Hi Confiture,
Originally Posted by CONF iture
That aft fuel transfer for fuel economy is a great concept, but your figures are a bit on the optimized side. MEL mentions only 1% penalty if trim tank is disabled (no aft xfer). Nevertheless, one A330 at 6000 kg/H for 3000 FH/year is still 180 tonnes saved.
You are certainly right about that. The figure I quoted (and used for calcul) is the difference between MAC 20% and 35%. While, if I understand yours, it would certainly be for a lower difference in flight.
Nonetheless, what I posted above should also answer
Rudderrudderrat's question about the design. It seems better to have in this case a pitch Alternate rather than direct, certainly because autotrim (inop in direct law) will permanently deal with fuel transfers (the pitch law is mostly based on CG computation by fuel computers). It will also damper pitch sensitivity if CG is aft, while roll axis should be trimmed by rudder and the aircraft is supposed to fly in straight line hands off.