2025-06-14T19:26:00
permalink Post: 11901751
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.
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.
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.
Subjects: Dual Engine Failure Engine Failure (All) Flap Retraction Flaps (All) Fuel (All) Fuel Cutoff Gear Retraction RAT (All) RAT (Deployment) RAT (Sound)
2025-06-14T19:44:00
permalink Post: 11901765
Even my very experienced planespotter friends agree with me that it'd be very hard to notice from the ground even with bino's, let alone grainy footage. The B787/788's flaps are so well integrated you can hardly spot the difference if you're not sitting right next to them already.
Now I'm curious of the mechanical switchover mechanism that prevents backtracking of the flaps in the event the hydraulics fail and pressure drops which would slowly retract the flaps as hydraulic fluid drains from the pressure reservoir.
Now I'm curious of the mechanical switchover mechanism that prevents backtracking of the flaps in the event the hydraulics fail and pressure drops which would slowly retract the flaps as hydraulic fluid drains from the pressure reservoir.
Subjects: Hydraulic Failure (All)
2025-06-14T19:55:00
permalink Post: 11901777
Climb Power is programmed as an altitude in the FMC, usually 1000' but sometimes higher for noise abatement, which in this case they wouldn't have reached.
In some instances, the TO derate is so significant that the selection of climb power moves the thrust levers forward. AMD is sea level with a long runway, so can imagine it would be a fairly low power take off.
In some instances, the TO derate is so significant that the selection of climb power moves the thrust levers forward. AMD is sea level with a long runway, so can imagine it would be a fairly low power take off.
And yes with a takeoff with heavy derates CLB might be more than selected for TO (although IIRC CLB2 usually wasn`t when we were using TO2 with moderate AT).
Understand it`s a long runway but I wouldn’t assume heavy derates with a moderately long flight and full airplane (and hot day). But we don`t know yet.
Subjects: Flap Setting Flaps (All)
2025-06-14T20:11:00
permalink Post: 11901792
I\x92m now convinced the whole \x91mis-selected flaps\x92 is a complete red herring. Based on the wreckage on the ground which clearly showed the flaps extended and a still from the witness video which I am 100% sure shows the flaps extended. I always believed it was a total loss of thrust and now can\x92t see any other explanation and so need to know why that happened.
Accident aircraft with TE flaps visible.
\x91Normal\x92 787 takeoff with flaps
Accident aircraft with TE flaps visible.
\x91Normal\x92 787 takeoff with flaps
But if the TE flaps were down in TO position in the wreckage pic (haven`t seen it) that`s that.
Subjects: None
4 users liked this post.
2025-06-14T22:45:00
permalink Post: 11901916
We`ll just have to wait a bit until some facts come out.
Not ready to shelve the flap/RTOW probability quite yet.
Or even deliberate (or inadvertent) actuation of the FCSs. Incapication, etc.
Subjects: Dual Engine Failure Electrical Failure Engine Failure (All)
2 users liked this post.
2025-06-15T11:32:00
permalink Post: 11902384
So for those getting in the weeds with one in several trillion (or lower) probabilities of systems failures have you considered that that improper RTOW (with or without improper flap setting), flap retraction / climb thrust trigger, is of much higher probability and has actually happened ?
Anyway I think we’ll find out soon if a systems failure was involved.
The FLCH Hold thing (Asiana) was never an issue and well known (at least on our line). And for a crew of 3 (or 4) to press a destabilized approach getting 40-ish knots too slow (!) isn’t a systems problem — it’s a breach of basic airmanship.
Anyway I think we’ll find out soon if a systems failure was involved.
The FLCH Hold thing (Asiana) was never an issue and well known (at least on our line). And for a crew of 3 (or 4) to press a destabilized approach getting 40-ish knots too slow (!) isn’t a systems problem — it’s a breach of basic airmanship.
Last edited by Senior Pilot; 15th Jun 2025 at 11:49 . Reason: Edit
Subjects: Flap Retraction Flap Setting Flaps (All)
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2025-06-15T15:32:00
permalink Post: 11902560
I do concur if it was a major systems breakdown without crew mistakes being made we will know shortly through emergency ADs.
Subjects: APU Gear Retraction
2025-06-17T16:20:00
permalink Post: 11904438
In jet aircraft how many systems related dual engine flameouts have occurred at low altitude ? Excluding FOD \x97 birds and ice (which presumably aren\x92t a factor here) how many systems caused dual engine flameouts have occurred ?
As opposed to how many engine failures, thrust losses, or shutdowns have been caused by crew members grabbing at improper levers under stress or setting wrong data (I\x92ll include Air Florida in that).
Not meant to be self - indicting by any means but if one is looking at probabilities and far-fetched scenarios you can\x92t exclude crew actions as a part of that.
Subjects: EDML
4 users liked this post.
