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

Gupeg
2025-06-15T16:46:00
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Post: 11902623
Originally Posted by NOC40
Flightradar24 (I know, I know) has a short blog on the (very minimal) ADS-B data available. There's only around 4s of useful data available from 21ft o 71ft altitude (last packet received 0.8s later), But: it's odd seeing the speed DROPPING shortly after takeoff. Even if you calculate total energy (kinetic + potential) it's falling, i.e. the engines aren't producing thrust. (In fairness reported speed doesn't match my calculated speeds, but even with mine I don't see power). Also: if you assumed no thrust from 71ft AGL @ 172kt you'd reach 250ft at 160kt. Isn't that roughly where they ended up? Noisy data, but this suggests the engines stopped producing power almost as soon as the wheels left the ground. (If someone could download a CSV of another similar flight and send to me I can do a compare and contrast of Total Energy)
If you wanted to an analyse this further:
1. You might mathematically start at TE=0 at start of takeoff-roll, and treat drag as minimal until rotation.
2. Typically rotation will be to say 15deg nose up, but flight path will be much less (5deg? for heavy hot 787). Once that rotation is complete, aircraft will stop accelerating. Therefore engine thrust (energy gain) equals gain in PE - drag x time.
3. This might give a better insight into where energy gain/loss became unusual?

Looking at the raw data in your post, and given the speeds are likely IAS based i.e. can be affected by wind, I don't see the IAS loss as equating to dual engine failure i.e. zero thrust - but could be wrong. Once a heavy airliner gets to lift off the acceleration is reduced (drag) and the decays to zero as PE gain kicks in.

Ditto a time / distance to the crash site might give some energy info? Looks like the crash site is 50' (?) below the airfield (Google Earth will give more).

I think you are doing an interesting study on the absence of other info
Engineless
2025-06-15T17:15:00
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Post: 11902643
Originally Posted by FullWings
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 .
Firstly, I've read through this whole thread - thank you Admin & Mods for your considerable efforts to clean things up.

Secondly, as a (now ex) glider pilot who remains extremely interested in aviation in most of its forms, this discussion has been an education and thought-provoking, as it so frequently is whenever I lurk here (usually without logging in). Thank you all for sharing your knowledge, expertise and thoughts.

To my mind the above post (especially the sentence I highlighted) is amongst the best (and most succinct) summary of what the pilots likely faced, with little to no time to resolve the situation. I cannot imagine those last few seconds and my heart goes out to them, the passengers and the many loved ones left behind. If there is any good that can come of this, it is that the cause is found quickly, with no bias, and steps are taken to ensure the same holes in the cheese cannot happen again.

7 users liked this post.

adfad
2025-06-15T17:16:00
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Post: 11902645
Originally Posted by Screamliner
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.
How long does it take for an engine to fail in terms of thrust output - what does thrust over time look like for various failure scenarios - e.g., no electrically powered fuel pumps, or contaminated fuel, or thrust set to idle or other issues?

The original mobile video (not the copy from someones phone screen) clearly sounds like a RAT but what does the engine itself sound like - is it idle or reduced in some way?

What is the minimum amount of thrust that would need to be lost to stop climbing and sink back down - it took 30 seconds from leaving the ground to impact from the CCTV and the first 15 was climbing.

I would look carefully at the fact that the PCU still has the technical ability to tell all AC generator control units to turn off via software, as proven in the documented and fixed 248-day software issue.

1 user liked this post.

