Posts about: "Action slip" [Posts: 61 Pages: 4]

It looks like an action slip to me as the timing looks right ie \x93positive rate \x93 \x93gear up\x94 (someone raises the flaps instead of the gear) PF is looking through the HUD so just sees someone move their hand rather than the hand moving the correct lever

It\x92s then taking off heavy weight with 35c and the flaps have been raised and the gear is still down.

As nobody realised the flaps had been raised instead of the gear when it happened they automatically think it\x92s some other issue as the aircraft loses lift and the amber band rapidly rises and the aircraft runs out of lift.

could be something else like fuel or 2 engine failure but seems possible it\x92s an action slip also.

I didn\x92t see the RAT deployed but saw the gear down still and an aircraft fall out of the sky with what sounded like engines running still.

In the high-def photo of the wing post-crash that has been posted in this thread, the flaps are visibly extended.

Also, unless we are all watching very different videos, I don't quite understand how anyone cannot hear the propeller buzzing in the video of the plane passing overhead. It's quite distinct. Though of course in this new age of AI we should take any and all audio/video with a grain of salt - which is exactly why confidence that the flaps are or aren't retracted based on such low-quality footage is a bit silly to me.

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.

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.

A summary of the more certain things we know about the accident so far:

The takeoff run was from the full length and appeared normal, even after comparing with the same flight on previous days. This very much reduces the likelihood of it being a performance issue, e.g. wrong flaps, derate, ZFW/TOW, etc.

Shortly after takeoff, the gear started retracting but stopped in an early intermediate position. At the same time the aircraft climb rate dropped off, then it started a shallow descent. This is consistent with a loss of electrical power causing a loss of hydraulic pressure and total engine thrust from both engines reducing below that generated by one engine at the takeoff setting. The position reporting also went offline at that moment, indicating that it was likely load shed due to an electrical malfunction. What exactly caused the engine/electrical issues remains speculative. An action slip mistaking flaps for gear seems much less likely as due to the above, the correct selection was probably made.

From the videos of the last moments, there is strong evidence that the RAT was deployed, which has a very short list of possible triggers. The sole eye witness from inside describes power issues which lends credence.

Taken together, it seems that there was an event (or events) shortly after rotation that compromised both engines and the electrical system. There is no evidence yet of birdstrikes and continued engine operation *should* not be affected by the aircraft electrical system as they are independently/internally powered, so logic would have the engines failing first leading to a cascade of other problems. Something that affects all engines pretty much simultaneously is a rare beast but it has happened in the past; outside of a deliberate selection of the fuel and/or fire switches for both power plants there is fuel contamination, FOD and not much else. Its seems at least one FDR has been recovered so depending on where they take it for read-out, we should get some initial facts fairly shortly.

This indeed is the best summary till now

This to me makes more sense; perhaps I`ve got it wrong but in the video the trailing edge flaps definitely look up. Maybe there`s more and they weren`t.

On a flap 5 takeoff the FMS could be programmed to select climb power at flaps 1 which would seem like an apparent loss of thrust. Same as for F15 to F5 or further.

I`m not sure if they would have cycled the FCS switches or not. But the airplane certainly would have experienced a loss of lift would the flaps been inadvertently retracted. As well as perceived loss of thrust.

OTOH any castastophic failure which left the gear down would have essentially left the flaps where they were. They are hydraulically activated with electrical backup but it`s wayyyyy slow.

Well, it\x92s narrowed it down to 3 possibilities:

Action slip
SAIB NM-18-33
Intentional.

I would add a fourth, however unlikely it might be: some kind of electrical short which caused the "cutoff" signals to be sent without the physical switch moving.

The SIAB relates to defective throttle units at the point of installation (on a different but related aircraft). I might be onboard with that theory if maintenance happened to have replaced the unit a day or 2 before the incident. But it's a tough sell that a defective switch that's used literally on every flight had flown for 2 years without someone noticing and snagging that the locking mechanism wasn't working

I'd like to say something here that might help us all understand what probably happened. It's sad, but now that we know some clear facts, I think this probably goes a long way to understanding this tragedy.

