Originally Posted by
MD83FO
the question that arrises now is, what constitutes a proper alignment, when i did the type rating in 2004, the FCOM 4 stated that all 3 IRSs should be turned on simultaneously for an ideal alignment and the from/to inserted as soon as the IRS's were switched on to minimize drift
You are correct, if you reset one ADIR at a time you will damage the RTLU because even if you reset one at a time you still ganna have the FAC 1+2 fault on the ecam, and thats the problem. FAC supply the RTLU in therms of air speed, and once they have lack of information, the Emergency Return to low speed mode will activate. But as far as i could find, this problems only will happen if you perform a Full Alignment, when a Fast Alignment is performed, a Battery Clock ensures that the FAC will not be without speed data during those 5 seconds.