StuntPilot
2025-06-15T18:15:00
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Post: 11902683
Originally Posted by sorvad
Visual evidence the rat was deployed, audio evidence the rat was deployed, evidence the APU inlet door was open, evidence the gear retraction was interrupted, evidence there was very little engine noise after departure, very obvious evidence that the aeroplane didn\x92t have enough thrust to stop it descending into the ground. All of this strongly suggests that both engines were to all intents and purposes, and for want of a better word, \x91failed\x92 now that could be intentional, accidental or because of some sort of technical malfunction or external factor. Nothing conclusive and no answers as to how or why, but not quite as wildly stabbing in the dark as your post would infer.
We agree that there was a lack of thrust. Possibly caused by a dual engine failure. But the sharpest frames in the video do NOT show the RAT and this is counter evidence to the RAT theory. If there were substantial technical failures who knows what sounds could be generated. I find the evidence weak at best. And we immediately get into a chicken-egg problem: did some power issue of unknown nature cause an engine failure or did a dual engine failure occur, resulting in a power loss? Both are extremely unlikely and need to be backed by quality evidence. The video is not it, in my opinion. I don't know the APU intake mechanism and whether it could open after the impact.

2 users liked this post.

njc
2025-06-15T19:03:00
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Post: 11902726
Originally Posted by tdracer
The 'good' news is that even a cursory check of the FDR will indicate if TCMA activated, so we'll soon know.
The investigators will certainly soon know, but how sure are you that they'll share that in public?

Originally Posted by Screamliner
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
Nope, you may not have read the whole thread - the full set of conditions which can trigger the RAT have been posted multiple times before your reply

Originally Posted by Stivo
Am I understanding that you are saying that the noise on the video identified as a RAT has a Doppler shift that matches plausible values for height and speed? That seems pretty conclusive to me that it is a RAT.
I'd phrase it differently: the frequency (and harmonics) of the noise are consistent with it being a RAT. If you then assume that it was a RAT and infer distance and speed curves from the Doppler variation, you get plausible values for an aircraft. But the two things are somewhat linked so you can't really treat the second thing as confirmation of the first. (FWIW, I'm personally quite satisfied that it was indeed a RAT on the audio.)

4 users liked this post.

sorvad
2025-06-15T19:15:00
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Post: 11902740
Originally Posted by StuntPilot
We agree that there was a lack of thrust. Possibly caused by a dual engine failure. But the sharpest frames in the video do NOT show the RAT and this is counter evidence to the RAT theory. If there were substantial technical failures who knows what sounds could be generated. I find the evidence weak at best. And we immediately get into a chicken-egg problem: did some power issue of unknown nature cause an engine failure or did a dual engine failure occur, resulting in a power loss? Both are extremely unlikely and need to be backed by quality evidence. The video is not it, in my opinion. I don't know the APU intake mechanism and whether it could open after the impact.


Alty7x7
2025-06-15T20:23:00
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Post: 11902791
Engine failure with electrical power loss

Originally Posted by StuntPilot
We agree that there was a lack of thrust. Possibly caused by a dual engine failure. But the sharpest frames in the video do NOT show the RAT and this is counter evidence to the RAT theory. If there were substantial technical failures who knows what sounds could be generated. I find the evidence weak at best. And we immediately get into a chicken-egg problem: did some power issue of unknown nature cause an engine failure or did a dual engine failure occur, resulting in a power loss? Both are extremely unlikely and need to be backed by quality evidence. The video is not it, in my opinion. I don't know the APU intake mechanism and whether it could open after the impact.
To simplify the chicken/egg:

Tdracer earlier confirmed that an airplane electrical power loss would allow engines to keep running , because 1) engines are fully-capable of suction feed operation in takeoff envelope (if boost pumps lost), and 2) the EECs are powered by their own PMAs when running and to substantially below idle (I recall roughly 10% N2). Airplane powers the EEC for ground starts, prior to PMA coming online, and as backup to the PMA after that.

Related:

Engine igniters are powered by the aircraft. So theoretical full loss of aircraft power would disable Autorelight upon a flameout. Ignitors typically don't make the cut for most-essential battery-only loads because it would also take an engine flameout, and the airplane past V1 in ground roll can fly fine on one engine that can achieve takeoff thrust.

