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

Long story short. Something or someone disrupted the fuel supply on both engines simultaneously around rotation time. In a way that a line check captain could not correct it in 10+ seconds remaining flight time. Occam razor at this stage would say, that both fire handles were activated. Hope that the investigation comes up with something different.

Imaginations are running wild for some people here. Major electrical fault that leads to double engine failure at v2? Really? If that were the case the 787 fleet would be grounded by now given the black box has almost certainly been examined.

I think it needs to be said again that pretty much anything can happen to the aircraft systems and the engines will carry on running - this is by design as they have independent FADEC and power supplies and at sea level fuel will get through without boost pumps. You could almost saw the wing off the fuselage and the engine would still produce thrust, TCMA notwithstanding.

We don\x92t know yet what actually triggered the RAT from the relatively short list but every item on it means there is a serious/critical failure(s). The flight path suggests that it was a double engine failure or shutdown (commanded or uncommanded) as anything else should have left the aeroplane in a poor state but able to climb away.

Almost all catastrophic accidents that are not deliberately initiated require multiple causes. It’s extremely unlikely that both engine condition switches or fire switches were accidentaly actuated during a routine rotation and initial climb. However it’s stil possible that the crew did actuate those switches (intentionally or unintentionally) in response to some anomaly experienced at that time. Thus it’s not impossible that electrical system malfunction was the first link in a sequence that led to removing the fuel supply to both engines. The most obvious one is that crew thought that they had dual engine failure due to lost of main electrical power and initiated a double engine restart bycling the engine condition levers.

The purpose of this post is not to promote the above as a possible cause of the accident, but to remaind people that a (proven) mechanical fault does not rule out pilot error and vice versa.

Agreed. These possibilities are so infinitely small that it seems folks are dwelling on minutia. Interesting minutia but of such low probability.

We`ll just have to wait a bit until some facts come out.

Not ready to shelve the flap/RTOW probability quite yet.

Or even deliberate (or inadvertent) actuation of the FCSs. Incapication, etc.

The Mayday specified loss of control and engine failure.

How about the other way around? Double engine failure stops most of the electrical power?

The 787 is far more heavily dependent on electrical power than previous Boeing designs.

Dont follow that logic at all\x85 this flare in the last second or three wasn\x92t IMHO to stretch the glide but reduce vertical impact speed.
sully flared almost perfectly, nothing to do with \x91stretching\x92 the glide.

Several hundred posts ago, a link to a PPrune thread re 787 RAT deployment was posted. I am sure everyone posting has at least seen if they have read the thread....

I apologise, if my thoughts have already been posted - please delete if this is the case, I cannot find them in the main thread though

None of us know if there was no engine failure, single engine failure or double engine failure.

If RAT was deployed, we do not yet know whether it was automatic or manually deployed by a very experienced captain because "We have no power. What harm can it do now?" (Electrical power, not thrust) Would the Captain also elect to start the APU in the few seconds he had?

In the thread re 787 RAT deployment, some one states that a single engine failure, due to the small rudder size on 787-8, automatically throttles back the remaining engine as the rudder will not be able to correct the course. I am not clear about the guards around this - be they height restrictions, speed restrictions or % of power delivery. If there are any guards in the software. It may have been stated and I missed it or didn't understand.

However, as someone involved with critical software design & development, if the generators were "playing up", which is highly possible given passenger observations on previous flights, could there be a window, if the aircraft experienced a problem with say no 1 engine ( suggested in video "analysis" despite the aircraft tracking right ) whereby the loss of electrical power triggered the software to "throttle back" No 2, and that again limiting any recovery of No 1, if the generators on 2 didn't perform/react as planned. Software always has holes.

The primary flight deck screens have battery backup - but do they lose power when the main buses go offline - and/or again when the RAT delivers? Or is it seemless? Previous posts mention both scenarios but with no answer. Are there flickers, resets, reboots? All distracting at best and time limiting at worst.

I think a pertinent point posted earlier, was that the problems seems to have begun with "gear up", a lot of load on the electrically driven, hydraulic pumps.
Seemingly started, but obviously not completed.

I believe the 2 guys sitting in row 0 dealing with this, were just passengers from the moment it left the gate - for whatever reason. The mayday call, by whichever pilot - although no transcript officially published - was probably a last ditch attempt to alert ATC asap to a situation with a clear outcome. Very sad. It is bad form to point the finger before any useful facts are confirmed.

So, I suspect generator problems & a hole in the software and/or logic due to timing issues caused by generators appearing to be on/offline -maybe rapidly - restricting thrust by design..

Yes, thanks, I've seen a few comments to this effect, and I have to accept most of what you say. I understand that they have their own dedicated generators and local independent FADECs (or EECs), but I'm trying to use what I do know to attempt to figure this out. I know that there are Fuel Cutoff switches in the cockpit. Somehow, if switched to Off, these will cut off the fuel to the engines, "no matter what". Of course, even that's not true, as the Qantas A380 engine burst apparently (comment in this thread) showed.

