PPRuNe Forums - View Single Post - Air France B777 control issues landing CDG
Old 9th Apr 2022, 06:45
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Originally Posted by suninmyeyes
Just a suggestion as I have seen a similar thing happen on a 777. One pilot is manually flying and the aircraft is on an intercept heading for the localiser. He asks the other pilot to arm the localiser. The P2 accidentally pushes the button next to it which is the autopilot engage button. The buttons are identical, small and square. The autopilot then engages and will maintain the same heading and descent rate and they will go through the localiser.

The pilot flying then thinks the controls have frozen. It is a busy time for the crew and there is a high workload. The warning you hear is the config warning which is probably because land flap was selected just before the gear had locked down. You then hear the autopilot disconnect warning which is at the point where things probably started to return to normal where the crew realised what had happened. I am not saying this is exactly what happened but from my experience and the noises it would be a plausible scenario.

I too think it is unlikely that there was a major control problem with the 777 and that is was more likely to be finger trouble. However we are all human and it would be wrong to specifically blame Air France. The autopilot engage buttons for both Captain and copilot, the autothrottle engage button and the localiser and approach buttons are all the same small square button. Yes on takeoff at Lagos the Air France crew accidentally pushed the autopilot engage button instead of the autothrottle button and thought the controls had jammed and rejected the takeoff bursting tires. They are not the only airline to have done that and Boeing have changed the logic to stop that particular error being made again.

I’ve always thought that this was an exceptionally poor piece of ergonomic design on the part of Boeing - the A/T switch, A/P switches and APP switch are identical and very close together - it has led to incidents in the past. When a conscious effort is made to differentiate other controls and switches (flaps, gear, strobes, landing lights etc.) what was Boeing thinking here?

In this incident looking at the graphs posted earlier, it appears that the LOC deviation occurred at exactly the same time that the vertical speed started increasing. I’m thinking that possibly the waypoints hadn’t sequenced, they went around due to unstable approach (gear not down? - master warning is definitely gear configuration warning) , and the aircraft attempted to turn back to the previous waypoint, hence the deviation. The deviation commences very close to 1000’ baro altitude - not sure what AF’s stabilised approach altitude is but 1000’ is typical, so this would fit in with that theory.

The only bulletins from Boeing re. 5G relate to interference with radio altimeters - there is no mention of the possibility of LOC interference, it’s most likely a different band altogether. LOC operates in the VHF band, 5G as far as I am aware operates predominately in the UHF band.
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