Download This Article (PDF - 184 KB)Comparing the fuel usage of two standard climb profiles
Figure 2 shows two standard climb profiles for each airplane. These simplified profiles are based on the International Civil Aviation Organization (ICAO) Procedures for Air Navigation Services Aircraft Operations (PANS-OPS) Noise Abatement Departure Procedures (NADP) NADP 1 and NADP 2 profiles. Profile 1 is a climb with acceleration and flap retraction beginning at 3,000 feet (914 meters) AGL, which is the noise climb-out procedure for close-in noise monitors. Profile 2 is a climb with acceleration to flap retraction speed beginning at 1,000 feet (305 meters) AGL, which is the noise climb-out procedure for far-out noise monitors. As a general rule, when airplanes fly Profile 2, they use 3 to 4 percent less fuel than when flying Profile 1.
FUEL-SAVING POTENTIAL OF TWO CLIMB PROFILES
Figure 2
| Airplane Model |
Takeoff Gross Weight Pounds (kilograms) |
Profile Type |
Takeoff Flap Setting |
Fuel Used Pounds (kilograms) |
Fuel Differential Pounds (kilograms) |
| 717-200 | 113,000 (51,256) |
1 |
13 |
4,025 (1,826) |
- |
2 |
3,880 (1,760) |
145 (66) |
|||
| 737-800 Winglets | 160,000 (72,575) |
1 |
10 |
5,234 (2,374) |
- |
2 |
5,086 (2,307) |
148 (67) |
|||
| 777-200 Extended Range |
555,000 (249,476) |
1 |
15 |
14,513 (6,583) |
- |
2 |
14,078 (6,386) |
435 (197) |
|||
| 747-400 | 725,000 (328,855) |
1 |
10 |
21,052 (9,549) |
- |
2 |
20,532 (9,313) |
520 (236) |
|||
| 747-400 Freighter | 790,000 (358,338) |
1 |
10 |
23,081 (10,469) |
- |
2 |
22,472 (10,193) |
609 (276) |
Figure 3 shows the combined effect of using a lower takeoff flap setting and flying Profile 2, compared to using a higher takeoff flap setting and flying Profile 1. Combining a lower takeoff flap setting with Profile 2 saves approximately 4 to 5 percent fuel compared to the higher takeoff flap setting and Profile 1.
EFFECT OF COMBINING TAKEOFF AND CLIMB STRATEGIES
Figure 3
| Airplane Model |
Takeoff Gross Weight Pounds (kilograms) |
Profile Type |
Takeoff Flap Setting |
Fuel Used Pounds (kilograms) |
Fuel Differential Pounds (kilograms) |
| 717-200 | 113,000 (51,256) |
1 |
18 |
4,061 (1,842) |
- |
2 |
5 |
3,859 (1,750) |
202 (92) |
||
| 737-800 Winglets | 160,000 (72,575) |
1 |
15 |
5,273 (2,392) |
- |
2 |
5 |
5,069 (2,299) |
204 (93) |
||
| 777-200 Extended Range |
555,000 (249,476) |
1 |
20 |
14,710 (6,672) |
- |
2 |
5 |
14,018 (6,358) |
692 (314) |
||
| 747-400 | 725,000 (328,855) |
1 |
20 |
21,419 (9,715) |
- |
2 |
10 |
20,532 (9,313) |
887 (403) |
||
| 747-400 Freighter | 790,000 (358,338) |
1 |
20 |
23,558 (10,686) |
- |
2 |
10 |
22,472 (10,193) |
1,086 (493) |
Once the flaps are retracted, the crew should accelerate to maximum rate of climb speed. The 737s with flight management computers (FMC) provide this speed directly via the FMC control display unit. All Boeing flight crew training manuals provide guidance for maximum rate of climb speed. It can also be achieved by entering a cost index of zero in the FMC. (See “Cost Index Explained” in the second-quarter 2007 AERO.)
Other considerations
From a fuel consumption perspective, a full-thrust takeoff and a full-thrust climb profile offer the most fuel economy for an unrestricted climb. However, from an airline’s cost perspective, this must be balanced with engine degradation and time between overhauls, as well as guidance from the engine manufacturer. The airline’s engineering department must perform the analysis and provide direction to flight crews to minimize overall cost of operation when using takeoff derates or assumed temperature takeoffs and climbs.
Summary
In a time when airlines are scrutinizing every aspect of flight to locate possible opportunities to save fuel, the takeoff and climb phases of flight should be considered as part of an overall fuel savings effort. The impact of incorporating fuel saving strategies into every phase of the operation can result in considerable cost reductions.
Boeing Flight Operations Engineering assists airlines’ flight operations departments in determining appropriate takeoff and climb profiles specific to their airplane models. For more information, please contact FlightOps.Engineering@boeing.com.
The role of the flight crew in fuel conservation
Every area of an airline has a part to play in reducing the cost of the operation. But the flight crew has the most direct role in cutting the amount of fuel used on any given flight.
The flight crew has opportunities to affect the amount of fuel used in every phase of flight without compromising safety. These phases include planning, ground operations, taxi out, takeoff, climb, cruise, descent, approach, landing, taxi in, and maintenance debrief.
Top fuel conservation strategies for flight crews include:
- Take only the fuel you need.
- Minimize the use of the auxiliary power unit.
- Taxi as efficiently as possible.
- Take off and climb efficiently.
- Fly the airplane with minimal drag.
- Choose routing carefully.
- Strive to maintain optimum altitude.
- Fly the proper cruise speed.
- Descend at the appropriate point.
- Configure in a timely manner.
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