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Boeing fuel conservation

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  • 1. Fuel Conservation Flight Operations Engineering Boeing Commercial Airplanes November 2004
  • 2. What is Fuel Conservation? Fuel conservation means managing the operation and condition of an airplane to minimize the fuel used on every flight Fuel Conservation 2
  • 3. How Much Is A 1% Reduction In Fuel Worth? Airplane type Fuel savings* 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 *Assumes typical airplane utilization rates. Actual utilization rates may differ. Fuel Conservation 3
  • 4. How Much Is This Worth In $$? Depends on Current Fuel Prices! Fuel Conservation 4
  • 5. Jet Fuel Prices $1.40 $1.20 $1.00 $/gallon $1.00 $0.80 $0.60 $0.40 $0.20 $0.00 87 89 91 93 95 97 99 01 03 Year Source: Air Transport World Fuel Conservation 5
  • 6. How Much Is A 1% Reduction In Fuel Worth? Airplane type Fuel savings* gal/year/airplane Fuel savings* $/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. Fuel Conservation 6
  • 7. 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 of Fuel Conservation 7
  • 8. How Much Is A 1% Reduction In Fuel Worth? Airplane Fuel savings* type gal/year/airplane Fuel savings* $/year/airplane Cost to Implement Total Cost Savings/AP ?? ?? 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 Total savings = fuel savings - cost to implement $30,000 → 40,000 *Assumes $1.00/gallon *Assumes typical airplane utilization rates. Actual utilization rates may differ. Fuel Conservation 8
  • 9. Saving Fuel Requires Everyone’s Help • Flight Operations • Dispatchers • Flight Crews • Maintenance • Management Fuel Conservation 9
  • 10. FLIGHT OPERATIONS ENGINEERING Operational Practices for Fuel Conservation 10
  • 11. Flight Operations / Dispatchers Opportunities For Fuel Conservation • Landing weight • Fuel reserves • Airplane loading • Flap selection • Altitude selection • Speed selection • Route selection • Fuel tankering Fuel Conservation 11
  • 12. 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) Fuel Conservation 12
  • 13. Components Of Landing Weight Fuel on board at landing WLDG Required = OEW + Payload + reserve + fuel Additional fuel loaded but not used Zero fuel weight Fuel Conservation 13
  • 14. Reducing ZFW Reduces Landing Weight Approximate % Block Fuel Savings Per 1000 Lb (454 Kg) ZFW Reduction 717-200 .9% Fuel Conservation 7377377573/4/500 6/7/8/900 200/300 .7% .6% .5% 7672/3/400 777200/300 747-400 .3% .2% .2% 14
  • 15. Reducing OEW Reduces Landing Weight Items To Consider • Passenger service items • Passenger entertainment items • Empty Cargo and baggage containers • Unneeded Emergency equipment • Excess Potable water Fuel Conservation 15
  • 16. Reducing Unnecessary Fuel Reduces Landing Weight • Practice cruise performance monitoring • Flight plan by tail numbers Fuel Conservation 16
  • 17. 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 Fuel Conservation 17
  • 18. 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 Fuel Conservation 18
  • 19. Regulatory Requirements • Is this an international flight? • FAA rules? • ICAO rules? • Other rules? Fuel Conservation 19
  • 20. FAA “International Reserves” FAR 121.645(b) A B C D (A) To fly to and land at the airport to which it is released; Contingency (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; Alternate (C) After that, to fly to and land at the most distant alternate airport specified in the flight release, if an alternate is required; and Holding (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. Fuel Conservation 20
  • 21. FAA “Island Reserves” FAR 121.645(c) • 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 Fuel Conservation 21
