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Europa01
2025-06-12T14:54:00 permalink Post: 11899298 |
Loss of Thrust
Subjects: None 1 user liked this post. |
Europa01
2025-06-13T09:50:00 permalink Post: 11900266 |
Mayday Message
Possibly the Captain did correctly perceive the information on the status of the aircraft Possibly he did correctly comprehend the situation. Possibly he did project the situation into the future (Endsley &Jones) Subjects: Mayday 1 user liked this post. |
Europa01
2025-06-13T21:33:00 permalink Post: 11900930 |
Cutoff Switches
Subjects: Flap Retraction Flaps (All) |
Europa01
2025-06-14T08:58:00 permalink Post: 11901279 |
wonkazoo #963
Thank you for such a clearly reasoned and thoughtful post. Taken together with
Capn Bloggs
\x92 reasoning on thrust levers in his #955 I\x92d like to think that pet theories would be tested against these two posts from this point onwards before hitting the keyboard (although I suspect they won\x92t be)
Last edited by Europa01; 14th Jun 2025 at 22:06 . Subjects: None |
Europa01
2025-06-16T08:03:00 permalink Post: 11903225 |
TCMA / FADEC
Repeating myself (again), but ALL the TCMA logic is resident in the FADEC. It takes aircraft inputs of air/ground (again, not familiar with the specifics of the air/ground logic used on the 787/GEnx-1B, so don't ask), thrust lever position, and what the engine is actually doing (mainly N1) to determine if the engine is 'out of control'.
The thrust lever inputs are hardwired (resolvers connected to the thrust levers, powered by the FADEC), other aircraft communications on the 787 are on an ethernet based network. Default mode for the FADEC if aircraft inputs are lost or invalid is "Air", as that is generally considered to be the 'safe' choice. But even assuming some aircraft fault caused the FADECs to falsely believe the aircraft was 'on-ground', it would still take a pretty major error in the TCMA logic for it to actually trigger and shutdown the engine (especially lacking an associated thrust lever movement to idle). Never say never, but we're getting pretty far out on the probability tree for all these things to happen. Then, ask yourselves which extraordinarily low probability bundle of previously unrevealed faults could spontaneously manifest themselves on both engines simultaneously. Also ask yourselves why these faults manifested at that critical phase of flight and not during taxiing or take-off roll when some of the TCMA sensors would have been primed. Subjects: Dual Engine Failure Engine Failure (All) FADEC TCMA (Air-ground Logic) TCMA (All) TCMA (Logic) Takeoff Roll 2 users liked this post. |
Europa01
2025-06-16T08:42:00 permalink Post: 11903262 |
There is so much wrong with this, I don't know where to start. First off, how about the PF saying "WTF, you've got the flaps, put them back out and pull the GEAR up!". Do you seriously think a professional crew are just going to sit there, do nothing and crash after the PNF selected the flaps and not the gear? In any case, during the descent, the video clearly shows the slats are extended. I very much doubt that the jet would fall out of the sky with two engines running just because the TE flaps went from 5\xb0 to 0\xb0 with the slats remaining extended.
Also please read the good Captain’s much earlier post along the lines of - if thrust runs back to idle wouldn’t the PF / PM simply advance the thrust levers to firewall? (Bloggs Test 2) Last edited by Europa01; 16th Jun 2025 at 08:53 . Subjects: None 6 users liked this post. |
Europa01
2025-06-13T09:50:00 permalink Post: 11903690 |
Mayday Message
Possibly the Captain did correctly perceive the information on the status of the aircraft Possibly he did correctly comprehend the situation. Possibly he did project the situation into the future (Endsley &Jones) Subjects: Mayday |
Europa01
2025-06-16T08:03:00 permalink Post: 11903748 |
TCMA / FADEC
Repeating myself (again), but ALL the TCMA logic is resident in the FADEC. It takes aircraft inputs of air/ground (again, not familiar with the specifics of the air/ground logic used on the 787/GEnx-1B, so don't ask), thrust lever position, and what the engine is actually doing (mainly N1) to determine if the engine is 'out of control'.
The thrust lever inputs are hardwired (resolvers connected to the thrust levers, powered by the FADEC), other aircraft communications on the 787 are on an ethernet based network. Default mode for the FADEC if aircraft inputs are lost or invalid is "Air", as that is generally considered to be the 'safe' choice. But even assuming some aircraft fault caused the FADECs to falsely believe the aircraft was 'on-ground', it would still take a pretty major error in the TCMA logic for it to actually trigger and shutdown the engine (especially lacking an associated thrust lever movement to idle). Never say never, but we're getting pretty far out on the probability tree for all these things to happen. Then, ask yourselves which extraordinarily low probability bundle of previously unrevealed faults could spontaneously manifest themselves on both engines simultaneously. Also ask yourselves why these faults manifested at that critical phase of flight and not during taxiing or take-off roll when some of the TCMA sensors would have been primed. Subjects: Dual Engine Failure Engine Failure (All) FADEC TCMA (Air-ground Logic) TCMA (All) TCMA (Logic) Takeoff Roll 1 user liked this post. |
Europa01
2025-06-16T08:03:00 permalink Post: 11903688 |
TCMA / FADEC
Repeating myself (again), but ALL the TCMA logic is resident in the FADEC. It takes aircraft inputs of air/ground (again, not familiar with the specifics of the air/ground logic used on the 787/GEnx-1B, so don't ask), thrust lever position, and what the engine is actually doing (mainly N1) to determine if the engine is 'out of control'.
