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Screamliner
2025-06-15T08:58:00 permalink Post: 11902261 |
So one thing to keep in mind, the RAT can be deployed manually, but also comes automatically when certain conditions arise, everybody here is assuming it\x92s only on dual engine failure but there are 4 more conditions that trigger the RAT,
- all three hydraulic system pressures are low - loss of all electrical power to the captain and first officers flight instruments - loss of all four EMP\x92s (electro motor driven pump) and faults in the flight controls system occur during arrival - loss of all four EMP\x92s and an engine fails during take off. This all comes directly from B787 FCOM, If we assume that what our survivor saw is correct, maybe it was an electrical failure, the aircraft had electrical issues in Delhi during departure and I checked the crash video again, I don\x92t see the strobe lights (neither wing or tail) and also no Anti collision light either. this might also explain the self starting APU on loss of the electrics (engine driven generators). That could also result in a loss of situational awareness with the speed, because of no indication, even the HUD would not work. The mayday call would still be doable because the radios work from the battery. |
guided
2025-06-15T09:11:00 permalink Post: 11902270 |
Can we focus on theories explaining the facts? Specifically:
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Axel-Flo
2025-06-15T09:16:00 permalink Post: 11902273 |
Perceived double engine failure
I saw earlier someone post about this and wondered how the drill would run and how/who performed memory items. On a past 4 jet type a double engine failure drill was done in the sim regularly and both had immediate actions as well as a number of confirmations but at least we still had two running😎. In this scenario of a twin jet where perhaps the PF noticed a major loss of thrust and called \x93Double engine failure drill\x94 would PNF confirm it then do the 2 switches and hit the guarded RAT button without identification and confirmation or is it whoever gets there first? Seems a free for all scramble would be a poor way to do it since latched and guarded switches could be operated incorrectly in a panic without deliberate and controlled movement backed up by confirmation of diagnosis and then the memory items?
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1stspotter
2025-06-15T09:25:00 permalink Post: 11902276 |
Can we focus on theories explaining the facts? Specifically:
12 users liked this post. |
sorvad
2025-06-15T09:56:00 permalink Post: 11902306 |
(Sorry, Airbus here and not familiar with Boeing) Flap 5 to 1 reduction on the Boeing triggers autothrust reduction, is that correct? If so, are there any other conditions that need to be met for this to happen like being in some kind of takeoff mode? Just thinking whether this would have potential otherwise in other regimes to cause issues, discontinued approach perhaps.
Am slightly puzzled as to why if flap reduction triggering climb thrust is part of the standard logic (and presumably clean-up technique) then partial dual thrust loss wouldn’t be immediately recognised as the classic symptom of gear / flap retraction handling error? I presume Boeing pilots / air India are just as aware of this it as everyone else, strikes me as odd that one would immediately go into full dual EF mode. My instinctive reaction without knowing the Boeing would be to firewall both TLs, would this have worked in the early flap retraction logic scenario? Many thanks all Last edited by sorvad; 15th Jun 2025 at 10:15 . 6 users liked this post. |
Travis Anderson
2025-06-15T09:59:00 permalink Post: 11902310 |
In less than a month we'll have a preliminary report. Last edited by T28B; 15th Jun 2025 at 13:00 . Reason: brackets completed |
SteinarN
2025-06-15T11:54:00 permalink Post: 11902404 |
It could do it, assuming fuses/contactors didn't vapourise first.
I expect the VFSG shafts would be designed to fuse/slip long before the main radial shaft feeding the gearbox, as noted. But if it occurred, it would knock out not just your FADEC alternator but also the high pressure fuel pumps. Engine would stop dead near instantly. It would partly be a question of how much interlocking is present. I guess bypassing/mis-adjusting mechanical interlocks is something poor maintenance could & would do. Online/running generators connected together by accident/fault will cause a HUGE load on everything, electric connections, generator itself and the shafts and gears driving the generators. Heck, I wouldnt be surprised if the generator could disintegrate due to such an electromagnetic shock load. So, the question is if there is something between the generators that could limit the electric current. A VFD possibly would as the VFD maybe would not be able to pass the current required for shearing the drive shaft for example. But then again, electronic switches like IGBT/MOSFET and such are able to pass an incredibly large over current for some milliseconds before exploding. Possibly 50 to 100 times the nominal current. So I am not sure if a VFD really would save the rest of the system in a situation with two generators connected together in error. So, where is the VFD part installed, directly on each generator or somewhere else in the system? Are there physical interlocks on the contactors or only electric interlocks? 2 users liked this post. |
Captain Fishy
2025-06-15T12:00:00 permalink Post: 11902407 |
What if the PF called stop just before V1and closed the thrust levers but either changed his mind or was overridden by the other pilot, who rapidly pushed the thrust levers back up. Could this trigger a TCMA intervention and subsequent dual engine shutdown as it was still on the runway at this point? Hopefully not.
