Posts about: "Dual Engine Failure" [Posts: 231 Pages: 12]

Screamliner
2025-06-15T08:58:00
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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
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Post: 11902270
Can we focus on theories explaining the facts? Specifically:
  • Aircraft used almost the whole runway (3500m)
  • Flaps found on the ground in setting 5
  • RAT deployed
  • Mayday that they lost power
this rules out flap up instead of gear up , selecting wrong autopilot setting, gear up causing electrical faults (as problems started earlier - using up all runway). Something must have happened on the runway (after v1?) that led to loss of electrics (and dual engine failure, maybe later?)


Axel-Flo
2025-06-15T09:16:00
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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?
1stspotter
2025-06-15T09:25:00
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Post: 11902276
Originally Posted by guided
Can we focus on theories explaining the facts? Specifically:
  • Aircraft used almost the whole runway (3500m)
  • Flaps found on the ground in setting 5
  • RAT deployed
  • Mayday that they lost power
this rules out flap up instead of gear up , selecting wrong autopilot setting, gear up causing electrical faults (as problems started earlier - using up all runway). Something must have happened on the runway (after v1?) that led to loss of electrics (and dual engine failure, maybe later?)
Define facts! Reported by an eyewitness, reported by Indian media? The ' mayday that they lost power.' is not a fact but invented by a journalist. The " aircraft used the whole runway" is not officially reported by the investigators but noted by an Indian newspaper. In the same article of today this newspaper wrote about the fake mayday call.

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sorvad
2025-06-15T09:56:00
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Post: 11902306
Originally Posted by amsm01
(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
Well I’m a triple driver so can’t be sure for the 78, but during the preflight we can programme thrust reduction either at and altitude or at flap 5 or 1. The company I’m with at the moment it’s an altitude, the one I was at before was usually at a flap setting. I’m not sure it’s got anything to do with this accident though. I guess you could enter 150ft instead of 1500ft in the FMC for the thrust reduction which would be alarming when it happened for sure but doesn’t explain the RAT or the gear observations….. unless someone did something like the memory items in response to what they perceived to be a double engine failure, but at that altitude, with no confirmation of any failure? I wouldn’t have thought so but never say never.

Last edited by sorvad; 15th Jun 2025 at 10:15 .

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Travis Anderson
2025-06-15T09:59:00
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Post: 11902310
Originally Posted by Someone Somewhere
The issue is what maintenance error could cause simultaneous dual engine failure, or other hypothesized causes? But would not result in an immediate alarm (e.g. missing FADEC alternator) on engine startup/high-thrust?"
That would require deep dive in the maintenance records of that bird, and it's ludicrous to think we'll be able to figure it out. To cause dual engine failure at "gear up" callout (everybody's nightmare, unrecoverable) - that needs to be either drastic, super weird, or malevolent. And that hole goes too deep for us to guess.

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
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Post: 11902404
Originally Posted by Someone Somewhere
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.
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?

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Captain Fishy
2025-06-15T12:00:00
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Post: 11902407
Originally Posted by DaveReidUK
A TCMA bug just doesn't bear thinking about, I really hope that doesn't turn out to be the case.
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.

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mechpowi
2025-06-15T12:38:00
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Post: 11902430
Originally Posted by Captain Fishy
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.
This is the best theory of TCMA activation so far, but it\x92s still very remote. In this theory there is no need for a TCMA anomaly, it needs only(!) two simultaneous engine anonalies (and sn improper crew action) that would trigger the TCMA as designed. If there are safeguards preventing this happening, they are not mentioned in this thread.

It also doesn\x92t explaine the ADS-B data showing acceleration after lift off.

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island_airphoto
2025-06-15T13:17:00
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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.

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Pelican
2025-06-15T13:21:00
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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.

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LTC8K6
2025-06-15T13:23:00
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Post: 11902467
Originally Posted by Pelican
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.
It's been mentioned a few times that the bang might be the RAT deploying. But who really knows?
galaxy flyer
2025-06-15T13:24:00
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Post: 11902470
Originally Posted by island_airphoto
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.
The FADECs are completely independent of the plane\x92s electrics IN THE EVENT of the aircraft electrical. There\x92s a Permanent Magnet Alternator to power it.
JG1
2025-06-15T13:30:00
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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
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Post: 11902477
Originally Posted by Pelican
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.
As an expert on human memory and cognition has pointed out above (and we all more or less know), what that survivor remembers or he thinks he remembers \x97 and what we think or are told he doesn't remember \x97 cannot be considered accurate or reliable. At all.

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Icarus2001
2025-06-15T13:42:00
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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.
No please read above.

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.

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Someone Somewhere
2025-06-15T13:43:00
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Post: 11902481
Originally Posted by Skyscraper1995
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?
This discussion happened after Jeju. I note that one of the video sources here is actually leaked (camera-pointed-at-screen) airport CCTV. Do not mistake airport CCTV not being publicly available for it not existing.

Originally Posted by SteinarN
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?
We'd need to know the impedance/available fault current of the generators. 50x would be unusually high in an industrial setting.

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.

Originally Posted by syseng68k
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.
Not designed to parallel, but you still need to switch each generator on/off buses and tie or separate buses.

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.

Originally Posted by LTC8K6
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.
The 787 flight controls remain almost entirely hydraulic except for stab trim and two spoiler pairs. The centre system is now electric- or RAT-only with no ADP backup. Left and Right systems are still driven by EDPs and will remain pressurised as long as there's fluid and the engines turn.

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.

Originally Posted by scifi
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.
Battery is essentially unused in normal operations other than to start the APU and keep the clocks running. It's there for emergencies (like after the engines fail). And yes, been discussed.

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EGPI10BR
2025-06-15T14:27:00
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Post: 11902507
Originally Posted by JG1
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.
BAW38 didn\x92t give an engine failure notification either. Neither engine produced the required power when demanded.

Misty.

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Screamliner
2025-06-15T15:11:00
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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

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OPENDOOR
2025-06-15T16:06:00
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Post: 11902592
Originally Posted by Pelican
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.
If you look at the airport video of AI 171 departing and run it at high speed backwards and forwards the aircraft follows a smooth but shallow parabolic flight path. This is consistent with a total engine shut down just after departure.

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