Originally Posted by
AerocatS2A
Doesn’t the Boeing FLCH put the autothrottles in HOLD mode during descent? Then the pilot can manually adjust thrust to adjust descent rate. The Airbus open descent doesn’t do that, if you want to adjust thrust manually in OPDES then you need to disconnect the autothrust. I haven’t flown a Boeing but have a few FCOM s and that is my understanding of the system.
Spot on!
The OPEN DES mode is a selected mode. It maintains a SPD/MACH (selected or managed) with the AP/FD pitch mode while autothrust (if active) maintains IDLE thrust. It is not to be used for final approach.
The OPEN DES mode can be engaged only if the following conditions are met: ‐ The aircraft has been in flight for more than 5 s ‐ LAND mode is not engaged ‐ The FCU selected altitude is lower than present altitude. The OPEN DES mode is engaged by one of the following: ‐ Pulling out the ALT knob ‐ Selecting a manual speed when EXP mode is engaged. Note: When OP DES is engaged: ‐ The FMA displays “OP DES” ‐ The managed LVL/CH dot on the FCU goes out ‐ The system arms the ALT mode.
The OPEN DES mode is disengaged by one of the following conditions: ‐ Manual engagement of another vertical mode ‐ Selection of an altitude higher than present altitude. V/S (FPA) engages on current V/S (FPA). The vertical mode is boxed white. If within 5 s after the reversion to V/S, the flight crew does not confirm the altitude target change by another expected action, a triple click aural warning sounds, and the V/S (FPA) is boxed white and flashes for 10 s.
When OPEN DES is engaged, pitch control maintains the target speed/Mach number, and autothrust maintains idle thrust (or the flight crew maintains it manually). The speed target may be either selected or managed. The OPEN DES mode disregards all altitude constraints.