2025-06-17T16:26:00
permalink Post: 11904447
I'm afraid that this reconstituted thread is more polluted worse than the original as mods try to hold back this flood of sewage. While there are multiple examples of air disasters caused solely by astonishingly egregious malfeasance by pilots, I see absolutely no point in unsupported speculation about such things. I can't ever say "no professional aircrew would ever do that" but spouting off random theories with no evidence and no practical experience or knowledge of the actual operations involved is really annoying and pointless. If you are a GA pilot, SLF with an engineering degree or a sim enthusiast then maybe, just maybe, you can manage to ask an intelligent question--preferrably one that hasn't already been asked and answered five times already. But please keep your inane hypotheses and conclusions to yourself for now.
There's no prize for guessing correctly!
Subjects: None
2 users liked this post.
2025-06-17T18:14:00
permalink Post: 11904530
In any case the autopilot wouldn\x92t have been in at such a low altitude and the PF would have been hand flying. Most of the min engagement altitudes for autopilots is 400\x92 AGL.
But again all of this is speculation in every way.
Subjects: None
2025-06-18T00:08:00
permalink Post: 11904784
One good thing from reading the full thread is I learned the 78 hydraulic system is essentially the same as the 777 !
While I appreciate the excellent analysis of some regarding the RAT I`m still not completely convinced of its deployment much less why it depoloyed. Sounds like the auto-deploy is identical to 777 (less the transfer bus deal which is replaced by the electrics on the 78 system), but it can be manually deployed as well by boinking the button.
I very much respect the survivors testimony. It will be very helpful. And all he went through. However, one must realize that under stress and injury (whether pilot or pax) ones memory is severely affected by physiological factors and retrograde symptoms of a traumatic event which varies by individual.
While I appreciate the excellent analysis of some regarding the RAT I`m still not completely convinced of its deployment much less why it depoloyed. Sounds like the auto-deploy is identical to 777 (less the transfer bus deal which is replaced by the electrics on the 78 system), but it can be manually deployed as well by boinking the button.
I very much respect the survivors testimony. It will be very helpful. And all he went through. However, one must realize that under stress and injury (whether pilot or pax) ones memory is severely affected by physiological factors and retrograde symptoms of a traumatic event which varies by individual.
Subjects: RAT (All)
2025-06-18T01:18:00
permalink Post: 11904818
I wouldn't be surprised.
The speed should be at least at V2 and probably higher. Why would the ATS not just hold that speed, albeit being a shock to the crew. Within a few seconds I'll bet the throttles would end up back in the forward position as the ATS says "hey, we're slowing down fast here!". It would be ugly but I can't see that the jet's going to drop out of the sky. The throttles aren't going to come right back and stay right back.
The speed should be at least at V2 and probably higher. Why would the ATS not just hold that speed, albeit being a shock to the crew. Within a few seconds I'll bet the throttles would end up back in the forward position as the ATS says "hey, we're slowing down fast here!". It would be ugly but I can't see that the jet's going to drop out of the sky. The throttles aren't going to come right back and stay right back.
From one of the previous scenarios if capture at a way low altitude occurred they`d (IIRC correctly) engage in SPD mode resulting in a significant loss of thrust as they attempted to maintain speed assuming a level off. Presumably after this when the PF continued a climb (regardless of flight director) they`d come forward after this loss of thrust to attempt to meet commanded speed—V2 or V2+15 or whatever—but there`d be a lag. But I`ve never misset the MCP to a way low altitude in flight or the sim (not a holier than thou thing) so I`m not entirely sure how how the autothrottles would behave.
More than one crew has failed to push them to the stops when things went south.
And the reverse is true; when the second MCAS accident happened IIRC the autothrottles stayed in THR REF due to task saturation by the crew. Exacerbating the condition and ultimately resulting in an accident.
3 users liked this post.
2025-06-18T01:31:00
permalink Post: 11904827
My comment was in relation to the scenario being discussed: a low-level level-off because the altitude selector was set properly before takeoff. And in any case, that Air India jet didn't look like it had climb thrust on as it topped out and started descending; it was pretty much gliding.
Never tried it so I`m not sure.
Subjects: None
2025-06-18T01:33:00
permalink Post: 11904829
Minimum autopilot engagement height on the B787 is 200'.
On the B787 if VNAV is engaged and the aircraft captures an altitude below the programmed acceleration height then the vertical mode transitions to VNAV ALT and commences acceleration to the current flap setting limit speed -5 knots.
On the B787 if VNAV is engaged and the aircraft captures an altitude below the programmed acceleration height then the vertical mode transitions to VNAV ALT and commences acceleration to the current flap setting limit speed -5 knots.
Subjects: Flap Setting Flaps (All) VNAV
2025-06-18T14:14:00
permalink Post: 11905284
Yes, we know it climbed. I suggested use of the granular data to show
how
high it was, in the context of the 400ft mode changeover point.
I don't have access to a current 787 manual, but have found a couple of unverified references to the VNAV engagement on the net. It appears the VNAV will engage at 400ft also. Happy to be corrected though.
Level-off point, approx 11sec after liftoff:
I don't have access to a current 787 manual, but have found a couple of unverified references to the VNAV engagement on the net. It appears the VNAV will engage at 400ft also. Happy to be corrected though.
Level-off point, approx 11sec after liftoff:
I never tried this in the sim on the 777 so I\x92m not sure. I was grateful that the 777 would change to SPD mode on initial altitude capture (as opposed to the -400 VMo here we go). It\x92s been a few years in any case though.
