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

OK, a couple of informed comments, again with the disclaimer that I have very little first hand knowledge of the 787.

Every single engine parameter I've seen on a DFDR readout has been recorded at 1/second (most parameters), or slower. I've never seen an engine parameter recorded at more than once/second.
The recorder doesn't do an instantaneous snapshot - it cycles through the thousands of recorded parameters. So a once second difference on the data could - in reality - be anywhere from 0.01 seconds to 1.99 seconds. If it matters, a deep dive into the avionics and FDR logic could narrow that time interval down. That being said, moving both switches to cutoff could happen in about a second. The switches make a rather distinct noise (especially if moved rapidly) so the CVR should give better resolution.

There have been instances in the past where the locking tab on the switch has been broken or 'worn down' from heavy use. But that's been seen on very high cycle aircraft - usually 737s that fly short hops. No memory of ever hearing of an issue with relatively new 787s that are - by nature - long range aircraft and don't get a lot of cycles.

On the 747-400, the fuel switches are a 'break before make' design with a distinct gap of ~0.050 seconds during a normal switch cycle (it's a long, somewhat painful story about why I know that...). I don't know the specifics of the 787, but I'd be very surprised if it's any different.

BTW, if the investigators had reason to believe the switches somehow moved on their own, I think a fleet wide inspection would have been ordered by now.

I keep coming back to my 'muscle memory' hypothesis...

The report states that "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" . It doesn't say at the start of the paragraph but if following from the previous paragraph then this information is sensed from the data recorder.

Again, from the report "As per the EAFR, the Engine 1 fuel cutoff switch transitioned from CUTOFF to RUN at about 08:08:52 UTC. The APU Inlet Door began opening at about 08:08:54 UTC, consistent with the APU Auto Start logic. Thereafter at 08:08:56 UTC the Engine 2 fuel cutoff switch also transitions from CUTOFF to RUN.". Again this is sensed from the data recorder.

I would be interested to know whether sounds consistent with the actual fuel control switch being moved have been picked up on the voice recorder.

Thus the lengthy sticky thread on "shutting down wrong/both engines." Brain farts happen.

I don't think it's ridiculous to suggest that perhaps one crew intended to manipulate a different control (stab trim cutout?) and flipped the fuel cutoff instead, maybe not even realizing what has happened. Sure, unlikely, but essentially every aspect of airline accidents is unlikely.

The photo of the engine switches in the report shows the toggle of both switches pretty clearly, with the caps burned off (to be expected, has zero effect on function, nor detent locking). The fact that the toggles and lower mechanism of each switch appears in the photo is pretty conclusive (a) to the position of the switches at the time of crash, and (b) that the locking detent function of the switch was functional as intended. I've worked with these switches for decades, and they are very robust. Their lesser cousin design, which also has a center detent lock position (double throw) are less robust that these (single throw) switches, and they last well too. Though I have seen them worn, I have never seen the locking function worn to the point of not functioning as a lock. And these switches would be too new to have experienced wear/damage to that point.

For myself, I have total confidence that the switches functioned as intended. Obviously they commanded the fuel valve as intended, and can be seen intact (other than the plastic caps), and in the run position, so it is safe to conclude that a mechanical/electrical fault of both independent switches at the same moment is unlikely in the extreme. The FDR data states that they were moved to "off" position, which caused the engine shutdown, then returned to "run", so they obviously were mechanically and electrically functional.

The automatic deployment of the RAT is an indicator of the airplane systems sensing an engine shutdown, as is the APU autostart. Pax 11A mentioned the green cabin lights, which, if I understand correctly is an indication of a complete electrical generation failure.The time of all these events can be plotted from recorded data, which I expect we'll see in a full report later. In the mean time, it all makes unfortunate sense.

I am going by the list in the excellent post here: Air India Ahmedabad accident 12th June 2025 Part 2

Anyway, here goes:

A. Misconfiguration or wrong takeoff data — OUT : 5 tons under MTOW, flaps 5, takeoff roll uneventful

B. Flaps retracted post-takeoff instead of gear — OUT : flaps 5 still set at crash

C. Low-altitude capture — OUT : throttle was at take-off thrust the whole time

D. Loss of both engines at or shortly after rotation — IN: confirmed to have occurred 3-4 seconds after liftoff

I. Bird strike/FOD — OUT

II.Fuel-related
1. Loss of electric fuel pumps — OUT
2. Fuel contamination — as good as OUT , but lab work is ongoing
3. Vapour lock — OUT

III. Improper maintenance — mostly OUT , switches might have been defective

IV. Large-scale electrical fault (e.g. due to water in E&E bay) — OUT . This would have been obvious from the flight recorder.

V. Shutdown of engines by TCMA — OUT . Conditions not met (not on ground, throttle not at idle)

VI. (Inadvertent) shutdown by flight crew
1. Spontaneous execution of memory items (fuel control switches OFF, then ON; deploy RAT) due to assumed engine malfunction — OUT from CVR
2. No indications whatsoever of an intentional shutdown for nefarious reasons — IN but unsupported

VII. Malfunction/mishandling of the fuel cutoff switches (most recent)
1. Wear or improper operation of the switches, so that they do not lock but can shift back into the OFF position. — IN

Read the previous post to this by 9 lives and reconsider VII.1
Senior Pilot

2. Spilled drink leading to short in the wiring — IN (barely) , 8 separate switch contacts must be affected in just the right way

If you never supported any of the theories that are now out, pat yourself on the back!