Autorelight is relevant - if there was a single-engine failure post V1, autorelight will attempt to relight the engine, so there is no need for a pilot to try to cycle the fuel switch to reset the EEC (potentially grabbing the wrong one), or to otherwise intervene. In such a circumstance, they need to trust their training. I've heard accounts that the most likely pilot instinct in such a situation would be to push the throttle(s) forward.

Finally - there was talk earlier about accidentally cutting the fuel switches - and it was duly noted that they have to be pulled out over the detent, so very unlikely. The same cutoff effect could be achieved with the engine fire handle(s), right behind the fuel switches on the pedestal - though they are an upward pull, so also not subject to inadvertent or accidental engagement.
Captain Fishy
2025-06-15T21:56:00
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Post: 11902882
Originally Posted by bakutteh
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\x92 imagination.😖🥴😬

A loss of lift AND thrust at this critical juncture could have had caused this awful disaster. I think the data recorders have already revealed the cause but If it's this, then I don't think we will hear much anytime soon.
OldnGrounded
2025-06-15T23:55:00
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Post: 11902983
Originally Posted by DIBO
but that was on the 747-8
Ah, yes. Missed that. Thanks. But I have to assume (I know) that any responsible aviation engineers designing a system that can shut down both (all) engines simultaneously when the airplane is on the ground is going to want to make very sure that the airplane is on the ground.

But I'll check.
bakutteh
2025-06-16T06:41:00
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Post: 11903143
Fuel Cavitation/Vapour block?

If decrease in thrust not by transition to climb thrust due to early inadvertent flap retraction and pilot action on fuel control switches from accomplishing dual engine failure memory items, then fuel cavitation /fuel fumes lock may be a cause. Just saying.

1 user liked this post.

Europa01
2025-06-16T08:03:00
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Post: 11903225
TCMA / FADEC

Originally Posted by tdracer
Repeating myself (again), but ALL the TCMA logic is resident in the FADEC. It takes aircraft inputs of air/ground (again, not familiar with the specifics of the air/ground logic used on the 787/GEnx-1B, so don't ask), thrust lever position, and what the engine is actually doing (mainly N1) to determine if the engine is 'out of control'.
The thrust lever inputs are hardwired (resolvers connected to the thrust levers, powered by the FADEC), other aircraft communications on the 787 are on an ethernet based network. Default mode for the FADEC if aircraft inputs are lost or invalid is "Air", as that is generally considered to be the 'safe' choice.
But even assuming some aircraft fault caused the FADECs to falsely believe the aircraft was 'on-ground', it would still take a pretty major error in the TCMA logic for it to actually trigger and shutdown the engine (especially lacking an associated thrust lever movement to idle). Never say never, but we're getting pretty far out on the probability tree for all these things to happen.
Yes. Thank you tdracer. All those postulating TCMA / FADEC faults please read and understand this clear explanation.

Then, ask yourselves which extraordinarily low probability bundle of previously unrevealed faults could spontaneously manifest themselves on both engines simultaneously.

Also ask yourselves why these faults manifested at that critical phase of flight and not during taxiing or take-off roll when some of the TCMA sensors would have been primed.

2 users liked this post.

unworry
2025-06-16T08:15:00
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Post: 11903233
Originally Posted by Europa01
Yes. Thank you tdracer. All those postulating TCMA / FADEC faults please read and understand this clear explanation.

Then, ask yourselves which extraordinarily low probability bundle of previously unrevealed faults could spontaneously manifest themselves on both engines simultaneously.

Also ask yourselves why these faults manifested at that critical phase of flight and not during taxiing or take-off roll when some of the TCMA sensors would have been primed.
After reading tdracers informative post this morning, I too was musing: Why is all this attention being given to TCMA.

