F D, Completing the alphabet.............
p) For APR equipped aircraft, why, under some circumstances use of APR OFF instead of APR ARMED can improve the Max Takeoff Weight? (APR fitted aircraft included to bring
Mutt in).
Think time over...........
This can occur when Accelerate-Stop limited. If the Takeoff can be accomplished for a given weight at APR OFF instead of APR ARMED the V1 is lower due to Vmcg considerations. The Net thrust up to Vef will be the same in all cases, as APR does not 'kick in' until engine failure. Vef will be reached at the same point on the runway, but as V1 is lower, accelerate-Stop is improved due to greater ASDA remaining. If APR had been armed, V1 would occur further down the runway with less ASDA remaining, thus, in an Accelerate-Stop scenario, the lower thrust rating will produce the greater RTOW.
Another consideration is that between Vef and the pilot taking 'Stop' actions, at the lesser thrust with APR OFF less runway is consumed at the lower acceleration between Vef and RTO actions..
Similar discussion applies to the use of Thrust Derates, particularly on contaminated runways.
Item q) is up for grabs...... 10 letters to go
Regards,
Old Smokey