To summarize, NPA 244 and NPRM 93-08 (post-amendment 42) proposed the following rule changes: 1 – Replace the two seconds of continued acceleration beyond V1, with a distance margin equal to two seconds at V1 speed 2 – Require that the runway surface condition (dry or wet) be taken into account, when determining the runway length that must be available for takeoff. 3 – Require that the capability of the brakes to absorb energy and stop the airplane during landings and rejected takeoffs be based on brakes that are worn to their overhaul limit. 

After industry feedback, NPA 244 was incorporated into JAR 25 on October 2000 (change 15), whereas NPRM 93-08 was incorporated into FAR 25 on February 1998 (amendment 25-92). The definitions provided in the following sections refer to the latest airworthiness standards (i.e. post amendment 42). 

As a reminder, the certification status of the Airbus models is the following: 

. Pre-amendment 42  : A300, A300-600, A310  

. Amendment 25-42  : A3201  

. Post-amendment 42  : A318, A319, A3201, A321, A330, A340  

3.1.2. Takeoff Distance (TOD) 

For given operational conditions (temperature, pressure altitude, weight, etc.): 

a) The takeoff distance on a dry runway is the greater of the following values: 

. TODN-1 dry = Distance covered from the brake release to a point at which the aircraft is at 35 feet above the takeoff surface, assuming the failure of the critical engine at VEF and recognized at V1, 

. 1.15 TODN dry = 115% of the distance covered from brake release to a point at which the aircraft is at 35 feet above the takeoff surface, assuming all engines operating. 

1 Some A320s are certified with amendment 25-42, others with post-amendment 42. 

TODdry = max of {TODN-1 dry, 1.15 TODN dry} 

b)  The takeoff distance on a wet runway is the greater of the following values: 

. TODdry = Takeoff distance on a dry runway (see above), 

. TODN-1 wet = Distance covered from brake release to a point at which the aircraft is at 15 feet above the takeoff surface, ensuring the V2 speed to be achieved before the airplane is 35 feet above the takeoff surface, assuming failure of the critical engine at VEF and recognized at V1. 

3.1.3. Takeoff Run (TOR) 

3.1.3.1. Runway with Clearway 

a) The takeoff run on a dry runway is the greater of the following values (Figure C6): 

. TORN-1 dry = Distance covered from brake release to a point equidistant between the point at which VLOF is reached and the point at which the aircraft is 35 feet above the takeoff surface, assuming failure of the critical engine at VEF and recognized at V1, 

. 1.15 TORN dry = 115 % of the distance covered from brake release to a point equidistant between the point at which VLOF is reached and the point at which the aircraft is 35 feet above the takeoff surface, assuming all engines operating. 

TORdry = max of {TORN-1 dry, 1.15 TORN dry} 

b) The takeoff run on a wet runway is the greater of the following values: 

. TORN-1 wet = Distance covered from the brake release to a point at which the aircraft is at 15ft above the takeoff surface, ensuring the V2 speed to be achieved before the airplane is 35 feet above the takeoff surface, assuming the failure of the critical engine at VEF and recognized at V1. It is equal to TODN-1 wet . 

3.1.3.2. Runway without Clearway 

The takeoff run is equal to the takeoff distance, whatever the takeoff surface (dry or wet). 

3.1.3.3. Clearway Influence on a Wet Runway 

With a wet runway, the takeoff run with one engine-out is always equal to the takeoff distance with one engine-out (i.e. from brake release to 15 feet). Therefore, a clearway does not give any performance benefit on a wet runway, as the TOR is always more limiting (TORA less than TODA). 

3.1.4. Accelerate-Stop Distance (ASD) 

a) The accelerate-stop distance on a dry runway is the greater of the following values: 

. ASDN-1 dry = Sum of the distances necessary to: 

- Accelerate the airplane with all engines operating to VEF, 

- 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