2 users liked this post. |
mechpowi
2025-06-15T12:38:00 permalink Post: 11902430 |
What if the PF called stop just before V1 and closed the thrust levers but either changed his mind or was overridden by the other pilot, who rapidly pushed the thrust levers back up. Could this trigger a TCMA intervention and subsequent dual engine shutdown as it was still on the runway at this point? Hopefully not.
It also doesn\x92t explaine the ADS-B data showing acceleration after lift off. 1 user liked this post. |
island_airphoto
2025-06-15T13:17:00 permalink Post: 11902459 |
Maybe a dumb question - A DA-42 went in with double engine failure when the gear was retracted, the additional load of the gear pump was enough to drop the bus voltages low enough to shut down both FADECs. They took off with a very low battery and no one had tested this scenario previously. Obviously a very different airplane, but still raising the gear probably is a significant load and may have caused an electrical problem to get worse.
* or Boeing thought of that, DA-42s got rewired and won't do that now. 1 user liked this post. |
Pelican
2025-06-15T13:21:00 permalink Post: 11902462 |
Trying to keep an open mind, but….
Is no one surprised the lone survivor remembers a bang just before impact, and other things like apparently emergency lights, but has not mentioned the power going from takeoff power to nothing. Even the power change at thrust reduction altitude is often very noticeable in the cabin, so it surprises me nothing about the noise (and startle/panic) of full-power to no-power has been mentioned. I think we are getting into absurd scenarios trying to make the scenario of a simultaneous double engine failure just after liftoff fit, based on perhaps not the best evidence. 1 user liked this post. |
LTC8K6
2025-06-15T13:23:00 permalink Post: 11902467 |
Trying to keep an open mind, but\x85.
Is no one surprised the lone survivor remembers a bang just before impact, and other things like apparently emergency lights, but has not mentioned the power going from takeoff power to nothing. Even the power change at thrust reduction altitude is often very noticeable in the cabin, so it surprises me nothing about the noise (and startle/panic) of full-power to no-power has been mentioned. I think we are getting into absurd scenarios trying to make the scenario of a simultaneous double engine failure just after liftoff fit, based on perhaps not the best evidence. |
galaxy flyer
2025-06-15T13:24:00 permalink Post: 11902470 |
Maybe a dumb question - A DA-42 went in with double engine failure when the gear was retracted, the additional load of the gear pump was enough to drop the bus voltages low enough to shut down both FADECs. They took off with a very low battery and no one had tested this scenario previously. Obviously a very different airplane, but still raising the gear probably is a significant load and may have caused an electrical problem to get worse.
* or Boeing thought of that, DA-42s got rewired and won't do that now. |
JG1
2025-06-15T13:30:00 permalink Post: 11902476 |
A little bit tangential here, thinking about this Mayday call (the exact contents of which haven't been verified, but have been variously reported as "no power", or "lost power" ) , if in front of you on the PFD, in large red letters, you have the words ENG FAIL, why would you say, "no power"? Seems a bit strange. Why not say "engine failure" or "no thrust"?
Could it be that "No power" may have meant the whole cockpit went dark? ie. A total electrical failure or huge short (survivor's bang) initiating RAT deployment and apu autostart. Doesn't explain loss of thrust explicitly but if there was a massive electrical issue, and critical data was lost (thinking air/ground switch position and other fundamentals), would dual engine shutdown be a possibility? Simultaneous FADEC failure? Exceptionally remote possibility perhaps, but by definition these accidents are exceptionally remote. If the RAT deployed we know there was definitely an electrical issue - how bad was it, though? Thinking about the possibility of an electrical failure causing an engine (and instrumentation) failure rather than the other way around. Over to the experts on this. Last edited by JG1; 15th Jun 2025 at 14:20 . |
OldnGrounded
2025-06-15T13:34:00 permalink Post: 11902477 |
Trying to keep an open mind, but\x85.