It's a bit long, but that's probably necessary. I hope you find it worth the read.

First up, I notice there's a tradition here to talk about "muscle memory". I understand it, but this is really quite the wrong term, and I think using the correct term will help clarify this a great deal. The muscles don't remember actions (at all, I think). It's part of the brain that's responsible (and I truly think that aircraft designers need to understand and take this fully into account when designing new aeroplanes/airplanes.)

The part of the brain in question is called the Cerebellum. It has been called "The Brains Brain" but again, that's inaccurate. The cerebellum is actually the brain's Automaton! Pretty close to automation, and in some ways, nearly the same.

The Cerebellum is located at the back, lower part of the brain. It looks quite different, and appears to have a stringy appearance. This part of the brain is responsible for all manner of physical (i.e. motor) actions. It is like an ECU or an EEC or a FADEC, or a GPU or all manner of sub-processing units in cars, planes, factories and so on, and I guess, in virtually all animals and humans. Basically, it is designed to take a lot of the workload off the brain itself. That's where the problem arises.

Just think about walking. You can work along without even thinking about it. In fact, if you do think about it, your walking is likely to become "unnatural". Just think about how it feels to nervously walk on stage in front of a big crowd. Am I even walking properly...? I feel like a robot! The conscious mind has taken control, and it's not as good at walking naturally as the cerebellum is. After all, it's been the one doing it, all your life.

So, think about talking, writing, signing your signature, typing, riding a bike, stirring your tea, driving a gold ball, playing a well-practised video game. Think of "Getting the hang of it" - it's the process of the cerebellum learning a new sub-routine. Slow to start, but capable of lightning fast action once learned. And some of its learning is evidently built-in from birth. Eye movement (& focussing?), for example.

So, having a cerebellum allows you to walk very successfully, while watching the traffic, talking to your companion, thinking up jokes, listening to the birds singing, etc etc. You don't need to think about it, because your cerebellum has learned since you were a toddler "How to Walk". It knows very well, and can even handle trips and especially slips. All you have to do is say "Walk to A" and the cerebellum does it, unless the thinking brain says "Hold on, stop."

This is where the term "muscle memory" comes from. Automated actions, not from muscles but from the cerebellum.

Now, the problem here is that in effect, what I'm describing is, in a way, two brains. Scary thought! Even more scary when you recognise that it's virtually true.

If you take a look at the anatomy of the brain in a suitable drawing, you'll see that the cerebellum is not fully connected to and integrated with the rest of the brain. It's actually a separate sub-unit which is not even wired directly into the brain (the cerebrum, just to be confusing) itself. It's attached / wired to the rear side of the brain stem, below the Main Brain:

https://teachmeanatomy.info/neuroana...es/cerebellum/ - scroll down to Fig 1.

Those of us who understand computers, networks, data-buses and so on will immediately recognise the problem. For a start, there's a bottleneck. And a source of latency. (The perfect word for this situation.) There's also a need for multiplexing - or, you could say switching. At least, there are two possible sources of control. Just like in the cockpit! Oh No!

Having the cerebellum where it is had/has a huge survival advantage. It means it's much "closer" to all the nerves that control the muscles - so that in life-threatening emergencies, the cerebellum can get the commands out much, much faster than the conscious brain can even think of them. If you're falling, the cerebellum will have reacted even before you've had a chance to think.

