Posts about: "Electrical Failure" [Posts: 111 Pages: 6]

TE Flaps are extended, flap gaps between the wing and the flap element are observable. This is not an aberration of the spoiler position, you can see the nacelles through the gap, and that means the flap can not be in the retracted position.

An error of the TE flap deployed position, say between flaps 5 or 15 is not going to cause a stall event.

The flap has not been retracted instead of the gear.

Double engine failure... India. birds, always a latent threat. No rudder deflection, no aileron deflection, so it's not a SE problem, any engine issue is affecting both engines.

Pitch control and roll is not compromised in the video. The crew put out a mayday, not sounding like an electrical fault or distraction.

any funerals near by?

Incorrect TO thrust setting would not present in the video as recorded. Low thrust results in low acceleration, and extended distance to rotate. after rotate, low thrust results in low climb rate, and can result in the crew over pitching where the aircraft has obstructions that the crew have to avoid. the video appears to show the pitch increasing at a point where the aircraft is already unable to climb, not the other way round. An outside possibility.

For survivors, any from the aircraft will be a miracle, and mainly from the rear of the plane near door 3 area, if any. Plane is still striking tank traps at 70m/sec +, high ANU, it's not a high survivability event. Occupants in the buildings along the flight path will have a high fatality rate as well. This is going to be a high toll event in the aircraft and on the ground. Bad day at VAAH. RIP.

What are the electrical systems like on the 787? I only ask as there is a very early post where a guy flew the aircraft on the way in and at least in the passenger cabin, it was electrical gremlins galore.

most of the aircraft IFE screens unpowered, call bells not working, no AC, nothing.

What if they were already flying with one of the systems in-op? Aircraft hot on the ground (air temp was 42c) if i recall)

how does the wiring of a 787 and its electrical sources work and is there any potential for it to interfere with A/T if there was an electrical failure, adding in the fact that the 787 is running on lithium packs.

The only thing that would rule out complete electrical failure would be the mayday call - but for those knowledgeable, is there any electrical event that could cause this?

at the risk of sounding daft, its almost as though everything just went off, at 200ft.

This aircraft has got airborne well within the requirements of FAR 25 under which it was certified. It has over 1250m ahead of it passing around 35' based on the video from behind, so the FMC data was not incorrect, the thrust up until after TO was not incorrect, and the CG is not out of range, the time to rotate is within expected range, and the attitude at liftoff is not excessive, the plane is not heavier than expected. This is not Emirates, Tiger or SQ, it may have a resemblance to AFR out of Nigeria, or ANZ out of Raro, or UAL out of Hilo. Unlikely but there are similarities.

A low altitude in the MCP can become pretty interesting, as will a TAT probe failure to the ATR thrust limit. Both cases will have the thrust levers moving back rapidly. There is no obvious failure of the engines at this point save the question that the RAT may be deployed. A transient electrical fault tripping the logic for the RAT is hard to imagine, but that would possibly end up with an ATR fault and power coming back to idle. Fuel contamination is not impossible, but it is improbable, the engines would have been on their TO configuration from the engine start, and the taxi and turnaround takes enough time to flush the fuel lines, being longer than the selected tank sampling time that sits behind the SOPs. Boeing aircraft are easier for the crew to detect anomalous thrust commands compared to the Airbus, however, if the RAT is out... then more was happening.

The flaps are in the correct position, we are looking at a time critical failure for the crew, they appear to have around 10 seconds between onset and impact, and they have rotated the aircraft in the later stages, as any reasonable pilot would do, and that certainly does not indicate a crew initiated problem on the available information. Unlawful interference is unlikely, given the RT calls that have been made.

The IDGA AAIB is not known for rapid response, this event is of international importance, it appears that it is being treated as such by the authorities involved. The EAFRs on the 787 will tell all soon, and we need that information, this is a globally important aircraft type.



The pilot is being quoted as saying to ATC:

"Mayday...no thrust, losing power, unable to lift"

I don't think a pilot with over 8000 hours experience would mistakenly diagnose that. Also corroborates with the RAT being deployed. Question is how do both engines lose thrust. Bird strike is the obvious one. Fuel contamination seems unlikely.

I see a post above showing how its possible an electrical failure can result in power loss. Passengers on the flight before this said there were issues in the cabin; lights, displays and air con was not working. Again, seems v unlikely to be related.

That post is simply wrong - if all aircraft electrical power is lost, the engines will keep running just fine (suction feed is demonstrated to be sufficient in the entire takeoff envelope, so even losing boost pumps wouldn't cut engine power).

This seems to be the best summary so far. Based on the detail of the mayday its probably time to rule out the flaps, load shift, and other suggestions. Latest news is a quote from the survivor: " Suddenly, the lights started flickering – green and white – then the plane rammed into some establishment that was there" .

I cant think of any reason for electrical failure and "no thrust" (as per statements) without any visual cues other than (a) suicide, or (b) starvation. Is there any electrical failure that can cause fuel valves to close? I dont fly Boeing, so can any Dreamliner driver explain what conditions could trigger an overspeed and auto engine shutdown (quote from Google below)? Would short runway, and hot/low QNH do it? Also, what happened to the order demanding a full power down/recycle every 51 days?