Is no one surprised the lone survivor remembers a bang just before impact, and other things like apparently emergency lights, but has not mentioned the power going from takeoff power to nothing. Even the power change at thrust reduction altitude is often very noticeable in the cabin, so it surprises me nothing about the noise (and startle/panic) of full-power to no-power has been mentioned. I think we are getting into absurd scenarios trying to make the scenario of a simultaneous double engine failure just after liftoff fit, based on perhaps not the best evidence. 1 user liked this post. |
Icarus2001
2025-06-15T13:42:00 permalink Post: 11902480 |
Could it be that "No power" may have meant the whole cockpit went dark? ie. A total electrical failure, initiating RAT deployment and apu autostart. Doesn't explain loss of thrust explicitly but if there was a massive electrical issue, and critical data was lost (thinking air/ground switch position and other fundamentals), would dual engine shutdown be a possibility? Simultaneous FADEC failure? Exceptionally remote possibility perhaps, but by definition these accidents are exceptionally remote. Over to the experts on this.
The engines will just keep running despite total electrical failure. FADEC units are self powered and independent. Even a completely “dark” flight deck still has the ISIS. 3 users liked this post. |
Someone Somewhere
2025-06-15T13:43:00 permalink Post: 11902481 |
Sorry I am not a pilot but I did spend three years filming a TV series at Boeing for pBS/Channel 4 about the design and construction of the 777, and my response is not a technical one anyway. Do airfields have high definition video coverage of all takeoffs and landings? If so, they should be public domain and there would not be hundreds of posts about grainy over-magnified smartphone footage. If they don't, a 6-cam setup on each runway (3 either side of runway, one back, one across and one forward) could record continuously to hard disk or cloud. If airfields don't have this, shouldn't it be made mandatory?
I have been really wondering what single point of failure could take out both engines simultaneously as seems to be the case here. One single main bus contactor closing in error seems to possibly be such a single point fault.
Online/running generators connected together by accident/fault will cause a HUGE load on everything, electric connections, generator itself and the shafts and gears driving the generators. Heck, I wouldnt be surprised if the generator could disintegrate due to such an electromagnetic shock load. So, the question is if there is something between the generators that could limit the electric current. A VFD possibly would as the VFD maybe would not be able to pass the current required for shearing the drive shaft for example. But then again, electronic switches like IGBT/MOSFET and such are able to pass an incredibly large over current for some milliseconds before exploding. Possibly 50 to 100 times the nominal current. So I am not sure if a VFD really would save the rest of the system in a situation with two generators connected together in error. So, where is the VFD part installed, directly on each generator or somewhere else in the system? Are there physical interlocks on the contactors or only electric interlocks? VFDs are for frequency conversion to drive the motors (CAC/pumps/engine start). They won't be carrying the full generator load for galleys and anti-ice; that will be handled by cross-ties, which is a big black box on the 787. Fast fuses can be faster acting than circuit breakers, but are one-shot. I'm not sure how fast-acting and effective the generator contactors/controllers are; conventional ACBs/MCCBs will blow open magnetically under sufficient fault current regardless of what the trip unit or close coil commands. I wouldn't really expect electrical reconfiguration to happen on climbout, and I wouldn't expect it to be the first time this contactor gets used since maintenance - everything should get a good workout during sequential APU/engine starts.
No system would be designed to parallel two frequency wild generators. The output from each would be rectified to dc and conditioned before application to the load, but could be paralleled at dc level if required for redundancy. These are quarter megawatt generators, where an out of phase connection could shear drive shafts, destroy the drive train, or worse.
In a very simple main-tie-main arrangement you can close any two of three breakers and still keep the sources separate. It gets much more complicated when you have ten different sources. I suspect the 'large motor power centre' might parallel the rectified output of some generators.
I no longer believe in the no flaps / flaps raised early theory.