I learned this one day in England. I was riding an old bike to work, accelerating at a roundabout as hard as I could push. Suddenly, at full push, the chain came off. I don't (and didn't) even remember, maybe didn't even see, what happened next. One moment, I was up on the pedal, pushing hard. Next, I was in mid-air. Seriously, I remember this. I was in mid-air on the right-hand side of the bike, looking back towards the bike still rolling along beside me as I was falling. I was already about half turned, nearly onto my back. No idea how. (I was wearing a backpack, so apparently, it was my designated crashpad.) Next, I was on the road, completely free of any entanglement with the bike. It (cerebellum) didn't manage to get my right elbow out from under (maybe deliberately) but I landed mostly on my backpack, with my elbow pinned about under my right hip. The scars have faded now, but my forearm/elbow became a brake pad... Next thing I remember was sliding along a cold but fairly smooth section of road, head craned up, looking back down the road to see if anyone was going to run me over. A brown-haired young woman in a car was coming behind me, safely, watching, slowing. I firmly believe that my cerebellum was responsible for me landing so well. Nothing broken, just some skin off my elbow. Like I say, I didn't have a chance to even think about it.

So, there's a big advantage in having a semi-autonomous processor operating in parallel, alongside the higher intellect. But every advantage seems to bring with it a downside, as I think we might all be seeing.

The downside is, given a command by the cerebrum, the cerebellum will perform it. Accidentally, unintentionally, mistakenly, prematurely, casually, give it the wrong command, and guess what?

To tell you the truth, the older I get, the more often this happens. My wife and I jokingly call it Autopilot. We're out shopping or whatever, a list of places to go, me at the wheel. A to B to C... Suddenly, we're back home, and I forgot to stop at the Drug Dealers... I jest - I mean, who would forget that! But talking is a great way to facilitate this. The cerebellum knows the way home far better than the way to the Candlestick maker, so, when lacking clear direction, evidently, it reverts to the most familiar.

Exactly what happened here, who can really say? Not me. But this article (many thanks to https://www.pprune.org/members/198630-limahotel ) for this link.

It's totally relevant, the PF the obvious cause:

https://avherald.com/h?article=48d1e3ae&opt=0

I wonder what might have been the trigger here. Sudden high stress? Why didn't the gear go up? Who should have done that? When, compared with actual events? (Might have already been answered, sorry. I've been busy! )

I don’t know if the FDR measures the switch position or the electrical signal. The latter is probably more likely, although there has been much discussion around potential scenarios involving accidental switch movement as well as possible causes of electrical glitches. Let’s assume that the switches were actually moved, and ignoring the “bad faith” scenario, we need a situation that encompasses the switches being moved to Cutoff by one pilot, this action being queried by the other pilot and denied by the pilot who moved the switches.

For consideration, here is a possible scenario that hasn’t been mentioned yet and encompasses the frailty of human performance. The report mentions that the flight crew on the immediately prior flight had written up a "STAB POS XDCR" status message, and that troubleshooting was carried out. I wonder if the scenario could be that the accident crew received a Stabiliser EICAS message on or around take-off and the Capt (who was PM) decided to action the first checklist item immediately from memory, by intending to move the Stab switches to Cutoff but moving the fuel switches instead. As in all modern Boeings, the Stabiliser Cutoff switches are immediately next to the Fuel Cutoff switches and operate in the same sense (i.e. down for Cutoff). They are guarded and never normally moved but, with an intent to move the stab switches, “muscle memory” (cerebellum activation if you prefer) may have taken the Captain’s hand to the Fuel switches, which are operated on every flight. The FO (who is PF) is manually flying at this stage sees and queries it. The Capt denies it, as he doesn’t realise what he has done (confirmation bias perhaps). After a few seconds, the terrible mistake is realised, and the fuel switches are moved back to run, but sadly too late and the Capt makes a Mayday call.

Perhaps a bit of a stretch but not as much of a stretch as many of the other scenarios in this thread. I think it is a real possibility. Sadly, the only other explanation that I can see is the deliberate “bad faith” scenario, which we would all hope is incorrect.

Fly Safe
PJ88

A plausible theory, however, if that were indeed the case wouldn't supporting FDR data be available/have been included in the initial report?

This crossed my mind too. This is called an "action-slip" by designers: a valid and frequently practised action being applied to entirely the wrong situation, resulting in an (extremely) invalid action.