Anyway, the thing I'm looking at is how the fuel cutoff switch function could have been activated in some other way. To me, it seems obvious that there are wires that run between the engine fuel shutoff valves and the cockpit / flight control panel (no doubt with relays etc in between). I don't know where those shutoff valves are located, but logic says they should be located in the fuselage, not out at the engines. I also don't know how those valves operate - are they solenoid valves or electro-mechanically driven? Nor do I know where the power to activate those valves comes from, but using my logic, if those valves close when powered off, such as solenoid valves typically do, then the power cannot exclusively come from the engine-dedicated generators. If it did, you'd never be able to start the engines so they could supply their own power to hold those valves open. So, there must be some power (appropriately) fed from the main aircraft control bus to activate those valves - if the rest of what I'm assuming is correct. Anyway, like I say, I don't know enough about the details at this point, but there are many more ways to activate or deactivate a circuit than by flicking a switch. Killing the relevant power supply, for example. A screwdriver across some contacts (for example), another. Shorting a wire to Chassis, maybe. Just trying to contribute what I can.

You raise another interesting point: "TCMA notwithstanding". Could you elaborate, please? What will happen if the TCMA system, which apparently also has some degree of engine control, loses power? The problem with interlinked circuits and systems is that sometimes, unexpected things can happen when events that were not considered actually happen. If one module, reporting to another, loses power or fails, sometimes it can "tell" the surviving module something that isn't true... My concern is where does the power to the Fuel Cutoff switches come from? Are there relays or solid-state switches (or what?) between the Panel Switches and the valves? If so, is the valve power derived from a different source, and if so, where? Are the valves solenoids, open when power applied, or something else? What is the logic involved, between switch and valve?

Would you mind answering these questions so I can ponder it all further, please? If I'm wrong, I'll happily say so.

100%

I assume the dual engine shutdown due to engine overspeed. Could the case occur with increased thrust manually in the end of takeoff phase?

Do not discount the mistaken early flap retraction scenario too easily. Mull on this:

PF commanded gear up on attaining positive rate of climb, fixating on the HUD.
PM mistakenly raise flap lever from 5 to Flap 1 gate. Thrust reduced to Climb Thrust. Landing gear remained deployed. Massive loss of lift misidentified as loss of thrust. If any one pilot just had a dual engine failure scenario on a recent sim ride, brain and muscle memory would jump to loss of thrust in dual engine, prompting them to accomplish the recall memory items which called for both engine fuel control switches to CUTOFF and then RUN, and physically deployed the RAT.

There would be immediate loss of thrust with the engine taking time to recover , if at all, at such low airspeed!
The rest is left for Ppruners’ imagination.😖🥴😬

I keep reading this theory and I'm baffled. You think the PF is going to attempt a dual engine shutoff and relight during the initial climb based on a hunch that the engines have quit, all without even a sideways glance to see what N1 is or a short word with the PM?

I don't want to believe it either. It defies belief but given certain confirmation bias (sim), panic and inexperience by the FO, it's not beyond the realms of possibility. It explains both the RAT and loss of lift. The alternative right now is a catastrophic electrical failure that wiped out the engines or engine control leading to loss of thrust, or a dual engine failure due to birds, fuel contamination or FOD. They are also valid, though IMO less likely.

If the photo of the flaps deployed at the accident site is actually F1 not F5 or if the flaps were pushed out during impact, then this is certainly plausible. I will look for the photo but it's in the thread somewhere. Others are stating they see a gap between the wing and the flap as an argument for the flaps deployed at F5. This was after the decent started..

However, I think their reaction would likely be to apply more power. I know mine would be. But anything is possible!

Brilliant, now what is your point? Are you suggesting a double engine failure, a roll back to idle thrust or an incorrectly set AAI causing VNAV level off and a thrust reduction. You can only choose one.

For the team pointing to the RAT out as a failure indicator, it could have been deployed by the crew after the initial reduction in climb performance. I am not convinced it is deployed but it really does not make a convincing argument for any type of failure.

For the children on holiday, yes I fly transport category jets, current on two types.
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Yes indeed. I strongly leant toward the incorrectly set AAI and VNAV capture and level off as the a/c reportedly reached max alt of 625ft or about 450ft AGL. Even with startle factor, recovery should have been quite possible. The video I have seen (not the video of the video) clearly shows the RAT deployed and you can hear the whine of the turbine and virtually no engine noise . This complicates it for me as there is no logical reason to deploy the RAT in the VNAV/level off scenario.

In reply to you, I am solely stating that it's a thrust-side problem. I think I somewhat misinterpreted your post as it looks like you might have been saying that anyway.

In general, I think it's looking like dual engine failure/shutdown cutting electrics. I agree that why it occurred is very unclear. Outside chance of total electrical failure causing dual engine failure rather than the other way around, but that would perhaps be even more concerning a design failure.

Similar to Jeju, we also have what is looking increasingly like a loss of ADS-B data at the moment things went wrong, not just a loss of coverage.

That gives:

• Sound of RAT
• Visible RAT
• (edit: APU door open implies APU autostart)
• Loss of ADS-B out
• Near-total loss of thrust.

The alternate theories seem to be a) flaps (basically discounted), b) suction feed failed after total electrical failure, or c):

• A/T rolled engines back
• Crew interpreted this as dual engine failure
• Crew didn't push throttles forward
• Crew did switch each engine off & on again and maybe deployed RAT manually as well.

I think it has been suggested that the upload only happens every 30 minutes or so.

This is a very plausible scenario. Above 400 ‘ AGL, memory items.

(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\x92t 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