Posts about: "Flaps (All)" [Posts: 165 Pages: 9]

The speculation that the pilot monitoring retracted the flaps instead of the gear is a valid one. There are a few incidents off the top of my head that I can think of. The BEA trident in Staines that stalled and crashed had had its droops retracted early, the Nepal ATR on approach, the PF called for flaps 30 and the PM pulled the props to feather and more recently when the BA 777 pilot at Gatwick pulled the power back instead of pulling on the yoke at Vr. As they say, if it can happen, it will happen.

I am curious how this can happen? The handle for the gear is on a completely different place in the cockpit that the flaps handle.
Possibly a B787 pilot could give us an idea?

What is nearby the flaps handle are the switches for the "fuel control".

LE devices extended on impact would correspond with the B787 auto-gap function that extends the slats in certain low-speed high AOA conditions for stall protection (aka "Autoslats"). Which this aircraft most certainly was in before impact.

Only to say, that LE devices seen extended on the crash a/c don't prove configuration on takeoff.

B777/787 rated/current/active pilot.

B787 FCOM:

BOEING, AIRBUS, MD, it doesn't matter, handles for Gear, Flaps different places, different shape. But it has happened and it will happen.....

that\x92s why the switches and levers are designed like this. The gear lever is round like a wheel and the flap lever is, well flap shaped. Mixing up switches was/is common. Happened to me in my training pulled the mixture full out instead of carb heat on my approach. Immediately realised the change in the engine and pushed it back in before it cut out completely and engine started up again. Change of underwear required.

Ive seen it happen in a previous (ground based) life fairly frequently (in relative terms) but exclusively during descent/approach. Usually the context would be expecting a flap call but when the gear call is made the flap handle is moved and quickly returned to the previous gated position followed immediately by gear selection, confirmed upon review of the data. To happen on takeoff would be most unusual, and although the CCTV footage is indicative of it being highly plausible, neither pieces of footage really show anything to draw any conclusions on. Certainly there may be numerous aspects to this, perhaps there was some catastrophic electrical failure that wasn\x92t of itself an immediate threat to the flight but the startle effect in the flight deck prompted other reactions. It\x92s impossible to know based off the information available. The human element will form a significant part of the investigation regardless of root cause(s).

Regarding the comments about who should be allowed to comment on such threads. I like the fact the mods have taken a pragmatic view of this. Theres a reason many in the accident investigation field come from an engineering background. Whilst highly experienced pilots are clearly crucial on an SME level, there can be a tendency for iwouldnthavedoneitthatway-itis. This can at times hinder investigations where an open mind free from confirmation bias is essential.

No, it really isn't. For one thing if they retracted flaps, their speed would have increased, however distance and time tells us that their speed substantially decreased from takeoff to impact. Hardly possible with less flaps, descending, and take off thrust.

Compare the video with a normal plane flyover. The lack of engine noise, and propellor like sound of the RAT is so blindingly obvious I don't know how people are still going over the flaps thing.

Just a few examples:

https://assets.publishing.service.go...MAJS_01-12.pdf

https://www.aeroinside.com/11716/eas...stead-gear-up#

Also I remember a similar story in "Fate is the Hunter"...

And another: https://www.gov.uk/aaib-reports/aaib...319-111-g-ezew

In an Airbus the flap lever is even further away from the gear lever than in any Boeing, yet still it happened! Action slips are just that and to blindy say that moving the flaps before gear is impossible, just because they are in a different location is incredibly naive. Next time you pour orange juice in your tea because you were thinking about something else and grabbed the wrong carton will you decry it impossible?

To be as crystal clear: I am not saying this is how it happened, but it could be. Just as other things could be.

SLF here, retired physicist, but with much engineering (esp. systems engineering) background and considerable interest/experience in fault-finding in complex (not aircraft) systems.

I think it is helpful here to work through some possible failure scenarios in some detail. You could usefully partition these into two separate groups: “RAT was deployed” and “RAT was not deployed.” I’ll mostly follow the former here.