Subjects: VNAV
2025-06-18T14:49:00
permalink Post: 11905304
Subjects: VNAV
2025-06-18T17:38:00
permalink Post: 11905418
Usually on takeoff LNAV and VNAV are armed. During the takeoff roll the autothrottle system goes in to HOLD mode at 80kts.
At that point the FMAs read:
At 50' LNAV engages and the FMAs change to:
At 400' VNAV engages and the FMAs change to:
The height is referenced to a barometric snapshot taken during the take off roll at 100kts.
If an altitude is captured before VNAV engagement (totally bizarre to capture an altitude of less than 400') then the FMAs would change to:
SPD | LNAV | ALT
At that point the FMAs read:
At 50' LNAV engages and the FMAs change to:
At 400' VNAV engages and the FMAs change to:
The height is referenced to a barometric snapshot taken during the take off roll at 100kts.
If an altitude is captured before VNAV engagement (totally bizarre to capture an altitude of less than 400') then the FMAs would change to:
SPD | LNAV | ALT
Could explain the witnesses thought that power came back up before they hit but witness recollections post traumatic event as well as second hand reporting need some time to settle in before accurate facts come out.
Last edited by Shep69; 18th Jun 2025 at 17:53 .
Subjects: Takeoff Roll V2 VNAV
2025-06-19T01:08:00
permalink Post: 11905650
Non-aviation engineer here: I have a question about the low level altitude capture theory that I've been a bit hesitant to ask, since no-one else seemed to be bringing it up.
My understanding of altitude capture is that the autopilot will automatically adjust both thrust and pitch to intercept the requested altitude. However to my eyes there is very little pitch adjustment in the CCTV video of the plane taken from behind, until the very end of the video when it pitches up somewhat (obscured by buildings, more visible in the smartphone video). Please correct me if I'm wrong but I'd have thought that if the autopilot was trying to capture a very low altitude it would start pitching down (quite noticeably!) to do so, not remain at what looks like 10+ degrees nose-up. I honestly struggle to reconcile what I'm looking at in the video with an attempt to level off at 0ft, 200ft, or any of the other mentioned low-level altitudes.
Also maybe I'm missing something 787-specific but generally doesn't the autopilot have to be activated for the aircraft to automatically attempt to capture the pre-selected altitude? That was the case in this incident involving a Dash 8 and a target altitude of 0 feet that I am reading about ( https://www.gov.uk/aaib-reports/aaib...-dash-8-g-ecoe ). I'd have thought the PF would still be hand-flying the departure at the point that things went wrong, considering that the gear hadn't even been retracted yet...
My understanding of altitude capture is that the autopilot will automatically adjust both thrust and pitch to intercept the requested altitude. However to my eyes there is very little pitch adjustment in the CCTV video of the plane taken from behind, until the very end of the video when it pitches up somewhat (obscured by buildings, more visible in the smartphone video). Please correct me if I'm wrong but I'd have thought that if the autopilot was trying to capture a very low altitude it would start pitching down (quite noticeably!) to do so, not remain at what looks like 10+ degrees nose-up. I honestly struggle to reconcile what I'm looking at in the video with an attempt to level off at 0ft, 200ft, or any of the other mentioned low-level altitudes.
Also maybe I'm missing something 787-specific but generally doesn't the autopilot have to be activated for the aircraft to automatically attempt to capture the pre-selected altitude? That was the case in this incident involving a Dash 8 and a target altitude of 0 feet that I am reading about ( https://www.gov.uk/aaib-reports/aaib...-dash-8-g-ecoe ). I'd have thought the PF would still be hand-flying the departure at the point that things went wrong, considering that the gear hadn't even been retracted yet...
Minimum autopilot engagement altitude is 200\x92 for the 78 (from others on the forum). It\x92s 400\x92 AGL on the 777.
My interest is in how the auto throttles would have behaved in such a situation\x97where VNAV would not be engaged yet and the automatics gone into SPD/ALT. ; would they have pulled off thrust assuming a level off and then come back in to maintain bug speed (perhaps confusing the crew in the process ?).
1 user liked this post.
2025-06-20T13:55:00
permalink Post: 11906990
One fact that alters things substantially is whether the survivor's impression is correct that possibly the engines started to spool up again just before impact. If that's the case then what does that do to the possibility or otherwise that the TMCA system caused a dual engine shutdown?
There may have been other electrical and systems malfunctioning. But if whatever happened, let’s say the auto throttle simply pulled power to idle —or a low power setting—at a critical time. Perhaps on its own perhaps with other systems failures.
We like to think it basic that we’d slam the throttles forward. Right away.
But Asiana didn’t.
And neither did Air Florida years ago.
Subjects: Dual Engine Failure Engine Failure (All) Engine Shutdown
2025-06-20T18:17:00
permalink Post: 11907177
Best glide doesn't start until the aircraft reaches best glide speed. That might mean raising the nose to decelerate depending on the starting speed. Not saying this case was far above best gliding speed, but your statement assumes they were below best gliding speed.
Subjects: None
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