getting to grips with aircraft performance 如何掌握飞机性能 1(18)

-
 The Climb (CL) thrust represents the maximum thrust available during the climb phase to the cruise flight level. Note that the maximum climb thrust is greater than the maximum cruise thrust available during the cruise phase.

5.2. Takeoff Thrust Limitations
Figure B11 shows the influence of pressure altitude and outside air temperature on the maximum takeoff thrust, for a given engine type.
At a given pressure altitude, temperature has no influence on engine takeoff thrust, below the so-called reference temperature (Tref) or flat rating temperature. Above this reference temperature, engine thrust is limited by the Exhaust Gas Temperature (EGT). The consequence is that the available thrust decreases as the temperature increases.
On the other hand, at a given temperature, any increase in the pressure altitude leads to decreasing the available takeoff thrust.

C. TAKEOFF
1. INTRODUCTION
The possibility of engine failure during takeoff should always be considered, and the crew must be provided with the appropriate means of deciding on the safest procedure in the event of such a failure.

During the takeoff phase, the pilot must achieve the sufficient speed and angle of attack conditions to balance the aircraft’s lift and weight forces.
At the end of the ground acceleration phase, the pilot pulls the stick to start the rotation. During this phase, acceleration is maintained and the angle of attack is increased in order to achieve a higher lift. The ground reactions progressively decrease until lift off.
As mentioned above, the performance determination must take into account the possibility of an engine failure during the ground acceleration phase. For FAR/JAR certified aircraft, failure of the most critical engine must be considered.

“JAR/FAR 1.1 : 'Critical Engine' means the engine whose failure would most adversely affect the performance or handling qualities of an aircraft”, i.e. an outer engine on a four engine aircraft.

2. TAKEOFF SPEEDS
2.1. Operational Takeoff Speeds
2.1.1. Engine Failure Speed: VEF

“JAR/FAR 25.107
(a)(1) VEF is the calibrated airspeed at which the critical engine is assumed to fail.
VEF must be selected by the applicant, but may not be less than VMCG.”

2.1.2. Decision Speed: V1

V1 is the maximum speed at which the crew can decide to reject the takeoff, and is ensured to stop the aircraft within the limits of the runway.
“JAR/FAR 25.107 (a)(2) V1, in terms of calibrated airspeed, is selected by the applicant; however, V1 may not be less than VEF plus the speed gained with the critical engine inoperative during the time interval between the instant at which the critical engine is failed, and the instant at which the pilot recognises and reacts to the engine failure, as indicated by the pilot's initiation of the first action (e.g. applying brakes, reducing thrust, deploying speed brakes) to stop the aeroplane during accelerate-stop tests.”
　
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：getting to grips with aircraft performance 如何掌握飞机性能 1(18)