  • 22. ICAO International ICAO Annex 6 (4.3.6.3) C A B 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: Alternate Holding Contingency Fuel Conservation 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%). 22
  • 23. 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 Fuel Conservation 23
  • 24. 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 Fuel Conservation 24
  • 25. Speed Selection for Holding • Want to maximize time per kilogram of fuel • Use published/FMC recommended holding speeds Fuel Conservation 25
  • 26. 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 Fuel Conservation 26
  • 27. How Redispatch Works Cruise Redispatch point Climb Descent Origin Fuel Conservation Initial destination Intended destination 27
  • 28. Off Track Initial Destination Origin Initial destination Initial destination Intended destination Redispatch point Intended destination Origin Redispatch point Fuel Conservation 28
  • 29. Intent is to lower the Contingency Fuel On Board at the Final Destination Intended destination Contingency fuel g ontin C F ncy e u ed q ui r el re ncy nge red ti Con requi l Fue Reduction Redispatch point Distance (Time) Fuel Conservation 29
  • 30. Benefits of Redispatch Increased payload Reduced fuel load Fuel Conservation 30
  • 31. Examples of Using Redispatch To: 1) Increase payload 2) Decrease takeoff and landing weight (by reducing fuel load) A B C Origin Initial destination Final destination Fuel Conservation 31
  • 32. Same takeoff weight with and without redispatch TRIP FUEL Gross weight Example of payload increase with constant takeoff weight TRIP FUEL Contingency Altern + Hold Contingency Altern + Hold m nt mu poi ti Op atch isp red TRIP FUEL Altern + Hold PAYLOAD (1) PAYLOAD (2) PAYLOAD (2) OEW OEW OEW A Fuel Conservation Contingency C (No redispatch) A B B C 32
  • 33. Takeoff weight decrease TRIP FUEL TRIP FUEL Gross weight Landing weight (1) Example of takeoff weight and landing weight decreases with constant payload t oin um p tim atch Op disp re TRIP FUEL Contingency Altern + Hold Contingency Altern + Hold Altern + Hold PAYLOAD (1) PAYLOAD (2) PAYLOAD (2) OEW OEW OEW A Fuel Conservation ) t (2 )) h eig m (1 w o ing se fr nd La crea (de Contingency C (No redispatch) A B B C 33
  • 34. Airplane Loading Maintain C.G. In The Mid To Aft Range Lift wing (aft c.g.) < Lift wing (fwd c.g.) WT (fwd c.g.) = WT (aft c.g.) Lift tail (aft c.g.) Is less negative than Lift tail (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 Liftwing required to offset the WT plus the less negative Lifttail • Same Lifttotal, but lower Liftwing and therefore lower α required Fuel Conservation 34
  • 35. Airplane Loading (continued) Maintain C.G. in the Mid to Aft Range Typical trim drag increment at cruise Mach 5 4 W/δ (LB *10-6) 0.70 3 Actual variation in drag due to C.G. depends on airplane design, weight, altitude and Mach 0.65 Incremental cruise drag, % 0.60 2 0.55 0.50 1 0 -1 -2 4 Fuel Conservation 8 12 16 20 24 28 Center of gravity, %MAC 32 36 35
  • 36. 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 Fuel Conservation 36
  • 37. Altitude Selection Optimum Altitude Definition Pressure altitude for a given weight and speed schedule that produces the maximum air miles per unit of fuel Fuel Conservation 37
  • 38. Definition of Optimum Altitude Pressure Altitude Which Provides the Maximum Fuel Mileage for a Given Weight and Speed PRESSURE ALTITUDE (1000 FT) 40 GROSS WT (1000 LB) 38 460 580 380 340 300 500 540 36 420 O M TI P UM 34 620 (CONSTANT MACH NUMBER) 32 30 0.024 0.028 0.032 0.036 0.040 0.044 0.048 FUEL MILEAGE (NAM/LB) Fuel Conservation 38
  • 39. Determining Optimum Altitude 45 Pressure altitude (1000 ft) 40 LRC Mach 35 30 60 70 80 90 100 110 120 Cruise weight (1000 KG) 70 80 90 100 100 120 Brake release weight (1000 KG) Fuel Conservation 39