\xb7 By following this path, I think we can exclude incorrect flaps setting or premature flap retraction as the primary cause of the crash. It’s difficult to see how improper use of the flaps would be correlated with RAT deployment. Everything in this case points to a loss of engine thrust.

\xb7 The first question is, why did the RAT deploy? As I understand it, manual deployment by a pilot is possible, or automatic deployment caused by detection of major electrical or engine failures. I haven’t found an authoritative, detailed discussion of this, or about the time to deployment, which is relevant here as there is so little time involved.

\xb7 According to tdracer , if the primary issue was a major electrical failure, that should not have caused any engine rollback. Thus, absent pull back of the throttles (which surely would have been corrected by the pilots), there should not have been a loss of thrust.

\xb7 Thus we are left with engine rollback as the likely underlying problem. Absent other issues, a single engine rollback should not have been a major problem, so dual rollback, unlikely as it might be, seems a reasonable conclusion.

\xb7 This is consistent with the reported mayday call, although that report needs confirmation.

\xb7 It is difficult to understand a dual engine rollback. Various causes have been suggested but ruled “unlikely” here. However, it is not possible to rule out a unicorn event, like the dual engine rollback experienced by BA 38. Leaving aside the cause, it is useful to look at the consequences.

\xb7 There would have been a major loss of electrical power (apart from battery backup), assuming the APU was not running. I don’t know if is possible the APU might be used at takeoff (e,g., to unload the main engines), or if any evidence from the tail photo at the crash site provides a meaningful indication (e.g., intake door status).

\xb7 Are there other indications of loss of electrical power? The reported statements of the surviving passenger may have some relevance, but I would want to see the results of an interview by crash investigators.

\xb7 What about the loss of Flight Aware ADS-B data shortly after takeoff? There have been a few mentions of this, but not much discussion. Could this indicate loss of electrical power?



I hope this is of some use. I’m happy to defer to professionals or others here for better information/analysis.

I still don\x92t understand the flap retraction theory

It happens- in every airline in the world, ask any of their training/FDM departments. There are reported incidents of it from almost
Every major airline I can think of. Humans are incredibly fallible, I\x92ve spoken to a captain who did this on the 737 back in the day (now flies Airbus) and on that day he caught himself. He said in the debrief after the flight he could not explain why he did it, absolutely no clue.

The issue I have is why one of the most modern aircraft in the world, a thoroughly 21st century clean sheet design with every protection under the sun would not have the adequate protections or performance to deal with this scenario. Surely the 787 has high AOA and low speed protections- those engines should\x92ve been screaming at TOGA LK (or the Boeing equivalent) and the pitch should have been limited regardless of the weight, density altitude etc

Airlines and manufacturers will always try and blame the pilots but I would be truly shocked to learn a FBW aircraft (Boeing or not) designed this century could get itself into such a catastrophic state so innocently. We KNOW many crashes have been prevented by Airbus FBW protections (a few Wizz examples come to mind

We're all shouting each other down with two main different theories on why the aircraft lost lift so shortly after takeoff.

1) Incorrect flap retraction causing the aircraft to lose lift and unable to recover the energy in time. (Not unheard of and plenty of reports where this has happened - albeit usually not to a crash).

2) Loss of engine thrust backed up two potential pieces of evidence that back up the RAT was deployed (apparent RAT sound, potential RAT seen on low res video).

It is impossible to know which of these is the case. Considering this summary of memory items is there the potential for a combination of both theories to have taken place?

Inadvertant flap retraction by PNF leading the PF to sense a sink and loss of lift. Pushes the thrust levers forward to the firewall and still the aircraft sinks. PF looking through the HUD and so very much 'outside focused' and doesn't realise that PNF has instead moved the flaps. PF defaults to memory items for loss of thrust on both engines before PNF can realise or communicate to PF what they've done, start switches are cut off which drops the RAT and from that point they're only heading one way. This would satisfy the strongly held belief that the RAT was extended, whilst also following the more likely initial cause of an action slip by PNF starting the sequence, rather than a dual engine failure.