I think this was a major electrical failure most likely due to the engines quitting. The 787 is far more heavily dependent on electrical power to run it's systems than previous Boeing planes. It requires about 1.5 megawatts of power according to Wiki. 5X more than previous designs. Things that were done by engine driven pumps/compressors and engine bleed air are all done electrically on the 787. Flight controls that were moved hydraulically or pneumatically are moved by electric actuators. Etc. 1.5MW is the figure for all six generators; only four can be used at once. There's no indication they had any flight control issues.
Seems to be funny that no-one has mentioned the Battery, which because of its age could have failed either Short-circuit or Open-circuit.
Maybe some Boeing Electro Techs, could explain what role the battery has in this circumstance. The simultaneous failure of both engines points towards an electrical problem, unless the high temperature had adversely affected the fuel flow. 1 user liked this post. |
EGPI10BR
2025-06-15T14:27:00 permalink Post: 11902507 |
A little bit tangential here, thinking about this Mayday call (the exact contents of which haven't been verified, but have been variously reported as "no power", or "lost power" ) , if in front of you on the PFD, in large red letters, you have the words ENG FAIL, why would you say, "no power"? Seems a bit strange. Why not say "engine failure" or "no thrust"?
Could it be that "No power" may have meant the whole cockpit went dark? ie. A total electrical failure or huge short (survivor's bang) initiating RAT deployment and apu autostart. Doesn't explain loss of thrust explicitly but if there was a massive electrical issue, and critical data was lost (thinking air/ground switch position and other fundamentals), would dual engine shutdown be a possibility? Simultaneous FADEC failure? Exceptionally remote possibility perhaps, but by definition these accidents are exceptionally remote. If the RAT deployed we know there was definitely an electrical issue - how bad was it, though? Thinking about the possibility of an electrical failure causing an engine (and instrumentation) failure rather than the other way around. Over to the experts on this. Misty. 1 user liked this post. |
Screamliner
2025-06-15T15:11:00 permalink Post: 11902541 |
I'm reading a lot of the comments, speculation is something we all like, but some things just do not add up, even with a RAT deployed
if they had dual engine failure around 50 feet where you raise the gear, how can they still find the energy to climb, since they would be at VR/V2 speed (not V2+20 at that altitude, what VNAV would command after take off, especially with a take off weight of around 205/210 tons, the 787 wings are amazing but not miracles if they had a normal departure, why did they not raise the gear, they had a positive rate since they were climbing and the speed according to ADS-B was a constant. if they were single engine ! this would have saved them with this weight and weather, one of the first things you learn when EFATO with a 787, raise the gear, your climb performance increases dramatically Intersection take off can be ruled out: if they did an intersection departure with they're genex 64-70K engines, they would have had a take off limited weight of around 172 tons, I estimate that they were close to 205/210 tons, (max zfw of around 161 tons and around 45/50 tons of fuel) even full length would have been a stress for the engines, with the prevailing weather conditions, they would have never made it, full length is already difficult. When we see the video, the airplane is still climbing / flying straight and level (not losing altitude), yet we hear what we think might be the RAT, I can't imagine that they had the kinetic energy to do this with no engines. if they had dual engine failure, they would have been a brick, Hot and High, no thrust, flaps 5, zero chance. flickering of lights etc. seen by the survivor and the loud bang heard, I would not trust pax observations, because of the things they had to go through, also and I've said this before, if it was a loud bang, where is the smoke and fire in the engines, or in the video, its not audible lets see what the report will say, but it it could be a lot to swallow for some Last edited by T28B; 15th Jun 2025 at 16:30 . Reason: cleaned up formatting 1 user liked this post. |
OPENDOOR
2025-06-15T16:06:00 permalink Post: 11902592 |
Trying to keep an open mind, but\x85.
Is no one surprised the lone survivor remembers a bang just before impact, and other things like apparently emergency lights, but has not mentioned the power going from takeoff power to nothing. Even the power change at thrust reduction altitude is often very noticeable in the cabin, so it surprises me nothing about the noise (and startle/panic) of full-power to no-power has been mentioned. I think we are getting into absurd scenarios trying to make the scenario of a simultaneous double engine failure just after liftoff fit, based on perhaps not the best evidence. ​​​​​​​ 2 users liked this post. |
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