  • 40. Step Climb Step climb 4000 ft 2000 ft Optimum Altitude Fuel Conservation = Off optimum operations 40
  • 41. Off-Optimum Fuel Burn Penalty 4000 ft Step vs. No Step Over a 4-Hour Cruise (Example Only) + 1.5% + 0.5% + 0% + 0.5% + 1.5% 4-hour Average = + 0.6% t Op e tud alti m mu i 1000 ft 4-hour Average = + 4.8% + 1.5% Fuel Conservation + 3.0% + 4.5% + 6.5% + 8.5% 41
  • 42. Speed Selection LRC Versus MRC 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) MRC 0.12 1% LRC 0.11 MMO 0.10 NAM/ pound fuel 0.09 Increasing weight 0.08 0.07 0.06 0.05 0.60 0.64 0.68 0.72 0.76 0.80 0.84 MACH number Fuel Conservation 42
  • 43. Speed Selection (continued) LRC Versus MRC • LRC = MRC + 1% fuel burn • Significant speed increase for only a 1% decrease in fuel mileage • Increases speed stability • Minimizes throttle adjustments Fuel Conservation 43
  • 44. 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) ∆ Fuel For Flying Faster Than MRC -30 8 Model #2 Model #1 5 4 3 -20 -15 -10 2 1 -5 LRC 0 0 0.00 0.01 0.02 ∆ Mach from MRC 0.03 0.04 0.00 0.01 LRC Model #2 ∆ Fuel ~ % Model #2 Model #1 LRC Model #1 6 -25 ∆ Time ~ min. 7 ∆ Time For Flying Faster Than MRC 0.02 0.03 0.04 ∆ Mach from MRC Actual fuel burn increase, and time decrease, for flying faster than MRC depends on specific airplane model, weight, and altitude Fuel Conservation 44
  • 45. Speed Selection - Other Options • Cost Index = 0 (maximize ngm/lb = wind-adjusted MRC) • Selected Cost Index (minimize costs) Time cost ~ $/hr CI = Fuel cost ~ cents/lb • Maximum Endurance (maximize time/lb) Fuel Conservation 45
  • 46. Route Selection Choose the most favorable route available! Fuel Conservation 46
  • 47. Great Circle Distance • Shortest ground distance between 2 points on the earth’s surface • May not be the shortest time when winds are included Fuel Conservation 47
  • 48. ETOPS • ETOPS allows for more direct routes • Shorter routes = less fuel required 12 60 Iqaluit Kangerlussuaq 0 m in m in Reykjavik 346 1 Shannon Paris Goose Bay 3148 Montreal St. Johns New York Using 120 min ETOPS leads to a 9% savings in trip distance! Fuel Conservation 48
  • 49. Fuel Tankering What Is It? 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) Fuel Conservation 49
  • 50. Fuel Tankering (continued) Leg 1 Leg 2 100% tankering of 2nd leg fuel Reserves A B C No tankering of 2nd leg fuel Extra fuel burned on leg 1 to carry fuel for leg 2 Reserves Fuel loaded at A for leg 1 Fuel Conservation Fuel for leg 1 Fuel for leg 2 Fuel loaded at B for leg 2 Fuel for leg 2 Fuel for leg 1 Fuel loaded at A for legs 1 & 2 50
  • 51. Fuel Tankering (continued) Why Tanker Fuel? • Shorter turnaround time • Limited amount of fuel available • Unreliable airport services • Fuel quality at destination airport • Fuel price differential Reduction in total fuel costs for multiple leg flights is usually the main reason for tankering Fuel Conservation 51
  • 52. Fuel Tankering (continued) Fuel Price Differential • 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 tankered such 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 Conservation 52
  • 53. Fuel Tankering (continued) Limitations On Total Amounts • 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! Fuel Conservation 53
  • 54. Fuel Tankering (continued) Additional Considerations • 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 Difficult to quantify, but should be addressed in all cost calculations Fuel Conservation 54
  • 55. To Tanker or Not to Tanker Cost Calculations • 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 Fuel Conservation 55
  • 56. Cost Calculations We will briefly review 3 possible methods: 1) Assumed percentage burn-off 2) Break-even price ratio 3) Relative cost to tanker Fuel Conservation 56
