .84 .85 .8664

66

68

70

72

74

76

78

35K, Wind = 0

31K, Wind = 0

MACH number

Gro

und

fuel

mile

age

.80 .81 .82 .83 .84 .85 .8664

66

68

70

72

74

76

78

35K, Wind = 0

31K, Wind = 0

Wind = 10

Wind = 20

Wind = 30

Wind = 40

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

Wind = -10

Wind = -20

Wind = -30

Wind = -40

Wind Effects On Cruise Altitude: Wind/Alt Trade

* Actual ground fuel mileage comparisons vary with airplane model, weight, and altitudes considered

85Fuel Conservation

Gro

und

fuel

mile

age

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

MRC

LRC

Typical affect of wind on ground fuel mileage when flying 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

86Fuel Conservation

Descent

• Penalty for early descent - spend more time at low altitudes, 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)

87Fuel Conservation

Distance

Final cruise altitude

Cost indexincreasing

B

CI = 0 (Min fuel)

Min tim

e from point A to B

Descent

Cost Index = 0 minimizes fuel between a common cruise point and a common end of descent point

Altitude

A

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Approach

• Do not transition to the landing configuration too early

• Fuel flow in the landing configuration is approximately 150% of the fuel flow in the clean configuration

89Fuel Conservation

Summary Of Operational Practices

• 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

90Fuel Conservation

Flight CrewsSummary Of Operational Practices

• 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 for Fuel Conservation

92Fuel Conservation

Opportunities For Fuel ConservationMaintenance Personnel

• Airframe maintenance

• Engine maintenance

• Systems maintenance

93Fuel Conservation

Excess Drag Is Lost Payload

94Fuel Conservation

Excess Drag Means Wasted FuelExcess Drag Means Wasted Fuel

• 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.

95Fuel Conservation

Total Drag Is Composed Of:

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

96Fuel Conservation

Drag due to airplane size and weight (unavoidable)

~ 90%

Pressure, trim and interference drag (optimized in the wind tunnel)

~ 6%

Excrescence drag (this can increase)

~ 4%

Contributors To Total Airplane Drag(New Airplane at Cruise Conditions)

* Typical values for illustration purposes. Actual magnitudes vary with airplane model

97Fuel Conservation

What Is Excrescence Drag?

The additional drag on the airplane due to the sum of all deviations from asmooth sealed external surface

Proper maintenance can prevent an increase in excrescence drag

98Fuel Conservation

0

1

2

3

4

Excrescence drag(% airplane drag)

Discrete items

Mismatches and gaps

Internal airflow & seal leakage

Roughness & surface irregularities

Excrescence Drag On A ‘New Airplane’ Is Composed Of:

Total

* Typical values for illustration purposes. Actual magnitudes vary with airplane model

99Fuel Conservation

Discrete Items

• Antennas, masts, lights

• Drag is a function of design, size, position

100Fuel Conservation

Mismatched Surfaces

Steps and gaps at skin joints, around windows, doors, control surfaces, and access panels

Frame

Skin


Internal Airflow

Leaks from higher to lower pressure areas due to

deteriorated or poorly-installed aerodynamic 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

• Forward portion of fuselage and nacelle

• Leading areas of wings and tail

• Local Coefficient of Pressure (Cp) is highest

All spoilers up3.75” = 2% drag

Outboard aileron up4” = 1% drag

Rudder deflection 4.5 degrees(offset 9.5” at base) =2% drag

1” tall ridge on wing75 ft. long = 2% drag

747 Cruise Drag Sensitivities747 Cruise Drag Sensitivities


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 largeincrease 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 Can be Easily Made

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


Misrigged Ailerons

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


Spoilers

The spoilers can begin to rise if the aircraft is balanced 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)


Misalignment, Mismatch

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

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 step

Airflow


Positive Step and Improper Seal

727 surface mismatch - lower wing critical area(flap track fairing - fabricated leather seal) - positive step

Airflow


Check for Tight Aircraft Doors

Note the tight and even fit of the air conditioning 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

Passenger doors

Fwd cargo door seal depressor

before repair


Check for Missing or Damaged Seals

747 R.H. Wing gear well door forward outboard seal missing and damaged

Airflow


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 exterior is beneficial– 0.1% drag reduction if

excessively dirty– Minimizes metal corrosion

and paint damage– Location of leaks and local

damage

• Customer aesthetics


Make Simple Inspections

• 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

• 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

• Operating empty weight (OEW) typically increases 0.1% to 0.2% per year, leveling off around +1% from a new-airplane level in 5 to 10 years

• Most OEW growth is mainly due to accumulation of:– Moisture– Dirt


Engine Maintenance

• Need to balance savings from performance improvements versus cost to perform maintenance

• Maintenance performed on high and low pressure turbines and compressors will help keep fuel consumption from deteriorating


Items That Cause Engine/Fuel Burn deterioration

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 The Environment In Which They Operate


Typical Engine Deterioration Mechanisms

Increased tip clearances

Seal leakage

Airfoil erosion

Dirt accumulation



Scheduled Refurbishing Recovers SFC and EGT


SFC or

EGT

Hours or cycles

Shop visit

Shop visit


Simple Procedures Can Recover Performance Between Scheduled Shop Visits

On-Wing Engine Washing• Addresses dirt accumulation

On-Wing Engine Bleed Rigging• Addresses leakage caused by bleed

system wear



On-Wing Engine Washing

• Simple procedure• Special tooling identified• 3-4 hours, two mechanics

Up to 1.5% SFC improvements

possible

Hand wash fan and LPC stator vanes

Regular Intervals Ensure Fuel Economy



0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 1000 2000 3000 4000 5000 6000Cycles

% ∆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

SFC and EGT Can Be Recovered Between Shop Visits Using Repetitive Engine Washes



On-Wing Engine Bleed Rigging

• Simple procedure

• Start, stability, service bleeds

• Problem Identified from in-flight performance trends

Up to 2.5% SFC benefit possible

Repair of Leaking Bleed Valves Saves Fuel



Instrument Calibration

• 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 the 747-400, flying 0.01M faster can increase fuel burn by 1% or more


Airspeed System Error Penalty

• Keep airspeed system calibrated

• Airspeed reads 1% low, airplane flies 1% fast

• About 2% drag penalty in a 747


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.

Check Static Sources


Don’t let this… Don’t let this…

Become this!Become this!

Proper and Continuous Airframe and Engine Maintenance Will Keep Your Airplanes Performing at Their Best!


It Takes the Whole Team to WinConclusions

• Large fuel savings results from the accumulation of 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 and requirements


For More Information

• 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 1984

to 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 fuel conservation over the last 4 decades in the following publications:

End ofFuel Conservation

Flight Operations EngineeringBoeing Commercial Airplanes

November 2004

Fuel Conservation

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