On this flight, the relative drop in noise and calm that follows the landing gear doors closing after the gear retracts during the initial climb, might have caused an action slip by PIC to perform the engine shut-down procedure used when parking on stand.

Unlikely though, I would hope.

Just read all 16 pages - been flying! I think comment \x93why did you cutoff\x94 is not the reaction I would expect from a Training Captain who has just witnessed the co-pilot turn both fuel control switches off. They would possibly utter an exclamation, but would surely correct the error immediately - this didn\x92t happen for 10secs. The words are more likely to have come from an FO who has both hands on the control column and is concentrating on the rotation.

Every flight we do as PM we move both fuel control switches to cutoff, 1 after the other, with a gap of about 1 sec between each one. It\x92s a learnt action in response to the phrase \x93shutdown\x94.
Every sim the TC has conducted he will have moved critical switches without much thought in order to setup the sim for the exercise. I remember being slightly shocked one day on the aircraft, having been training in the sim the previous day, that I nearly operated a critical control without thought. It\x92s something I had to consciously guard against after that.

There is no rational explanation for doing it though - moving both fuel control switches down instead of moving the gear lever up is not a likely action slip. It seems either a totally subconscious act or a totally deliberate act.

The gear were never retracted on this flight, so the action being caused by gear up quietness is not feasible.

Action slip in general... technically possible, but there should still be no actions being taken other than gear up (and probably still a bit early for that).

Engines off instead of gear up is one hell of an action slip.

Seriously??
Come on! The gear never moved! You're an Airbus pilot; do you really think that could happen? If so, would the captain then sit there fat, dumb and happy wondering what was now going on... for 10 seconds? Even I would say "Sh1t" and whip those fuel switches back on quicker than the FO could say "WTF!".

Mods, if you don't lock the thread, I'm going back to Facebook!

I don't think this answers my question? Evidently there is an interruption in power, the (quite stable, at that point) ADS-B stream cuts out and doesn't return for the final twenty seconds of flight. And there are other indications that non-essential loads were shed, like the survivor remembering what must have been emergency exit lighting in the cabin. Though I would have liked explicit confirmation of AC power loss happening or not in the report.

The timing of data loss seemingly lining up with the first cutoff switch being flipped back to RUN seems a little too coincidental to me, but again hopefully someone with relevant knowledge has a mundane explanation for this.

Regardless of what actually happened in that cockpit, reasoning like this seems completely backwards to me. Since when do humans reliably, instantly recognise that they've just made a mistake? If they were that attuned to their actions they're almost certainly attuned enough to not make the mistake in the first place, especially if we're talking about an action slip. I've e.g. absentmindedly added salt to my tea instead of sugar and I certainly didn't immediately realise that I'd done that - in fact it took a good few seconds even after sipping and spitting it out for my brain to catch up to what must have happened. Even if an observer had pointed out to me before drinking it that my tea had salt in it, I would just have been confused because obviously I wouldn't do something that silly (spoiler alert: I did).

On top of that I feel like people are overestimating how long ten seconds actually is, especially considering some of those seconds are reported to have been taken up by confused dialogue (that isn't even reported in its entirety). I thought it was common wisdom that accidents are never down to one thing; it would be light-years from being the first time that suboptimal crew response turned a maybe-recoverable error into a definite disaster without an ounce of malice in the mix.

Ah, OK, noted re the gear. But there must have been some other distraction that led to an action-slip. For example, why wasn't the gear retracted ? - it is a very clear sequence: " V1......Rotate......positive climb......gear up....." So something else must have happened to distract both pilots.

Perhaps the brakes were hot, so maybe they deliberately delayed bringing the gear up to let them cool first - (an occasionally needed but standard procedure). This uncommon sequence in turn might possibly have led to an action slip.

But action-slips are exactly that. A valid action applied to completely the wrong situation. E.g putting the milk in the bin or the microwave instead of back in the fridge.

Highly unlikely, I know, but..............

Not only that but if it was an action slip it wouldn\x92t have been BOTH cutoffs one second apart. Clutching at straws indeed.