The thrust lever inputs are hardwired (resolvers connected to the thrust levers, powered by the FADEC), other aircraft communications on the 787 are on an ethernet based network. Default mode for the FADEC if aircraft inputs are lost or invalid is "Air", as that is generally considered to be the 'safe' choice. But even assuming some aircraft fault caused the FADECs to falsely believe the aircraft was 'on-ground', it would still take a pretty major error in the TCMA logic for it to actually trigger and shutdown the engine (especially lacking an associated thrust lever movement to idle). Never say never, but we're getting pretty far out on the probability tree for all these things to happen. Then, ask yourselves which extraordinarily low probability bundle of previously unrevealed faults could spontaneously manifest themselves on both engines simultaneously. Also ask yourselves why these faults manifested at that critical phase of flight and not during taxiing or take-off roll when some of the TCMA sensors would have been primed. Subjects: Dual Engine Failure Engine Failure (All) FADEC TCMA (Air-ground Logic) TCMA (All) TCMA (Logic) Takeoff Roll |
Europa01
2025-06-16T08:42:00 permalink Post: 11903689 |
There is so much wrong with this, I don't know where to start. First off, how about the PF saying "WTF, you've got the flaps, put them back out and pull the GEAR up!". Do you seriously think a professional crew are just going to sit there, do nothing and crash after the PNF selected the flaps and not the gear? In any case, during the descent, the video clearly shows the slats are extended. I very much doubt that the jet would fall out of the sky with two engines running just because the TE flaps went from 5\xb0 to 0\xb0 with the slats remaining extended.
Also please read the good Captain’s much earlier post along the lines of - if thrust runs back to idle wouldn’t the PF / PM simply advance the thrust levers to firewall? (Bloggs Test 2) Subjects: None 1 user liked this post. |
Europa01
2025-06-19T16:05:00 permalink Post: 11906149 |
Cutoff Switches
this isn’t the type of switch fitted to the 787 as a fuel control switch, totally irrelevant but has generated yet more nonsense. The switches are spring loaded (or so it feels) in addition to having a massive block to prevent inadvertent operation in either direction. Anyone suggesting they could be accidentally “knocked off” is so clueless about their operation it’s actually painful to rebut
Not looking over my shoulder here but I should add that I know and respect Honeywell switches. Those I have worked with are well designed and well made plus Honeywell incorporate improvements based on field experience. As posted by another contributor upthread I am puzzled by the odd ‘down’ = engine off configuration though. Last edited by Europa01; 19th Jun 2025 at 16:36 . Subjects: Fuel (All) Fuel Cutoff 4 users liked this post. |
Europa01
2025-06-20T13:25:00 permalink Post: 11906973 |
TCMA
And each FADEC is unique to the engine in which it is hosted. So whilst these may be "autonomous" they still rely on data external to the engine itself such as WoW and Rad Alt where they hold more "sway" than they do in the flight deck.
Are these values recorded in the FDR? Are values from the FADEC recorded? I’d like to add a complimentary test to user989’s logic on TCMA faults. Regardless of whether the ‘aircraft on ground’ signal was incorrect after rotation it would have been correct during the takeoff roll. IF there was an unrevealed fault in a thrust lever position signal THEN why didn’t TCMA activate during taxiing or the takeoff roll? Such a fault occurring spontaneously in just the few seconds after rotation is way way down the probability table. Such a fault occurring spontaneously on both separate (think ETOPS) engine control systems is surely vanishingly unlikely. They may be out there but you’d have to ask if TCMA is implicated where are the lower consequence precursor events in the 787 fleet? These might be spurious TCMA action on one engine or faults with ‘aircraft on ground’ found during maintenance or engines not responding to thrust lever position and so on. Change Analysis would ask what happened differently in the few seconds after rotation on this flight that separates it from all other 787 takeoffs and why at that particular time ?The interim report will provide some answers until then please let’s confine this thread to fact based technical discussion and debate. Re-reading this I did briefly consider suggesting engine overshoot of thrust lever positions and FADEC shut down on N1 overspeed but that leaves a lot of WHY and WHY both engines questions so I dismissed it. Subjects: FADEC FDR TCMA (All) Takeoff Roll 3 users liked this post. |
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