getting to grips with aircraft performance 如何掌握飞机性能 1(20)

Table C1: VLOF Limitation
2.1.5. Takeoff Climb Speed: V2

V2 is the minimum climb speed that must be reached at a height of 35 feet above the runway surface, in case of an engine failure.
“JAR/FAR 25.107
(b)
 V2min, in terms of calibrated airspeed, may not be less than:

.  
1.13 VSR1 (JAR) or 1.2 VS (FAR) for turbo-jet powered aeroplanes […]

.  
1.10 times VMCA

(c)
 V2, in terms of calibrated airspeed, must be selected by the applicant to provide at least the gradient of climb required by JAR 25.121(b) but may not be less than:

.  
V2min; and

.  
VR plus the speed increment attained before reaching a height of 35 ft above the take-off surface.”

This speed must be entered by the crew during flight preparation, and is represented by a magenta triangle on the speed scale (see Figure C3).
V2 ≥ 1.1 VMCA V2 ≥ 1.13 Vs1g (Airbus Fly-By-Wire aircraft)2
 V2 ≥ 1.2 Vs     (Other Airbus types)
1 VSR is the 1-g stall speed VS1g (refer to the “Aircraft limitations” chapter).
2 Airbus FBW aircraft are FAA approved, under special condition, with the 1-g reference stall speed.

2.2. Takeoff Speed Limits
2.2.1. Maximum Brake Energy Speed: VMBE
When the takeoff is aborted, brakes must absorb and dissipate the heat corresponding to the aircraft’s kinetic energy at the decision point (1/2.TOW.V12).

“JAR/FAR 25.109
(h) A flight test demonstration of the maximum brake kinetic energy accelerate-stop distance must be conducted with no more than 10% of the allowable brake wear range remaining on each of the aeroplane wheel brakes.”
Brakes have a maximum absorption capacity, known as maximum brake energy. For certification purposes, this absorption capacity must be demonstrated with worn brakes (post-amendment 42 only). As a result, the speed at which a full stop can be achieved for a given takeoff weight is limited to a maximum value (VMBE). Thus, for a given takeoff weight:

2.2.2. Maximum Tire Speed: VTIRE
The tire manufacturer specifies the maximum ground speed that can be reached, in order to limit the centrifugal forces and the heat elevation that may damage the tire structure. Thus:

For almost all Airbus aircraft models, VTIRE is equal to 195 knots (Ground Speed).
2.3. Speed Summary
The following Figure illustrates the relationships and the regulatory margins between the certified speeds (VS1G, VMCG, VMCA, VMU, VMBE, VTIRE), and the takeoff operating speeds (V1, VR, VLOF, V2).

3. RUNWAY LIMITATIONS
3.1. Takeoff Distances
3.1.1. Regulatory Background
The different Airbus types have been certified at different times and comply with different certification rules. A major change occurred when the FAA published an amendment to FAR Part 25, known as “Amendment 25-42”. This amendment, which became effective on March 1, 1978, revised the takeoff performance standards and made them more restrictive.
　
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(20)