  • 57. 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 tankering amount such that if the amount available to tanker is not at least equal to their chosen minimum, no fuel will be tankered Fuel Conservation 57
  • 58. 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 Fuel Conservation 58
  • 59. ‘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 Fuel Conservation 59
  • 60. 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 Fuel Conservation 60
  • 61. 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 Break-even price ratio 200 400 600 800 1000 2000 3000 4000 5000 6000 1.012 1.023 1.034 1.046 1.061 1.130 1.217 1.334 1.495 1.722 va rie Sa s w mp ith le d air ata pl o an n e ly m od el Trip distance (nm) • To economically justify tanker operation, the fuel price at the destination must be greater than the break-even fuel price Fuel Conservation 61
  • 62. 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: $ * (tankered fuel) = $ * (tankered fuel - fuel burnoff) gal gal Orig Dest $ Break-even price = gal at destination Fuel Conservation Dest B.E. = = tankered fuel remaining at dest $ gal Break-even * price ratio Orig 62
  • 63. Break-Even Price Ratio Method (continued) • If the destination fuel price is greater than the breakeven 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 Fuel Conservation 63
  • 64. Example Cost Calculation Model: 737-700/CFM56-7B24 Trip distance: 2000 NM Fuel price at origin: $0.80/gal Trip distance, nm Break-even price ratio 200 400 600 800 1000 2000 3000 4000 1.015 1.031 1.045 1.059 1.075 1.175 1.311 1.477 Break-even price = $0.80 ( 1.175) = $0.94 If dest. fuel price > $0.94, then more economical to tanker the fuel If 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) Fuel Conservation 64
  • 65. ‘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 Fuel Conservation 65
  • 66. ‘Relative Cost to Tanker’ Method (continued) Leg 1 Leg 2 A B C total cost with tankering $ gal A Extra fuel Fuel Fuel req’d + carried + burned on leg 1 due to for use leg 1 extra wt in leg 2 - $ gal * A Fuel req’d leg 1 - Additional incremental + costs due to + higher weight $ gal * B $ gal * B Additional fuel req’d for leg 2 Fuel req’d leg 2 Total cost with no tankering Fuel Conservation 66
  • 67. ‘Relative Cost to Tanker’ Method (continued) Relative cost to tanker = $ gal A fuel extra fuel carried + burned on for use leg 1 due to in leg 2 extra weight additional incremental + costs due to higher weight cost of tankering the fuel Fuel Conservation - $ gal * B fuel carried for use in leg 2 cost of purchasing at the destination 67
  • 68. ‘Relative Cost to Tanker’ Method (continued) • If relative cost to tanker = 0, then breakeven • If relative cost to tanker > 0, then costs are increased by tankering • If relative cost to tanker < 0, then costs are reduced by 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 Fuel Conservation 68
  • 69. ‘Relative Cost to Tanker’ Method (continued) 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 Fuel Conservation 69
  • 70. Fuel Tankering • Most flight planning services offer tankering analyses 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 Fuel Conservation 70
  • 71. Flight Crew Opportunities for Fuel Conservation: • Practice fuel economy in each phase of flight • Understand the airplane’s systems - Systems Management Fuel Conservation 71
  • 72. 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 Fuel Conservation 72
  • 73. Taxi • Take shortest route possible • Use minimum thrust and minimum braking • Taxi with all engines operating? Fuel Conservation 73
  • 74. Taxi One Engine Shut Down Considerations: • 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 Fuel Conservation 74
  • 75. Sample Taxi and APU Fuel Burns Condition 717 727 737 747 757 767 777 Taxi* (lb/min) 25 60 25 100 40 50 60 APU (lb/min) 4 5 4 11 4 4 9 * Assumes all engines operating during taxi Fuel Conservation 75