Neurotypically an error in an automatic action will occur when the routine that encompasses that action is changed. Hence babies being left in back seats of cars, and probably a factor for the sterile flight deck rule. Any reason to think that might have been in play here?

It's tempting to think that, however one may also have made the case 'why doesn't Boeing install a system that prevents the nose getting too high on the 737 MAX? Then they won't have to retrain crews on handling differences'. We know how that worked out.

When designing anything you need to account for unintended consequences and the possibilities for that system adversely affecting safety if it were to malfunction. If you introduced a system designed to prevent flap retraction 20 to 30s after liftoff, what if failure in a channel of that system then prevents flap retraction required to achieve a MACG with critical terrain on departure. We could 'why don't they do this / why don't they do that' until eventually we end up with not flying at all.

On your point of integrated scales, there is a far easier way to cross check actual aicraft weight with calculated weight: a computer that cross references acceleration data on the takeoff run with known values from lookup tables based on specific environmental conditions and engine thrust settings. If you're not accelerating at a normal rate expected for the calculated thrust and weight a warning can be triggered. This was a recommendation echoed by the AAIB following the incident with a Jet2 aircraft getting airborne at only 70% thrust. I believe Airbus and Boeing are looking into the potential implementation of such a safety system.

Exactly like the action of lifting the flap lever out of detent before moving it. What is significantly different is that you would have to do it twice. It is that which makes it improbable unless intentional.

This I believe is an option to retrofit. Can\x92t recall the supplier, Honeywell perhaps, not sure on the 737-MAX and whether it has anything fitted as standard.. Anyway the more cost effective option (for NG operators) is to amend SOPs where appropriate. However the U.K. CAA do apparently intend on creating a working group regarding such events. See also the TUI event at BRS.

https://asn.flightsafety.org/wikibase/388602

https://simpleflying.com/aaib-report...f-runway-10ft/

It\x92s worth noting that the acceleration rate was exceptionally low in the TUI event based on the average for that airport. I refer you to my initial post on this thread, it\x92s a risk that there is no config warning horn (to my knowledge) on the B737-800 that will alert the crew, upon selection of TOGA, that the performance solution entered into the FMC does not agree with the actual config. In the case of flap setting, it will only alert if a non standard take-off flap setting is selected. If in the unlikely event TOGA is not pressed at all then\x85..

Airbus have added something of an FWC to their 321NEO aircraft that will alert crew to this - something I\x92d heard from bus mates but wasn\x92t 100% certain on so thanks to those on here that confirmed.

Sorry for further thread derailment, however felt it might be of interest. 787 rated crew on this thread suggest this would form part of the electronic checklist on the aircraft so in the case of the event at hand a red herring.

Why the need to make the two theories fit in such a convoluted manner? Inadvertent flap retraction was theorised because people assumed that was most likely to have caused the loss of lift - hardly anyone believed dual engine failure was possible. Now we know that the loss of lift was indeed almost certainly caused by a loss of engine power, why all these awkward attempts to reverse engineer it to still fit the flap retraction theory? People need to realise they are only trying to make the flap retraction theory fit because of cognitive biases. If we had all been told immediately, there was dual power loss and the RAT deployed, no-one would even be considering flaps. Its confirmation bias of past assumptions, that's all.

As has been said many times as well, the landing gear retraction process appears to start as the bogies tilt, and then suddenly stops. Which rather suggests they did pull the gear lever. Based on the videos and the amount of speed the plane lost in the very brief sequence ovents, I'd say that the plane lost power a lot earlier than it would have in your theory.

How do we \x91know\x92 that, exactly?

Good summary, I'd just say the thrust levers definitely weren't firewalled. The plane lost a huge amount of speed by impact. This single fact should be enough to end the flap retraction theory. It lost a huge amount of speed while descending - now what might cause that? The gear also begin the retraction process (bogies tilting). The obsession with flaps when there isn't a single piece of evidence for it is very odd. (not suggesting you are guilty of it btw).

The requirement to lift the cutoff switch out of the detent before moving it is an important point. However, those switches are close together and unless the the detent requires significant force I suggest that they could be operated together with one hand if that was an intentional action.