Of course, when the probable cause is profoundly unclear, our continuing distrust of latent technical systems comes to the fore .... as sadly, the shadow of MCAS still looms large in our imaginations

Last edited by unworry; 16th Jun 2025 at 08:26 . Reason: a word

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yngve
2025-06-16T08:30:00
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Post: 11903248
Having followed this thread since the beginning, it is clear to me that this discussion is tainted by the fact that many contributors have MCAS and Boeing quality issues at the front of their minds.

I perfectly understand that, so no judgement from me, but it no doubt causes confirmation bias with conclusions being made about extremely improbable outcomes (dual engine failure at the same time during rotation/take off).

The RAT being deployed does not prove a TCMA-failure on both engines nor does it prove that both engines failed (its still not disproved or proven if it was manually deployed).

1 user liked this post.

Compton3fox
2025-06-16T09:21:00
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Post: 11903303
Originally Posted by 172_driver
I have not read it all so pardon me if this has been covered already. The A350 had two separate cases of engines shutting down due to spilled coffee on the center console. It was just a thought that occurred to me, a forgotten water bottle left on the center console during rotation? Pilots are usually quite conscious about the liquid free areas but this happens at home, in the office... If someone with insight care to explain how the electrics is protected I am listening...
It was posted but in a nutshell:

Airbus assumed their pilots would not spill their drinks but they did, and this resulted in an un-commanded dual engine shutdown. Now they have to use Sippy Cups!

Boeing assumed their pilots would spill their drinks so made the system robust enough to tolerate liquid spills without shutting down the engines.

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Icarus2001
2025-06-16T09:28:00
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Post: 11903310
Therefore I expect the recorder/s will only be read today or tomorrow. So "if there was a major issue they would know by now" is unlikely
My information differs to yours, We do know the EAFR was recovered on Saturday. Are you suggesting that it sat in a room for three days?

​​​​​​​ Dual engine failure is very unlikely to occur but this seems increasingly to be the case here. Possibly there was a single engine failure followed by shutting down the remaining engine by mistake, if this happened it wouldn't be the first time.
Wow you seriously think a professional crew would shutdown an engine below 400 feet?
​​​​​​​Is there any yaw or rudder deflection in any videos?

Last edited by Icarus2001; 16th Jun 2025 at 09:41 .
pampel
2025-06-16T09:39:00
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Post: 11903323
Originally Posted by FlyingUpsideDown
I'm not convinced the RAT is deployed. If it has deployed it could've been a last ditch effort for the crew to bring the fuel control switches from RUN to CUTOFF & back to RUN believing they've had a dual engine failure. This would account for the RAT if it did deploy.
This doesn't make any sense. The plane was in the air for approximately 30 seconds, the plane stops climbing around 12 seconds after take off, and the noise of the RAT is heard 11 seconds before the plane crashes - even if we assume the RAT both deploys instantly and deployed the exact moment that video began recording, that only gives the pilots a 7 second window to perform an action that results in it being deployed.

There just isn't enough time for the RAT to be deployed as a result of any action by the crew, IMHO. And to demonstrate how long 7 seconds is - that's enough to say 20 words, assuming no interruptions .

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Compton3fox
2025-06-16T09:41:00
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Post: 11903328
Originally Posted by FlyingUpsideDown
The PF could've been task focused flying manually, following the FD's and not expecting the sinking feeling of losing the lift. The PM has made the mistake without knowing. ie. he/she has selected the flaps all the way to UP believing that the gear was now retracting. Both pilots now think the gear is retracting, they have full thrust but are sinking into the ground. "Professional crews" like Air France for eg. have made way worse decisions. Slats are extended because they are the last to retract. I'm not convinced the RAT is deployed. If it has deployed it could've been a last ditch effort for the crew to bring the fuel control switches from RUN to CUTOFF & back to RUN believing they've had a dual engine failure. This would account for the RAT if it did deploy. The APU inlet door could've been open as well because they were carrying out an APU to Pack takeoff. Once the aircraft is airborne and the weight-on-wheels (WOW) switches indicate air mode , the main gear bogies automatically tilt to the neutral position before retraction. Also when the flaps passed the last takeoff position on the quadrant, the Landing gear configuration warning horn would've sounded further confusing the pilots.
If you read the thread, you would know:

