Originally Posted by Bubi352
It's apparently a function of AGL not MSL. I was told if you were on an ILS above 8,000 AGL and were to arm the approach on the FCU, the autopilot would disengage and the FDs disappear.
All I can read in the FCOM 4 is the following :
But maybe not the best procedure to arm an ILS too early as spurious or false capture for LOC and/or G/S may occur.
RNAV is a different matter, and I can remember arming RNAV approach well above 10000 feet with no adverse consequence.