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Wizz A320 at Sofia on Jan 3rd 2016, inadvertently retracted flaps on final approach

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Wizz A320 at Sofia on Jan 3rd 2016, inadvertently retracted flaps on final approach

Old 23rd Mar 2021, 17:43
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Wizz A320 at Sofia on Jan 3rd 2016, inadvertently retracted flaps on final approach

https://avherald.com/h?article=49de3dbc&opt=0
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Old 23rd Mar 2021, 17:48
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Are we referencing at a 5-year-old incident for any particular reason ?
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Old 23rd Mar 2021, 18:00
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Hope nobody starts a discussion on the technical aspects of the SRS activation logic as it could have happened on any aircraft with the same results.
The question more than anything is what on earth has brought the PM to retract 2 (two!) steps of flaps on approach.
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Old 23rd Mar 2021, 18:50
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It sounds like someone messed up in a big way, managed dig themselves out of the hole and nobody was hurt
Unlikely to be either the first or last time a pilot (not just at Wizz) has made a significant mistake and then recovered from it though
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Old 23rd Mar 2021, 19:19
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True, but selecting Flaps 0 at 4NM on final when called for Flaps 3/Full means that this chap should really be somewhere else rather than in a flight deck.
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Old 23rd Mar 2021, 20:06
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Not the first airline for this to happen to and I doubt the last. I don’t know why so many seem to get it wrong perhaps it is because they have a memory of rapidly cycling the lever in training as the sim is reset for the next exercise.

Last edited by tubby linton; 23rd Mar 2021 at 20:19.
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Old 23rd Mar 2021, 20:54
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sonicbum

Perhaps fatigue was a factor?
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Old 23rd Mar 2021, 21:00
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Things can get confusing very quickly.

Would it make sense for Airbus pilots to have thought in advance that if things start going the way they did here(or something similar), then don't just disconnect the autopilot, but also take the thrust levers out of any detents and manually fly. Otherwise, you might get these situations of thinking you are at CLB thrust when it is really at idle.

It sounds like the PF on this flight got the "get rid of the automation" in terms of autopilot part of the automatics correct but not the autothrust part of the automatics.
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Old 23rd Mar 2021, 21:07
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This seemed like quite a rollercoaster ride that could have been avoided by better monitoring (monitor the config change, monitor the FMA etc). I am absolutely no skygod, heck, I'm definitely worse at manually flying a plane now then 6 years ago when I flew a plane without autopilot. But previous experiences on that old plane have instilled a fairly strong habit of monitoring and cross checking in my flying, and it helped prevent a similar incident maybe a month or two ago. I asked for next step of flap extension, FO raised flaps by one step instead. Caught it within a second or two luckily, reselected the desired flaps, mentally cursed at the FO for a split second, continued the approach as all was still in good shape and stable.

After shutdown at the gate I asked the FO what happened but no clear explanation or reason for the flap retraction was available. Normally a decent pilot, just seemed like a massive brain fart. Anyone recall the Luxair Dash-8 gear retraction on rotation? One of the conclusions there:

The early, not requested, grasp of the landing gear selector lever during the take-off callout procedure came suddenly and unexpectedly for the PF. After the event, the co-pilot could not explain her actions.

Publications on human performance and error management (see page 16 ff) describe such actions as Slip. It is a spurious action which occurs unintentional und unplanned in a correct, known, often trained and repeated course of action. Especially processes which are repeated quite often and therefore generate reduced concentration are susceptible for these kinds of errors.
And of course, an often recurring theme, some of the issues in this Wizz incident could have been prevented by reverting back to basics. The detents are there to help but you still have enough thrust lever travel assigned to manual thrust... Use it, AP off, AT off. Reselect once stable.
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Old 23rd Mar 2021, 23:39
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Originally Posted by sonicbum View Post
Hope nobody starts a discussion on the technical aspects of the SRS activation logic as it could have happened on any aircraft with the same results.
Actually, it wouldn't. While using thrust lever angle as TO/GA AFDS trigger is a very good design and very intuitive, it certainly proved to be less than optimal in this case, as only the thrust increased, but there was no change to AFDS mode - contrary to what a reasonable crew might expect on approach, should they select TOGA while established on the ILS approach.

B737 for example (and I would imagine other Boeing types would be fairly similar), uses separate TO/GA switches and they are armed as G/S is captured or flaps are extended or RA below 2000ft. If TO/GA is pressed outside of those conditions, nothing happens. So in this case, even if the flaps were selected to up, TO/GA would still engage as expected, as the G/S was captured and the aircraft was below 2000ft RA.
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Old 24th Mar 2021, 01:12
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The Airbus flap handle doesn't have the same protective gates that the Boeing aircraft have.
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Old 24th Mar 2021, 05:53
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Interested to find out why this was moved to the non-airline section.
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Old 24th Mar 2021, 05:59
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A few weeks ago we just discussed for flap selection if the call speed checked is necessary. Why can't it be silently done. Also ordering things in a bunch, like gear is still red but ask for next flap. It was by a Boeing pilot but Airbus guys also replied.This is one example if SOPs are not followed what happens. First ordering flaps 3 and full together. Then the PM selecting something but without checking the number going to the next selection again not checking the number. Had he looked for the number on SFI as is the procedure the mistake would have been discovered at the first wrong selection itself and the second flap selection would not have been made. It's almost as if it's a rule that for an incident to happen one mistake is not enough but a second mistake call it a confirmatory error has to be made.
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Old 24th Mar 2021, 08:13
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Originally Posted by Check Airman View Post
Interested to find out why this was moved to the non-airline section.
I would guess that the mods decided it's neither a rumour nor news and so doesn't belong in R&N, though IIRC there was a post about it soon after it happened.
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Old 24th Mar 2021, 10:28
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This reminds of the time many years ago when I was practicing a short field landing at Ipswich airfield, in a little Cessna 150. The flap control on those aircraft was a spring loaded paddle type switch. It had to be held down against the spring to select flaps down and when the required amount of flap was reached, letting go of the switch was supposed to bring it back to the central off position, into a detent. Moving the paddle up from that detent position caused the flaps to fully retract.

As I came over the hedge I selected full flap by feel and released the paddle switch. A few seconds later, to my horror, the aircraft simply fell out of the air and landed hard, quite a bit short of where I intended.

As I recovered my composure and prepared to taxi back in I realised that the flaps were already fully retracted, hence the aircraft no longer staying airborne.

The switch detent was worn so that releasing it allowed it to flick straight through off to the retract position.
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