Why are people still considering a flap/gear mix-up? If that were the case, I\x92d expect that with both engines running, one should be able to compensate for the loss of lift by increasing angle of attack and thrust - the latter might not even needed with TO thrust.

At this point, a dual engine failure seems like a much more plausible explanation. As for what might have caused it, I honestly don\x92t know.

There's two things which are unlikely to be related to this accident, but thought I'd mention them because they both concern software bugs that impacted 1.) The Electrical System and 2.) The Engines (both of them at the same time!)

US aviation authority: Boeing 787 bug could cause 'loss of control'

https://www.theguardian.com/business...oss-of-control

ANA Boeing 787 Dreamliner Suffers Dual Engine Failure On Landing:

https://simpleflying.com/ana-dual-en...re-on-landing/

Not yet seen a response to my question about which engine parameters are recommended by the FDR and what is the sample rate.
Hopefully you might be able to answer this.
Many thanks.
I am a retired gas turbine engineer who worked on safety systems and assessments and assisted on a number of accident investigations (military fast jets) and would be interested to know this.

I'm pretty convinced that everyone is watching different videos, which wouldn't surprise me in the least given how much images and footage can get mangled from being downloaded/re-uploaded to different services. Personally I've seen at least two different videos (and slightly different variants of each): one that's a direct recording of the aircraft and one that's a recording of a phone playing a recording of the aircraft. The buzz of a propeller was quite audible in the former but not in the latter, and the engines are notably quiet compared to any 787 takeoff I've ever been close to.

I do think that at this point people are working backwards from the cause being retracting the flaps, rather than working forwards from the evidence towards an explanation. If everything else was as it should be apart from flaps being retracted instead of gear, you'd at the very least expect the aircraft to reach a higher speed than is suggested by how little distance there is between the end of the runway and the crash site. Coupled with the apparently parabolic trajectory seen in the airport CCTV video, the crew (allegedly) reporting engine problems on the radio, the surviving passenger testifying about flickering cabin lights, the plausible deployment of the RAT, the fact that the ADS-B data cuts out well before impact...surely at some point one must consider a lack of thrust, no matter how improbable. Recognising the what doesn't need a full thesis on the how .

I wonder if (given all the facts and rumours about the situation so far) the flaps would be so high on everyone's minds if they weren't already a hot topic from the initial, largely baseless speculation that they somehow took off with flaps retracted.

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.

The nose gear angle suggest that the "gear-up" was selected and a dual engine failure happened at the same time, with the hydraulics failing and possible RAT deployment.. The APU was not running and everything, except the flight recorders, might be powered down and restarted at a very low altitude.

Very scary.

Can I just clarify: the 787 has FBW and certain flight envelope protections. If the pilots suffered a dual engine failure after takeoff, they would pull back to stretch the glide as the computers will not allow the aircraft to stall. This is effectively what Sully did when he kissed it into the Hudson like a pro.

In any other aircraft, if you lose thrust in all your engines, you would be pushing the nose down immediately!

I have now watched a number of "normal" 787 takeoffs online and in none of them does the gear go up super early, certainly not before the 10 seconds or so where this one seems to loose power. I think the flap/gear raising is wrong personally

I'm really trying to resist engaging here, but anyone who states what pilots, 'would', do in a given situation, simply hasn't grasped the most elementary, 1.01, fundamentals of human behaviour.

Again and again, I've listened to CVRs, or looked at FDR plots, or sat next to people in a flight deck or crew room, or restaurant, or anywhere (but especially in the back of a simulator)... and pondered what on earth led competent individuals to do what I had just witnessed. Of course, if the individuals aren't competent to start with (and that is NOT directed at this crew, but embellishes my point) there may be less mystery.

Also worth remembering, for those of us who do, the ludicrous training delivered by Airbus on the A320 family at the start, when they told people that, (a) pulling the stick back and holding it there will save you, and, (b) you don't need unusual attitude training in an FBW aircraft. I think we know how that played out. I'll add an element of my briefing for a departure in a single-engined aircraft, if a forced landing was not an option (eg Rochester, Biggin Hill), which also covers what I have always thought I would do faced with total power loss in a bigger machine, 'I will manoeuvre the aircraft to hit the softest thing I can, as slowly as possible'. Very glad I never had to see that through.

Regardless of FBW on the Boeings the pilot can stall the aircraft. The 787 and 777 don't have hard protection like the Airbus. You will get force feedback as you approach the stall, but keep pulling on the yoke and the plane will stall.

Which is why the aircraft flew a very sweet descent, nose up, increasing pitch until the Stall.

The only thing that could cause me to touch anything at that altitude is if they had already had a dual engine failure, which becomes a circular argument.

In the take off video I think there is a subtle yaw to the right at lift off (the moment it begins being obscured by the building in the foreground). There is then a massive blast of dust on the airfield on the left side of the aircraft as it lifts off. Later video audio suggests the engines were not at full power ( or even operating - just wind noise) and that the RAT was whirring. It also shows the fuselage wheel bogies were tilted forward - so wheels up has commenced - but the gear doors are not open.

Possible sequence: right engine failure at rotation, firewalling of left engine, lift off and positive rate, gear up lever activated, wheels tilt forward, left engine failure, RAT deployed, insufficient hydraulics to Open gear doors to complete gear up sequence, ongoing dual engine failure?

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.

The recordings are simply of too low quality to draw any conclusions from.

If it was dual engine failure shortly after rotation, that is very bad luck and I doubt any crew could recover from something like that.

I could speculate further but I think it\x92s just too hard to say without better quality footage or FDR data.

very bad luck, or a common root cause. It remains to be seen.

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?

Reports say that one of the black boxes have been recovered and the search continues for the other one. Apparently the B787 flight recorders log voice as well as data so only one is suffice if not damaged.

Speaking as a B787 Captain..... There is so much rubbish and stupid suggestion being written here.

This aircraft was airborne for a grand total of 22 seconds, half of which was climbing to no more than 150' aal.

- No Flaps? Due to the setup of the ECL it is physically impossible to go down the runway without some sort of take-off flap set. The T/o config warning would have been singing it's head off. Despite assertions to the contrary I have seen no video clear enough to detect a lack of flaps.

- RAT out? Almost impossible, I have seen no quality footage that definitively witnesses the RAT being out. Those who think they car hear a RAT type noise might be listening to a motorcycle passing or similar. It takes a triple hydraulic failure or a double engine failure to trigger RAT deploment. They happily went through V1 without a hint of rejected take off so as they rotated the aircraft was serviceable. These are big engines, they take a long time to wind down when you shut them down. I have never tried it however engine failure detection takes 30s or for the aircraft to react and they were not even airborne that long.
- Flaps up instead of gear? The B787 flaps are slow both in and out. Given that the 'Positive rate' call is not made the second the wheels leave the ground, a mis-selection of flaps up would not cause any loss of lift for at least 20 seconds, by which time they had already crashed. I believe the gear remained down not because of mis-selection but because of a major distraction on rotate.

Discounting the impossible, two hypotheses remain:

1. Invalid derate set through incorrect cross-checking. Trundling down the runway takes very little power to reach Vr. It is only when you rotate that you create more drag and discover that you do not have sufficient thrust vs. drag to sustain a climb. Or....
2. Put 200' as the altitude target in the FCU. Immediate ALT capture and all the power comes off. PF is still hand flying trying to increase pitch but is already way behind the aircraft.

It could be after this that Boeing are forced to review the B787 practice of exploring the very edges of the performance envelope.