  • 76. 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) Fuel Conservation 76
  • 77. Reduced Take Off Thrust Improves Long-term Performance Retention 15% Average Thrust Reduction Can Improve Overall TSFC at 1000 Cycles by over 0.4% 0.0% ∆ TSFC @ 1000 cycles -0.1% Estimated Reduced Thrust Impact at 1000 Cycles -0.2% -0.3% -0.4% -0.5% -0.6% -0.7% -0.8% -0.9% -1.0% -25% (Courtesy of Pratt & Whitney) Fuel Conservation -20% -15% -10% -5% 0% Average takeoff thrust reduction (% from full rate) 77
  • 78. Climb 0 ( Min fue l) B CI = Altitude Max grad ien t Cost Index = 0 minimizes fuel to climb and cruise to a common point in space n Mi t oin P to e tim Initial cruise altitude B Cost index increasing A Distance Fuel Conservation 78
  • 79. Cruise Lateral - Directional Trim Procedure • A plane flying in steady, level flight may require some control surface inputs to maintain lateraldirectional 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 Fuel Conservation 79
  • 80. Cruise Systems Management • 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 Fuel Conservation 80
  • 81. Cruise Winds • 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 Fuel Conservation 81
  • 82. Wind Effects On Fuel Mileage Fuel Mileage = Ground Fuel Mileage = NAM KG NGM KG = = VTAS Fuel Flow VTAS + VWIND un V Gro d Fuel Flow In cruise: positive wind = Tailwind negative wind = Headwind NGM/KG = NAM NAM/KG = Fuel Used = NGM (NGM) (Fuel Flow) VTAS + VWIND Fuel Conservation 82
  • 83. Wind Effects On Cruise Altitude: Wind/Alt Trade Typical Wind/Altitude Trade Table 33 knots greater tailwind (or, lower headwind) would be required at FL310 relative to FL350 to obtain equivalent ground fuel mileage Fuel Conservation 83
  • 84. Wind Effects On Cruise Altitude: Wind/Alt Trade Typical Wind Altitude/Trade for Constant Airplane Weight Example of increasing Tailwind at 31,000 ft Example of increasing headwind at 35,000 ft 78 78 Wind = 4 0 76 Wind = 3 0 74 35K, Wind = 0 LRC, 35K Ground fuel mileage Ground fuel mileage 76 Wind = 2 0 Wind = 1 0 72 31K, Win d 70 =0 LRC, 31K 68 35K, Wind = 74 0 LRC, 35K Wind = -1 0 72 31K, Win d 70 Wind = -20 =0 Wind = -30 Wind = -4 0 68 LRC, 31K 66 66 64 .80 .81 .82 .83 .84 MACH number Fuel Conservation .85 .86 64 .80 .81 .82 .83 .84 .85 .86 MACH number * Actual ground fuel mileage comparisons vary with airplane model, weight, and altitudes considered 84
  • 85. Wind Effects On Cruise Mach Number Typical affect of wind on ground fuel mileage when flying a constant altitude and weight 220 Zero wind LRC 100 kt tailwind 200 180 Zero wind 160 C 140 100 kt headwind LRC MR Ground fuel mileage 240 120 100 200 kt headwind 80 60 .72 .73 .74 .75 .76 .77 .78 .79 .80 .81 .82 MACH number Fuel Conservation * Actual ground fuel mileage comparisons vary with airplane model, weight, and altitudes considered 85
  • 86. 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) Fuel Conservation 86
  • 87. Descent Cost Index = 0 minimizes fuel between a common cruise point and a common end of descent point A Min Final cruise altitude 0( Mi nf ue l) n poi from Altitude = e tim CI tA to B Cost index increasing B Distance Fuel Conservation 87
  • 88. 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 Fuel Conservation 88
  • 89. Summary Of Operational Practices Flight Operations / Dispatchers • 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 Fuel Conservation 89
  • 90. Summary Of Operational Practices Flight Crews • 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 Fuel Conservation 90
  • 91. Maintenance Practices for Fuel Conservation
  • 92. Maintenance Personnel Opportunities For Fuel Conservation • Airframe maintenance • Engine maintenance • Systems maintenance Fuel Conservation 92
