Oei Airbus Operations
Thread Starter
Join Date: Mar 2004
Location: PLANET EARTH
Posts: 56
Likes: 0
Received 0 Likes
on
0 Posts
Oei Airbus Operations
Ok just a quick question.Can someone please explain what, if any, the managed speed target will do differently if you experience an engine failure in the Alt Crz mode as opposed to the Alt mode?
Sure i can recite the Fcom 4 explanation but it still is as clear as mud to me
Sure i can recite the Fcom 4 explanation but it still is as clear as mud to me
Join Date: Jan 1999
Location: hongkong
Posts: 187
Likes: 0
Received 0 Likes
on
0 Posts
Flaps One
No I don't think so. If in ALT mode we could still be using managed speed.
Everyone I ask seems to think that the FMGS will give 'Green Dot' whenever there is an engine failure, but as FCOM 4 describes this is far from the case! The a/c might begin to drift back to GD even with the EO CRZ SPD showing on the PFD since there is unlikely to be enough thrust at altitude, but of course that was not the question!
If the a/c is in ALT mode (or actually in V/S zero as we would be the case when accelerating at EO ACCEL ALT) the FMGS will take into account any speed constraint ahead if still using managed NAV. In this way when very heavy, for instance, we might never get to GD (this dependant on if we are still in FLX/MCT not TOGA!).
No I don't think so. If in ALT mode we could still be using managed speed.
Everyone I ask seems to think that the FMGS will give 'Green Dot' whenever there is an engine failure, but as FCOM 4 describes this is far from the case! The a/c might begin to drift back to GD even with the EO CRZ SPD showing on the PFD since there is unlikely to be enough thrust at altitude, but of course that was not the question!
If the a/c is in ALT mode (or actually in V/S zero as we would be the case when accelerating at EO ACCEL ALT) the FMGS will take into account any speed constraint ahead if still using managed NAV. In this way when very heavy, for instance, we might never get to GD (this dependant on if we are still in FLX/MCT not TOGA!).
Join Date: Jan 1999
Location: hongkong
Posts: 187
Likes: 0
Received 0 Likes
on
0 Posts
Because the FMGS uses the same principles when engine out in ALT as it does when V/S zero. In early mod states of the FCU/FMGC after a delay V/S zero would revert automatically to show ALT on the FMA. Doesn't appear to do this now.
Join Date: May 2000
Location: Glorious West Sussex
Age: 76
Posts: 1,020
Likes: 0
Received 0 Likes
on
0 Posts
ALT CRZ implies CRZ phase, FlapsOne is correct, and in practice that means no change from current speed unless you are flying slower than EO CRZ SPD. Not Green Dot 'cos the other engine(s) would reduce thrust, which is normally undesirable at this point.
ALT implies CLB or DES phase: target speed is set to EO CRZ SPD at the FCU altitude (i.e. current speed is not an option). Always subject to limit speed.
Cheers, TP
ALT implies CLB or DES phase: target speed is set to EO CRZ SPD at the FCU altitude (i.e. current speed is not an option). Always subject to limit speed.
Cheers, TP
