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

So, yes, switches.
either
1/deliberately cut off by someone in the cockpit, or
2/placed in an intermediate gate position possible due to wear or wrong installation, happens during engine start, and then vibrates or bumps to cut-off during the take off roll or
3/some kind of liquid or other contamination in the LRU shorting both and cycling them after 8 seconds brought them electrically back to RUN.

Anyone got other ideas?

FAA issued an SAIB in 2018 about these fuel control switches being installed without the locking feature engaged\x97Air India didn\x92t act on it (not mandatory).
No evidence of birdstrike, fire, or mechanical failure. Both engines had good health data. The only obvious explanation at this stage is an inadvertent dual shutdown by crew,

Ready to talk about the current Embraer method of respective throttle must be at idle to allow the fuel cutoff switch to send a cutoff signal?

That's where I was going in the last page of the last, closed thread.

Wear and tear, off by mistake, off by ill-will, off by cockpit FOD flying about at rotation, no effect with throttle forward.

I don\x92t think we can rule out deliberate based on this report surely and the lack of emergency bulletin being issued is quite telling is it not?

then again this isn\x92t all pointing at the pilots which is interesting

Is option 2 possible? It was my idea too but does the switch "connect" when it is not properly in its guarded possition?

That “I didn’t” on the CVR doesn’t sit right. If the cutoff switch movement was accidental, one would expect shock, confusion, or immediate troubleshooting, not a flat denial.

We are talking about the Engine 3 position stop/run/start switches here? SB stopping engine shut down if thrust lever are beyond flight idle? Blimey, seen a photo of the switches in question. Assume they are detented? Actually why are they not guarded?

Not really. It might also indicate that he saw them move, knew his hands were somewhere else, or a plethora of other reasons. Even if one accidentally moves a lever or pushes the wrong button, the first response would likely be denial as well, then followed by an 'oh oops, turns out I did'.

I assure you, if both donkeys start rolling back and the other guy asks why I closed the masters when I hadn't, that fact is extremely likely to verbalised.

I would look at this from the other way and suggest it doesn't sit right as if someone had just done it deliberately, seconds after rotation, why would they bother denying it, if you see what I mean?

10 seconds from challenge to switching the fuel switch back on? Would it not be an immediate act?

The exact quote was

"The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec."

Does anyone know what the sampling frequency of the data is? If we get one readout per second, then it's possible that a one second difference could only be a millisecond difference in real life, which doesn't necessarily rule out an accidental bump.
If there truly was a second of difference, there aren't many other options than an intentional act. Not necessarily with the purpose of crashing the plane though (confusion, hallucination, distraction, ..)

I remember the SAIB. I assessed it as “recommended” to all our customers and all agreed. I then raised work orders to check all fuel cut-off switches for the missing locking bar conditions. None were found defective. The preliminary report says the switches were found in the Run position. There is no mention of whether the locking mechanism is correctly in place. We need to wait for the full report for that, as this matter is still under investigation.

The phrase in the report is "switches transitioned from RUN to CUTOFF position".
Does the FDR actually have some input of the physical position of the switches or is it just measuring the output signal voltage
which might be changed by a momentary short from liquid or swarf.
Both signals go to cutoff within 1 second but then one recovers four seconds after the other.
Surely a pilot discovering a turned off switch would have both back on in less than four seconds.

Are there any switches that would normally be selected/ moved immediately after take off? The suggestion being that if they were moved due to a conscious act, the wrong switches were selected inadvertently. I am not suggesting that the switches might not still have moved for other reasons eg wear, not properly gated? But for both switches to move from Run to Cut Off within a few seconds of each other suggests a deliberate, if accidental, selection? God forbid if it was a deliberate, intentional action😞 For a member of the crew to identify, so quickly, that the two switches had been moved and then reinstated them was, I would suggest, miraculous\x85..unless the incorrect switch selections had been observed\x85\x85\x85

Again, you can not conclude that from the report.

Different inputs are sampled at different rates. Some very basic info here: https://scaledanalytics.com/2023/04/...uses-767-data/

It's highly likely switch positions are only sampled at 1Hz, and not at 100 Hz. For engine parameters you'll likely want a higher sample rate, as the whole engine could go from perfectly fine to exploded in less than a second.

If you had something like:

08:08:42.96 UTC: cut off switch 1
08:08:43.01 UTC: cut off switch 2

It would likely be recorded as:

08:08:42 UTC: cut off switch 1
08:08:43 UTC: cut off switch 2

Leading you to believe there was one second between these 2 actions, whereas it was actually only 50ms.

The Fuel Cut Off switches on a 787 have to be pulled up (out of \x91run\x92) and whilst held up, they are then moved backwards to the \x91cut off\x92 position. They are designed this way so loose objects can not move them to cut off. They can only be selected to cut-off by pulling and moving rearward in the same movement.

I think most line pilots, upon noticing that the fuel levers were in cutoff right after rotation, would immediately turn them back on. I don't think it would take 10 seconds--or even 5--to get that handled as I imagine most professional pilots would quickly grasp the seriousness of the problem. The only explanation I can think of for even that short delay--one that may have made a big difference--is the authority gradient between Captain and FO. But the preliminary report doesn't give us the level of detail we'd all like to have so it probably isn't possible to 100% support any specific conclusion just yet.

Agreed, it's most unfortunate that that the preliminary report hasn’t closed off speculation, it's simply created opportunity for more.

It confirms that both fuel cutoff switches were moved to OFF at Vr, within a one second interval which is as extreme and inexplicable as it gets. Then it gives us a CVR quote that’s so neutered, "Why did you cut off?” / “I didn’t”, that it raises more questions than it answers. If the goal was to reassure or clarify, it’s had the opposite effect.

That's a very good question.

Actually, why are switches that are only really required on the ground or in an engine shut down event where they are? Embraer's have the switches out of the way on an overhead panel and as well as detent locked, have a protective guard, one has to physically lift. If the PF had to physically carry out the engine shut down on an Embraer, he would have to raise his arm. Would be obvious to the PnF.