getting to grips with aircraft performance 如何掌握飞机性能 1(23)

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 Accelerate from VEF to V11 assuming the critical engine fails at VEF and the pilot takes the first action to reject the takeoff at V1

-Come to a full stop23
- Plus a distance equivalent to 2 seconds at constant4 V1 speed
1 Delay between VEF and V1 = 1 second
2 ASD must be established with the “wheel brakes at the fully worn limit of their allowable wear  range”

  [JAR/FAR 25.101]
3 ASD shall not be determined with reverse thrust on a dry runway
4 Pre-amendment 42 : no additional distance

  Amendment 25-42 : 2 seconds of continuing acceleration after V1

. ASDN dry = Sum of the distances necessary to:
- Accelerate the airplane with all engines operating to V1, assuming the pilot takes the first action to reject the takeoff at V1
-With all engines still operating come to a full stop
- Plus a distance equivalent to 2 seconds at constant V1 speed
ASDdry = max of {ASDN-1 dry, ASDN dry}
b) The accelerate-stop distance on a wet runway is the greater of the following values:
.
ASDdry

.
ASDN-1 wet = same definition as ASDN-1 dry except the runway is wet1

.
ASDN wet = same definition as ASDN dry except the runway is wet

1 ASD determination on a wet runway may include the use of the reverse thrust provided it is safe and reliable [JAR/FAR 25-109 (e)(f)]

3.1.5. Influence of V1 on Accelerate-Go/Stop Distances
For a given takeoff weight, any increase in V1 leads to a reduction in both TODN-1 and TORN-1. The reason is that the all engine acceleration phase is longer with a higher V1 speed, and, consequently, in case of an engine failure occurring at VEF, the same V2 speed can be achieved at 35 feet at a shorter distance.
On the other hand, TODN and TORN are independent of V1 as there is no engine failure, and thus no consequence on the acceleration phase and the necessary distance to reach 35 feet.
On the contrary, for a given takeoff weight, any increase in V1 leads to an increase in both the ASDN-1 and ASDN. Indeed, with a higher V1 speed, the acceleration segment from brake release to V1 is longer, the deceleration segment from V1 to the complete stop is longer, and the 2 second segment at constant V1 speed is longer.
As a result, the following graph providing the takeoff/rejected takeoff distances as a function of V1 can be plotted. This graph clearly shows that a minimum distance is achieved at a particular V1 speed. This speed is called “balanced V1”, and the corresponding distance is called “balanced field”.

3.2. Available Takeoff Lengths
3.2.1. Takeoff Run Available (TORA)

“JAR-OPS 1.480 (a)(9) TakeOff Run Available (TORA): The length of runway which is declared available by the appropriate authority and suitable for the ground run of an aeroplane taking off.”
TORA is either equal to the runway length, or to the distance from the runway entry point (intersecting taxiway) to the end of the runway (Figure C9).
　
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