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“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. 

To summarize, Amendment 25-42 required the accelerate-stop distance to include two seconds of continued acceleration beyond V1 speed, before the pilot takes any action to stop the airplane. It also introduced the notion of Accelerate-Stop Distance all engines. This revision resulted in longer accelerate-stop distances for airplanes whose application for a type certificate was made after amendment 25-42 became effective. The A320 was the first airplane to be certified under this rule, as no retroactivity was required. It was also the last one. 

Although the airplane types were originally certified at different times, thus allowing the use of different amendments, both groups of airplanes were continuing in production and competing for sales and for use over some common routes. Airplanes whose designs were type-certified to the standards introduced by Amendment 25-42 were penalized in terms of payload, even though the airplane’s takeoff performance might be better from a safety perspective, than the design of a competing airplane that was not required to meet the latest standards. 

This disparity in airworthiness standards has created an unfair international trade situation, affecting the competitiveness of a later design of the A320. At the June 1990 annual meeting, the FAA and JAA agreed to jointly review the current takeoff performance standards to reduce the above-discussed inequities, without adversely affecting safety. In March 1992, the JAA Notice for Proposed Amendment (NPA) 25B,D,G-244: “Accelerate-Stop Distances and Related Performance Matters” was issued, followed by the FAA Notice of Proposed Rule Making (NPRM) 93-8 on July 1993. The rule changes proposed in the NPA and in the NPRM were essentially the same, and are better known as Post-Amendment 42.