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The different Airbus types have been certified at different times and comply with different certification rules.
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A major change occurred when the FAA published an amendment to FAR Part 25, known as "๐๐ฆ๐๐ง๐๐ฆ๐๐ง๐ญ ๐๐-๐๐".
This amendment, which became effective on March 1, 1978, revised the takeoff performance standards and made them more restrictive.
Amendment 25-42 required accelerate-stop distance to include ๐ ๐ฌ๐๐๐จ๐ง๐๐ฌ ๐จ๐ ๐๐จ๐ง๐ญ๐ข๐ง๐ฎ๐๐ ๐๐๐๐๐ฅ๐๐ซ๐๐ญ๐ข๐จ๐ง ๐๐๐ฒ๐จ๐ง๐ ๐๐ ๐ฌ๐ฉ๐๐๐, before the pilot takes any action to stop the airplane.
It also introduced the ๐๐๐๐๐ฅ๐๐ซ๐๐ญ๐-๐๐ญ๐จ๐ฉ ๐๐ข๐ฌ๐ญ๐๐ง๐๐ ๐๐ฅ๐ฅ ๐๐ง๐ ๐ข๐ง๐๐ฌ.
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 Airbus #A320 was the first airplane to be certified under this rule, as no retroactivity was required.
And it was the last one too.
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 type-certified to the standards introduced by Amendment 25-42 were penalized in terms of payload, even though the 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 created an unfair international trade situation, affecting the competitiveness of a later design of the A320.
At the June 1990 annual meeting, the FAA & 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.
NPA 244 and NPRM 93-08 (post-amendment 42) proposed the following rule changes:
โข Replace the two seconds of continued acceleration beyond V1, with a distance margin equal to two seconds at V1 speed.
โข Require that the runway surface condition (dry or wet) be taken into account, when determining the runway length that must be available for takeoff.
โข 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 certification status of Airbus models is as follows:
โข Pre-amendment 42 : A300, A300-600, A310
โข Amendment 25-42 : A320*
โข Post-amendment 42 : A318, A319, A320*, A321, A330, A340, A380, A350
*Some A320โs are certified with amendment 25-42, others with post-amendment 42