  • 93. Excess Drag Is Lost Payload Fuel Conservation 93
  • 94. Excess Drag Means Wasted Fuel 1% Drag In Terms Of Gallons Per Year • 747 ≈ 100,000 • 777 ≈ 70,000 • 767 ≈ 30,000 • 757 ≈ 25,000 • 737 ≈ 15,000 • 727 ≈ 30,000 * Assumes typical airplane utilization rates. Actual utilization rates may differ. Fuel Conservation 94
  • 95. 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 Fuel Conservation 95
  • 96. Contributors To Total Airplane Drag (New Airplane at Cruise Conditions) Pressure, trim and interference drag (optimized in the wind tunnel) ~ 6% Fuel Conservation Excrescence drag (this can increase) ~ 4% Drag due to airplane size and weight (unavoidable) ~ 90% * Typical values for illustration purposes. Actual magnitudes vary with airplane model 96
  • 97. What Is Excrescence Drag? The additional drag on the airplane due to the sum of all deviations from a smooth sealed external surface Proper maintenance can prevent an increase in excrescence drag Fuel Conservation 97
  • 98. Excrescence Drag On A ‘New Airplane’ Is Composed Of: 4 3 Excrescence drag (% airplane drag) 2 Total Roughness & surface irregularities Internal airflow & seal leakage Mismatches and gaps 1 Discrete items 0 Fuel Conservation * Typical values for illustration purposes. Actual magnitudes vary with airplane model 98
  • 99. Discrete Items • Antennas, masts, lights • Drag is a function of design, size, position Fuel Conservation 99
  • 100. Mismatched Surfaces Steps and gaps at skin joints, around windows, doors, control surfaces, and access panels Skin Frame Fuel Conservation 100
  • 101. Internal Airflow Leaks from higher to lower pressure areas due to deteriorated or poorly-installed aerodynamic seals Airflow Fuel Conservation 101
  • 102. Roughness (Particularly Bad Near Static Sources) • Non-flush fasteners, rough surface • Waviness, gaps Non Flush Rivet Waviness Fuel Conservation Rough Surface Gaps 102
  • 103. Most Important in Critical Areas • Forward portion of fuselage and nacelle • Leading areas of wings and tail • Local Coefficient of Pressure (Cp) is highest 747 Cruise Drag Sensitivities Outboard aileron up 4” = 1% drag All spoilers up 3.75” = 2% drag Rudder deflection 4.5 degrees (offset 9.5” at base) =2% drag Fuel Conservation 1” tall ridge on wing 75 ft. long = 2% drag 103
  • 104. Regular Maintenance Minimizes Deterioration • Flight control rigging • Misalignments and mismatches • Aerodynamic seals • Exterior surface finish • OEW control • Engine maintenance • Instrument calibration Fuel Conservation 104
  • 105. Flight Control Rigging Out of rig controls and flaps can cause a large increase in fuel burn 747-400 examples: • • • • Fuel Conservation 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 105
  • 106. 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 Fuel Conservation 106
  • 107. Misrigged Ailerons Misrigged outboard ailerons can result in an increase in drag and fuel flow Fuel Conservation 107
  • 108. Spoilers The spoilers can begin to rise if the aircraft is balanced by excessive autopilot lateral input Fuel Conservation 108
  • 109. Control Surface Rigging Check 747 example (includes fit and fair check): • • • • • Fuel Conservation 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) 109
  • 110. 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 Fuel Conservation 110
  • 111. Surface Mismatch Surface Mismatch – ADF Antenna Fairing – negative step Fuel Conservation 111
  • 112. Surface Mismatch Engine inlet secondary inlet door mismatch – positive step Fuel Conservation 112
  • 113. Leading Edge Mismatch 727 surface mismatch-R.H. Wing leading edge slat actuator rod cover - positive step Fuel Conservation Airflow 113
