A320 - Speed after Acc Alt
Thread Starter
Joined: Nov 2006
Posts: 367
Likes: 0
From: Tropics
A320 - Speed after Acc Alt
Hi everyone,
On two separate occasions, I have experienced a situation whereby the speed is automatically selected after Acc Alt, where the FMGS mode changes from SRS to CLB mode. Both departures we had our standard 800/800 in the FMGS for Thr Red and Acc Alt; and as soon as the FMGS changes to CLB mode, the speed was automatically selected in the speed window at 172 and 167 on the 2 respective departures. I can't recall however, if these speeds were the exact target speeds during SRS.
I should add as well, that we had pre-selected green dot speed for both departures on the CLB page during the FMGS preparation; and we expected to see that pre-selected speed as target speed as we go into CLB but it 172 and 167 came up on those 2 departures.
I can't find any explanation for this, but I'm still very new on this machine so pardon me and I appreciate any ideas!
On two separate occasions, I have experienced a situation whereby the speed is automatically selected after Acc Alt, where the FMGS mode changes from SRS to CLB mode. Both departures we had our standard 800/800 in the FMGS for Thr Red and Acc Alt; and as soon as the FMGS changes to CLB mode, the speed was automatically selected in the speed window at 172 and 167 on the 2 respective departures. I can't recall however, if these speeds were the exact target speeds during SRS.
I should add as well, that we had pre-selected green dot speed for both departures on the CLB page during the FMGS preparation; and we expected to see that pre-selected speed as target speed as we go into CLB but it 172 and 167 came up on those 2 departures.
I can't find any explanation for this, but I'm still very new on this machine so pardon me and I appreciate any ideas!
Ut Sementem Feeceris
Joined: Jul 1999
Aviation Qualifications: ATPL
Posts: 4,793
Likes: 2,317
From: UK
Was there a speed constraint in the FMGC flight plan? i.e. you've got a turn which requires speed to be held back (but 167/172 knots seems very slow) this is sometimes coded as a constraint. However, this should not result in the selected speed appearing in the FCU - that only occurs with a pre-selected speed on the CLB PERF page, and then you "manage" the speed once you don't need it any more. With an FMGC FLT PLN waypoint speed constraint, this will jump to CLB speed once the waypoint is sequenced.
Is this A318/19/20 or 321. If the heavier types those speeds are looking like V2+10 depending on TOW. Odd.
Hopefully you didn't clean up......
A4
Is this A318/19/20 or 321. If the heavier types those speeds are looking like V2+10 depending on TOW. Odd.
Hopefully you didn't clean up......
A4
Thread Starter
Joined: Nov 2006
Posts: 367
Likes: 0
From: Tropics
Both of us we watching the speed tape for a moment and wondered why it didn't command a target speed of what we have preselected in the FMGC CLB Perf page at acceleration altitude. Certainly it wasn't in the SID, the departure was familiar to us so it was even more strange. Certainly we didn't clean up, but now coming to think of it it was the same aircraft on the two separate flights.
Could it have been just a bug somewhere? And, it's an A320.
Edited for SP
Could it have been just a bug somewhere? And, it's an A320.
Edited for SP
Last edited by dream747; 26th November 2012 at 10:17.
