Chris
The moral is: on the A320 NEVER disobey the FD pitch bar in OP DES mode, particularly if you are relying on A/THR to control speed (it won't, because it will be in IDLE mode)."
"After the Bangalore accident, the FMGS logic was modified to switch automatically from OP DES mode to VS mode when the IAS fell much below VLS. (can't remember the figure right now). When the FMGS switches to VS mode, the A/THR mode changes from IDLE to SPD."
Isn't that basic? Open des or des means only pitch will maintain speed. If you are manual and you ignore FDs and drop speed at Vls-2 FDs will go off and managed descent speed will change to select speed and ATHR will change to speed mode to capture that speed. No Chris FDs don't change to VS mode only ATHR changes to speed.
Last edited by vilas; 19th December 2013 at 09:55.