Posts about: "Fuel (All)" [Posts: 1005 Pages: 51]

Dual engine failure due to fuel contamination?

or birds?

True. We won\x92t know until the CVR and Flight Data recordings have been analysed. I think these will give a clear indication of what happened. The airport has reopened so I assume there\x92s no fuel contamination risk.

Fuel contamination?

That was my first guess

A dreamliner can cope with multiple failure scenarios on take off but fuel contamination isnt one of them

options
Serious pilot error (retracting flaps etc)
fuel issue
birdstrike
some new latent technical common issue in engine control systems

Medical episode on flight deck resulting in sedrious pilot error?

Like the dual engine failures that occurred on every aircraft which took off before it, using the same fuel supply?

😩

Symmetric is the key word.

The chances of both engines having simultaneous flame outs due to fuel contamination is almost not possible...too many variables to have them fail at the same time.

What we are seeing is a fairly stable flight path....in that the wings remain level throughout and a point in the flight where the vertical profile changes from a normal take off flight path into the high nose attitude descending one...albeit without any significant or abrupt maneuver.

Strange.

Heathrow 777?

Possibly yes. The single-aisle, non-ETOPS and 30 yrs older design I am familiar with has a cutoff speed of 140 kts. V2 for 98% real-life scenarios is higher than that. No reason for the 787 to be any less capable.

I don't see a problem with questions and people of any level of qualification can provide factual information. Questions can be answered and misstatements can be corrected. That said, better quality input is always welcome, but at this stage we're not likely to get much professional or official input. I hope the Indian authorities are transparent here and I think it is likely we'll have plenty of data.

IMO the problem is the relentless comments by people that apparently think they will win something by cracking the case or "calling it first" or those that can look at some AI rendering of a blurry picture and conclude they know the flap settings. Or concluding that a likely cause for this crash was that both engine master switches were turned off.
Of course dual fuel cutoff is a remote but possible answer, but not one worth speculating about at this point let alone concluding that's what happened.

That was my first thought. You don\x92t get a double engine failure for nothing else but that and maybe birds, but birds would have caused some trailing smoke or at least some visible signs on cctv at some point throughout the ingestion period.

OK, I promised some informed speculation when I got back, so here goes:
Disclaimer: never worked the 787, so my detailed knowledge is a bit lacking.

First off, this is perplexing - especially if the RAT was deployed. There is no 'simple' explanation that I can come up with.

GEnx-1B engines have been exceptionally reliable, and the GE carbon composite fan blades are very robust and resistant to bird strike damage (about 15 years after the GE90 entry into service, I remember a GE boast that no GE90 (carbon composite) fan blades had needed to be scrapped due to damage (birdstrike, FOD, etc. - now that was roughly another 15 years ago, so is probably no longer true, but it shows just how robust the carbon composite blades are - far better than the more conventional titanium fan blades).

Not saying it wasn't somehow birdstrike related, just that is very unlikely (then again, all the other explanations I can come up with are also very unlikely ).

Using improper temp when calculating TO performance - after some near misses, Boeing added logic that cross-compares multiple total temp probes - aircraft TAT (I think the 787 uses a single, dual element probe for aircraft TAT, but stand to be corrected) and the temp measured by the engine inlet probes - and puts up a message if they disagree by more than a few degree tolerance - so very, very unlikely.

N1 power setting is somewhat less prone to measurement and power setting errors than EPR (N1 is a much simpler measurement than Rolls EPR) - although even with EPR, problems on both engines at the same time is almost unheard of.

The Auto Thrust (autothrottle) function 'falls asleep' at 60 knots - and doesn't unlock until one of several things happens - 250 knots, a set altitude AGL is exceeded (I'm thinking 3,000 ft. but the memory is fuzzy), thrust levers are moved more than a couple of degrees, or the mode select is changed (memory says that last one is inhibited below 400 ft. AGL). So an Auto Thrust malfunction is also extremely unlikely. Further, a premature thrust lever retard would not explain a RAT deployment.