The EEC has build in protections to protect the engine. One of these protections is the Engine Overspeed Protection, when the core engine exceeds 120% the EEC shuts off the fuel to the applicable engine.

SLF. I don\x92t know how B787 systems work but if that\x92s correct it must be a possibility. It seems as though engines are working fine until airborne. I\x92d just been asking elsewhere if it were possible that an electrical fault with the software could prevent both engines running? I know they don\x92t require outside power to continue to run, but if software was disrupted by a catastrophic electrical fault (issues reported on previous flight supposedly) would they shut down? But an error in the software could be more likely than the sort of failure requiring multiple backups to also fail I guess, and would also explain the timing of the engines shutting down/throttling back.

RIP to all the victims.

This is a quote from the sole survivor so don't shoot the messenger: "When the flight took off, within five to 10 seconds it felt like it was stuck in the air. Suddenly, the lights started flickering – green and white – then the plane rammed into some establishment that was there".

This might indicate evidence of a possible major electrical issue which could have disabled critical aircraft systems.

I've just watched the interview on Sky News. I too picked up on the green and white light coming on. He is sat at an exit so the green and white light is most likely the emergency exit sign illuminating. But on take off? They usually illuminate on electrical power loss.

He also states, 'soon after take off . . . maybe 5 to 10 seconds, and it felt like the plane was struck, it felt like something had happened . . . the pilot was trying to give it a bit of a push, but it was struggling . . .'

Not sure what the witness means by pilot trying to give it a bit of a push, does he perhaps mean he heard the engines getting louder.

We of course understand witness reliability, particularly with trauma, but he is the only human witness present in the aircraft that is able to speak.

Many GE engines - including GEnx-1B/67s - require microprocessors to be routinely replaced due to soldered joints failing after multiple cycles. There is a 2021 AD that notes "This AD was prompted by an in-service occurrence of loss of engine thrust control resulting in uncommanded high thrust" (I cannot post a link but google: 2021-25491 (86 FR 66447))

I am NOT suggesting that this specific failure mode happened here - for one thing, this would happen to one engine, not both. But on any flight it is possible that a unique set of sensor inputs to occur that are the first time any system has encountered them (example: NATS incident in 2023), and then you need failover & redundancy to keep things working.

The GE Aviation CCS system, which includes thrust management, has up to now flown for 1m flight hours without incident. It would be interesting to hear the perspectives of any engineers familiar with the system.

Reading the various reports about electrical problems on the prior and this flight, such as flickering lights reminded me of the BMI A321 incident discussed here 15 years ago:

https://www.pprune.org/archive/index.php/t-433616.html

A faulty generator caused all sorts of problems with control of the aircraft. It is a reminder that complete electrical failure is not the only failure mode. Shutting down the faulty generator on that aircraft recovered the situation, but they had time and altitude on their side.

Assumptions
30 secs to 100 kts from TO power set.and 200 kts after 60 seconds
Impact occurred 30 secs after Vr 1 nm out, so about 120 kts and no more than 300ft
The gear was not or could not be retracted.
Without doubt the crew knew impact was inevitable at least 10 seconds prior to impact noted by body angle change in video evidence
whether a Mayday Call was in fact made or not.

I think that the only thing that would matter for any of us in that 20 seconds would be THRUST and everything it's got.
Which occurred first, the loss of thrust on both engines causing all generators to go offline or a total electrical failure that caused flight Idle thrust.

Two pieces of information have emerged in the last 24 hours which are, I think, indicative of where this will end up.

1. Pilot Comms reporting total loss of thrust
2. Survivor report of flickering green and white light

The first supports (and is supported by) the lack of apparent engine noise in the available videos

The second indicates an INTERMITTENT electrical fault of significant systems (emergency lighting being responsive to aircraft wide power issues and guarded in a way that IFE might not be)

[Speculation] Intermittent failure and transient loss/spike of current could overwhelm soft and hard controls against inappropriate engine cutout

Ive seen it happen in a previous (ground based) life fairly frequently (in relative terms) but exclusively during descent/approach. Usually the context would be expecting a flap call but when the gear call is made the flap handle is moved and quickly returned to the previous gated position followed immediately by gear selection, confirmed upon review of the data. To happen on takeoff would be most unusual, and although the CCTV footage is indicative of it being highly plausible, neither pieces of footage really show anything to draw any conclusions on. Certainly there may be numerous aspects to this, perhaps there was some catastrophic electrical failure that wasn\x92t of itself an immediate threat to the flight but the startle effect in the flight deck prompted other reactions. It\x92s impossible to know based off the information available. The human element will form a significant part of the investigation regardless of root cause(s).

Regarding the comments about who should be allowed to comment on such threads. I like the fact the mods have taken a pragmatic view of this. Theres a reason many in the accident investigation field come from an engineering background. Whilst highly experienced pilots are clearly crucial on an SME level, there can be a tendency for iwouldnthavedoneitthatway-itis. This can at times hinder investigations where an open mind free from confirmation bias is essential.

