Posts about: "Engine Failure (All)" [Posts: 410 Pages: 21]

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.

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?)

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?

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.

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.

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.

This has been reported but not naming any verified or even specified source. I have also recently read in this thread at least 2 different versions, the most recent one before yours, upthread, being even more specific than the one that went around at first. Despite what is being quoted by yourself and others, with no verified source, the Indian Aviation minister reported at the most recent press conference that the mayday message was as follows :- "mayday, mayday". ATC replied asking for further info, but got no reply. Despite a lot of searching online, that is ALL that is currently verified, so far, re the mayday call.

I cannot get my head around any of the likely scenarios as there seems to be a lot to go wrong to get to the end result. One of the things that has confused is that it looks like they go off the end of the runway. ie no more runway left and the look of soil being blown up into the air.

I kept looking at that video where it disappears behind the shed and I could be seeing things but as it rotates it "looks" like it starts to yaw left and change direction. I have spent a fair few years as a TRE and I have seen plenty of times in the sim where insufficient rudder after an engine failure will lead to a slightly undignified slide over the side of the runway after they get airborne. I wonder if that dust is actually from the side of the runway rather than the argued end of the runway. I temper that thought with the fact of the change of zoom might create that illusion.

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?

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.

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.

Indeed.

Aviate: The aeroplane has decided it doesn\x92t want to do that any more.
Navigate: Not many options on where to go.
Communicate: May as well let people know it\x92s going to be a bad day and to get there ASAP.

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.

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.

It's been mentioned a few times that the bang might be the RAT deploying. But who really knows?

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.

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.

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.

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.

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.

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.

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.

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.

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.