  • 114. Positive Step and Improper Seal 727 surface mismatch - lower wing critical area (flap track fairing - fabricated leather seal) - positive step Airflow Fuel Conservation 114
  • 115. Check for Tight Aircraft Doors Note the tight and even fit of the air conditioning compartment access doors Fuel Conservation 115
  • 116. 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 Fuel Conservation Fwd cargo door seal depressor before repair 116
  • 117. Check for Missing or Damaged Seals 747 R.H. Wing gear well door forward outboard seal missing and damaged Airflow Fuel Conservation 117
  • 118. Check for Rough Surface Paint 747 rough paint - lower fuselage Airflow Fuel Conservation 118
  • 119. 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 Fuel Conservation 119
  • 120. 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 Fuel Conservation 120
  • 121. 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’ Fuel Conservation 121
  • 122. 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 Fuel Conservation 122
  • 123. 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 Fuel Conservation 123
  • 124. 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 Fuel Conservation 124
  • 125. Engine Components Are Affected By The Environment In Which They Operate Fuel Conservation 125
  • 126. Typical Engine Deterioration Mechanisms Dirt accumulation Increased tip clearances Airfoil erosion Seal leakage Fuel Conservation (Courtesy of Pratt & Whitney) 126
  • 127. Scheduled Refurbishing Recovers SFC and EGT SFC or EGT Shop visit Shop visit Hours or cycles Fuel Conservation (Courtesy of Pratt & Whitney) 127
  • 128. 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 Fuel Conservation (Courtesy of Pratt & Whitney) 128
  • 129. On-Wing Engine Washing Regular Intervals Ensure Fuel Economy • Simple procedure • Special tooling identified • 3-4 hours, two mechanics Hand wash fan and LPC stator vanes Up to 1.5% SFC improvements possible Fuel Conservation (Courtesy of Pratt & Whitney) 129
  • 130. SFC and EGT Can Be Recovered Between Shop Visits Using Repetitive Engine Washes Example of Water Wash Frequency Impact 4.0 1000 cycle wash 3.5 3.0 % ∆TSFC Unwashed 2.5 2.0 1.5 500 cycle wash 0.75% 1.0 500 cycle wash cumulative benefit 0.5 0.0 0.5% 0 1000 2000 3000 4000 Cycles Fuel Conservation (Courtesy of Pratt & Whitney) 5000 6000 1000 cycle wash cumulative benefit 130
  • 131. On-Wing Engine Bleed Rigging Repair of Leaking Bleed Valves Saves Fuel • Simple procedure • Start, stability, service bleeds • Problem Identified from in-flight performance trends Up to 2.5% SFC benefit possible Fuel Conservation (Courtesy of Pratt & Whitney) 131
  • 132. 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 Fuel Conservation 132
  • 133. Airspeed System Error Penalty • Keep airspeed system calibrated • Airspeed reads 1% low, airplane flies 1% fast • About 2% drag penalty in a 747 Fuel Conservation 133
  • 134. Check Static Sources Plugging or deforming the holes in the alternate static port can result in erroneous instrument readings in the flight deck. Keeping the circled area smooth and clean promotes aerodynamic efficiency. Fuel Conservation 134
  • 135. Proper and Continuous Airframe and Engine Maintenance Will Keep Your Airplanes Performing at Their Best! Don’t let this… Become this! Fuel Conservation 135
  • 136. Conclusions It Takes the Whole Team to Win • 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 Fuel Conservation 136
  • 137. For More Information Boeing has published numerous articles addressing fuel conservation over the last 4 decades in the following publications: • 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 Fuel Conservation 137
  • 138. End of Fuel Conservation Flight Operations Engineering Boeing Commercial Airplanes November 2004

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