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.

An early number 787 (in the first twenty four), had to make an emergency landing at New Orleans on a Houston to Newark flight. At this point, re Air India, with the RAT screaming in the original video, an electrical issue of some magnitude is at the fore. Each engine has two generated power unit (GPU). Total of four (NOT ground power unit). If one of these goes offline, the system adjusts. If an engine quits, two are gone, and the remaining two supply e power.
Powering up all four at once can cause a shutdown of all generated power. The question becomes which failed first, the engines or the electrics. The RAT deployment signals either both engines shutting down, or four GPUs. I think negative on Pilot Error.

Whatever the direct cause, this amount of grief is impossible to imagine. God have mercy

In summary,

Flaps were extended, possibly flaps 5 or 15. Looks like it in the video and clearly shown post crash.

Aircraft reached a height of just over 100\x92 AGL (possibly 200\x92 if you compare wingspan to height in videos)

RAT was deployed. Seen on videos and heard conclusively.

Aircraft rotated at \x91usual\x92 spot. Comparing FR24 data from previous flights over the past week.

Aircraft took off at \x91usual\x92 speed. Comparing other flights.

FR24 data stopped being sent shortly after take off. Possibly indicating electrical fault.

Green and white flashing light reported by survivor. Possibly indicating electrical fault.

Gear bogies were at unusual angle indicating Gear selected up and then interrupted.

No smoke or flames to indicate bird strike. (Edit - still debate about this in the video above where the aircraft is behind a building)

No rudder input to indicate single engine failure.


All speculation but hopefully a pretty balanced summary from the thread so far. It would be great if there was more focus now on what might have caused above rather than talking flaps, birds, 625\x92, etc.

I agree it is helpful to seek a consensus on some of these matters.

The most productive responses would be along the lines of:-
(1) I too have read all previous posts and agree that your summary reflects the current consensus,
(2) I too have read all previous posts and agree your summary reflects the consensus HOWEVER I challenge that consensus because... [ [i]EITHER (a) reference to previous post that merits greater credence, OR (b) new evidence supplied],
(3) I too have read all previous posts but I do NOT agree your summary reflects the consensus [explanation required].

It is not necessary for everyone who thinks (1) to say it (although some initial feedback would be useful!). However, if any of the more experienced and informed PPRuNers are thinking either (2) or (3) then it would be instructive to hear that.

FWIW, yours strikes me as a reasonable summary of the best consensus I have been able to discern (as of ~30 minutes ago). There are multiple caveats to each line item, but I presume you've deliberately left those out for the sake of readability, so I'll do the same!

The only comments I would add are:-

- It's a stretch to say the RAT is seen or heard "conclusively". Doubts have been expressed about the video quality and there are dissenting views regarding the audio. If a few more people were able to wade in on the audio point in particular, this could be very beneficial in moving the discussion forward because the presence or otherwise of the RAT is significant to several competing theories.

- On the subject of audio, I am surprised there has not been more discussion regarding engine noise. In the primary eye witness video the (alleged) RAT can be heard distinctly, as can the sounds of distant impact. If the engines were working as expected when overflying the camera and then flying directly away from it, do we really not think the engine noise would be more conclusive, i.e. louder (notwithstanding quiet engines and derated takeoffs)?

Whichever way readers are leaning in the flaps versus power loss debate, surely these two points are pivotal, and we have actual evidence available to discuss?

- Gear bogies: I'm not sure a consensus has yet been reached regarding the angle of the bogies. (I am not personally qualified to comment on this - I am purely saying I don't see a clear consensus just yet among those who are)

- Mayday call: I don't recall seeing a confirmed source for the widely reported mayday. Others have brought this up in the thread but nobody appears to be able to confirm one way or the other. If accurate, its contents are informative. Am I right to presume that you have left it out of your summary due to a lack of confirmation?

This crash reminds me of the crash of a 747 Military Transport plane at an airbase in Afghanistan.

Shortly after TO, the cargo shifted, the plane became very tail heavy and stalled a few hundred feet in the air. It was the weirdest sight. For what seems a few seconds, the plane just seemed to hang there, presumably on engine thrust.

In this crash, the problem also seems to occur soon after rotation, as if something inside moved in response to its change in attitude. Maybe a loose connection on a main bus cable that moved... Maybe only a millimetre. Or a tool left inside an electrical cabinet slid somewhere it shouldn't. The possibilities are numerous, and without a lot more information, there's no way to know what caused this. I suspect a major electrical fault, probably intermittent.

How long would it take to restart those engines after a Fuel Cutoff flame out? Is that what happened, just before impact?

I did read and search this thread, but I found nothing about ADS-B loss just before the end of the runway and at 71 ft high, according to FR24. ADS-B coverage is poor on the ground on the north-east part of the airfield (hence the fake news about taking off from the intersection) but I don't think it would be lost once airborne, except if it has been shut off... electrical failure ?

more precisely, loss of the two Main AC buses (ADS-B not powered by Standby AC)