TO does seem to be very late in the takeoff role - even with a big derate, you still must accelerate fast enough to reach V1 with enough runway to stop - so there is still considerable margin if both engines are operating normally. That makes me wonder if they had the correct TO power setting - but I'm at a loss to explain how they could have fouled that up with all the protections that the 787 puts on that.

If one engine did fail after V1, it's conceivable that they shut down the wrong engine - but since this happened literally seconds after takeoff, it begs the question why they would be in a big hurry to shut down the engine. Short of an engine fire, there is nothing about an engine failure that requires quick action to shut it down - no evidence of an engine fire, and even with an engine fire, you normally have minutes to take action - not seconds.

The one thing I keep thinking about is someone placing both fuel switches to cutoff immediately after TO. Yes, it's happened before (twice - 767s in the early 1980s), but the root causes of that mistake are understood and have been corrected. Hard to explain how it could happen (unless, God forbid, it was intentional).

No\x85
Certain jet fuel types may not be authorized for use by the manufacturer but the engines would still run.
Jet engines can run on (almost) anything.
its not like Jet A into a piston engine.

https://assets.publishing.service.go...211_G-POWN.pdf

One example of fuel contamination causing a significant loss of thrust on both engines at low altitude.

But it seems extremely unlikely for contaminated fuel to impact both engines at exactly the same time, with no asymmetry and no surges or smoke.

What can cause a sudden catastrophic loss of thrust on both engines at exactly the same time?

Birds (but no apparent surges)

Inadvertent movement of the fuel cut off switches (which would be an incredible error but I suppose it could conceivably be muscle memory having done so recently after the last leg\x85weirder things have happened. Remember the 767 events of the late 80s)

Intentional shutdown of the engines (pilot suicide has happened before)

Some catastrophic electrical/FADEC/engine interface failure (which I highly doubt is feasible in a modern 1309 aircraft)

I can\x92t think of any others\x85

About the only way that could happen would be some catastrophic software 'hole' in the GEnx-1B FADEC software. By design, the only thing the engine control really needs to adequately the engine is:
1) Fuel
2) Thrust lever position
Everything else is 'goodness'. The FADEC has its own dedicated (gearbox mounted) electrical generator (actually alternator), so even a 100% aircraft power loss wouldn't affect the FADECs ability to control the engine. It was right at takeoff - 'suction feed' would be more than sufficient if the aircraft fuel pumps failed, FMC and other aircraft inputs have only a secondary effect on the thrust setting, it's primarily determined the thrust lever position.
So there is no known way that a fault in the engine/aircraft interface could cause a large loss of thrust.

Can someone smart on the 787 answer this: What protections and indications does the crew have if the boost pumps aren\x92t turned on? Can the engines start with them off? I know jet engines \x93should\x94 suction feed but rotation and dual flameout could be explained by pump issues.

From the airport CCTV video it looks to me like a normal takeoff and start of climb, until suddenly there's a loss of climb performance with no obvious upset at that point. From the picture of the wing post crash it looks like the flaps were still deployed (N.B. based on pre-accident photos that's the right wing so closest to the camera is aileron and flaps are further away, damage had me confused first time), so I'm going with loss of thrust rather than flap retraction.

From the videos from bystanders it looks like RAT deployment (both sound and zoomed in pictures) rather than thrust lever retard, and that would also explain failure to retract gear - if you are dealing with both engines out at that altitude then gear isn't your first thought. From the airport CCTV video I don't see anything that looks like bird strikes at that point in the climb i.e. no obvious flocks of birds, no smoke out of the engines, no slewing one way as one engine fails and then the other is cut by accident - plus you wouldn't cut the engine at that point, you'd climb on one engine and then sort it out.

Even fuel contamination or water build up in both tanks is likely to result in one engine failing a few seconds before the other. So I can't come up with anything other than both fuel cutoff switches that would result in loss of thrust and RAT deployment. Looking at a picture of the cutoff switches https://www.nycaviation.com/2013/08/...is-fired/30179 I don't see how they get hit by accident.

I'm confused, hope we get an FDR / CVR readout soon.

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.