The RAT was almost certainly deployed. 4 different sources.
The Flaps were not retracted. Visible at the accident site plus many other sources agreeing they were indeed down.
APU will autostart when all engine power is lost. Potentially explaining why the inlet door was open or partially open at the accident site. Mentioned in several previous posts
On a 787-8, the main bogies tilt as the 1st action of the gear retract sequence. As stated in previous posts. I don't think this happens unless gear is selected up. So the conclusion was, gear was selected up. One caveat, IIRC, there was some discussion around a failure could have caused the bogies to tilt without Gear up being selected but I don't recall the outcome.
As for the Air France remark, un-necessary IMHO. Let's respect the crews please.


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Airboard
2025-06-13T01:01:00
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Post: 11903706
Originally Posted by Airboard
Yes. But I have not flown this scenario in the sim. Way too many protection to take off without proper configuration which leads me to believe loss of lift due to flap retraction. 1100 hr FO \x85\x85..
I\x92ll reply to my own post in light of the RAT deployment. If true then this opens up to a lot more. And simply guessing with grainy video a fools game. All I saw was gear down to high Into the climb. This should not happen under any circumstance . Dual engine failure would explain the loss of lift obviously. Early flap retraction also. One would hope it\x92s not a simple as that: cheers
tdracer
2025-06-13T02:18:00
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Post: 11903415
Originally Posted by Sailvi767
Delta airlines had a Captain do this in 1986 on a 757 out of LAX. Came within a few hundred feet of ditching. Then flew all the way to CVG with the rat hanging out!
Not 757 - it was a 767. Second time it happened in about 12 months.

Determined to be an ergonomics problem with the switch layout in the flightdeck.

Early 767s (JT9D and CF6-80A) had a supervisory "EEC" (Electronic Engine Control - Boeing still uses "EEC" to identify what most people call the FADEC on modern engines). The procedure if an EEC 'failed' was to switch both EECs off (to prevent excessive throttle stagger - unlike FADEC, the engine could operate just fine with a supervisory EEC failed).

Problem was that the EEC ON/OFF switch was located on the aisle stand - right above the fuel cutoff switches. Turned out 'muscle memory' was when the pilot reached down there, it was usually to turn the fuel ON or OFF - which is what they did. Fortunately realizing what he'd done wrong, the pilot quickly restored the switches to RUN and both engines recovered. And yes, they continued on to their destination (RAT was still deployed since there is no way to retract it in-flight).

Previous event was with JT9D engines (United IIRC). In that case, only one engine recovered (second engine went into an unrecoverable stall), they simply came back around and did a single engine landing.

Realizing the ergonomic issue, the EECs were relocated to the pilot's overhead (retrofit by AD).

To the best of my knowledge, there hasn't been a repeat of an inadvertent dual engine shutdown since the EEC switches were relocated. It's also very difficult to 'accidentally' move the switches as there is a locking detent - the switch must be pulled out slightly before it can be moved to CUTOFF.

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tdracer
2025-06-13T05:15:00
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Post: 11903416
Originally Posted by Gin Jockey
Just as an example of how many misconceptions, mistruths, half truths and complete BS there is in this, and any accident, thread consider this\x85

I am very sure the only variant of the 757/767 that had a RAT was the 767-400, which was not in production in 1986. I flew the 767-200 and -300 with 3 different engine combinations (around 30-40 different airframes and 2 airlines) and none of them had a RAT.

Happy to be corrected if this model 757 (or 767 as someone in a later post says) had a RAT.
Sorry but you are wrong. The RAT was basic on the 767 - every single 767 built has one. The Gimli glider deployed the RAT (1982), and the Delta dual engine shutdown out of LAX deployed the RAT.

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