You should ask Honeywell to correct their data sheet.

Why don't you read the data sheet for the switch series and count the number of references to "toggle switch" in the description.

https://octopart.com/datasheet/4tl83...ywell-25749542

Boeing has put the fuel control switches in more or less that same position starting with the 707 (it may go back even further). Over a billion flight cycles on 707, 727, 737, 747, 757, 767, 777, and 787 (not to mention various military installations such as the KC-135.

Baffled, as probably all of us. But 10 seconds between \x93cut-off\x94 and \x93run\x94 is not excessive imo:

08:08:42 - max speed
08:08:43 - cut-off eng 1
08:08:44 - cut-off eng 2; run-down eng 1
08:08:45 - run-down eng 2
08:08:46 - startle moment
08:08:47-48 - instruments, levers and switch scan
08:08:49-50 interrogate other pilot why he moved switches
08:08:51: other pilot denies
08:08:52: eng 1 fuel switch to \x93run\x94
08:08:53: it\x92s both fuel switches that were cut off
08:08:56: eng 2 fuel switch to \x93run\x94

You are absolutely correct insofar that is the most likely explanation, but see answer above. While I have found, as I suspect most, the deliberation angle most likely, since day one, it isn\x92t really fit for discussion, so the other, admittedly slightly more unlikely avenues are more appropriate and more interesting imho.



But you also underestimate my history with spilling coffee on large amounts of switches, but while tangentially relevant, that is for another thread in another forum.o-)

Intermittent faults with spillage and switches fixed by cycling/fiddling is a thing, and it is not contrary to the facts from the report. It is possible. It is also, admittedly not the most likely.

Exactly, the report said transitioned, not moved. The report just says the recording shows change of status, it does not imply deliberate action to change it.

Repeat of request.

Timeline of known events with source attribution from the preliminary report:

08:07:33 ATC: Takeoff clearance
08:07:37 A-SMGCS: Aircraft starts rolling
08:08:33 EAFR: V1 153kts
08:08:35 EAFR: Vr 155kts
08:08:39 EAFR: Gnd-Air mode transition
08:08:42 EAFR: Max IAS 180kts, Eng 1/2 Cutoff switches activate within 1 second of each other
08:08:42 CVR: "Why did you cut off", "I did not" (exact time not specified)
08:08:42 A-SMGCS: RAT deployed (exact time not specified)
08:08:47 EAFR: Both engine N2 below min idle. RAT hyd pwr commences
08:08:52 EAFR: Eng 1 cutoff to RUN
08:08:54 EAFR: APU inlet door opens (auto start logic)
08:08:56 EAFR: Eng 2 cutoff to RUN
08:09:05 ATC: Mayday call
08:09:11 EAFR recording stops

Fuel cutoff switches operated within 1 second of each other suggests to me that the locking mechanism wasn't working as per (SAIB) No. NM-18-33. Any loose item could have accidentally (or not) operated the switches (including hands).

I\x92ve been on the 787 for over a decade. The deliberate movement of the cut-off switches shortly after V2 was the only logical, simplest explanation. The motivation of which, I\x92ll leave to others to figure out.

If I recall correctly, the Mayday call was wording to the effect "thrust not achieved". That sounds like a phrase which could be expected from a pilot who had just frantically tried to restart an engine, and realized that it was not a success, and there would not be an opportunity for another attempt. The pilot aviated, (forget navigation), then communicated - over a period of 13 seconds.

Is it time for a \x91are you sure about that?\x92 Prompt for select serious config changes?

My computer asks me that when clicking \x91delete\x92 on a file.

the way everything is integrated now - the airplanes are pretty good at knowing what\x92s \x92normal\x92

selecting cutoff on the engines while in ground mode could be considered normal, but while flying it could sure use a second verifying prompt.

The report says:
"The other pilot responded that he did not do so."

Exact wording is not provided, so maybe it was "what the hell are you talking about?" or maybe it was "I didn't". If I was the FO and the Captain asked "why did you cutoff?" and I hadn't, I would reply "I didn't". If the conversation was in the other direction it might be different.

No doubt expert analysis of the voice recording is underway.

The prompt is me sitting next to said persons cutting the switch saying \x91what the heck are you doing\x92.

I'm bewildered by the descriptions of the toggle switches. 'Lifting' is not the terminology I've lived with. The knob is pulled out so that the detents in the inner end of the knob can move over the sharp ridges on the switch body. A minor point, but what is not so minor is the inference that these detents and ridges are a safety design that is sometimes not installed. Surely, they must be talking about some further mechanism, or am I in the twilight zone? I cannot believe there's an aircraft with simple smooth action between off and on, an over-centre toggle . . . that will stop the engines!

The DC3 had fuel levers, the right two of six on the pedestal. We had to put our hand across the slots when selecting the mixture, so that our other hand wouldn't pull the lever to cut out. 60 years later there's a toggle that can be jogged to off?!

I'm not ready to accept the time-line. My FO's were not as highly trained and the aircraft much simpler, but I'd track what they were doing every second until I'd got comfortable airspace under me. Reaching out and stopping the engines? Asking why? What world are they living in?
WTFH!!!!!? followed by the switches being back on. I really don't think I was that much different to my colleagues - they'd darn soon react to fairly modest mistakes, let alone chopping the fuel.

I know the language and basic quotes are not necessarily as written, and trying to take into account the surreal predicament the 'other' pilot found himself in, but what I'm reading doesn't set the scene for an experienced skipper that's also a trainer being the one that's surprised by his colleagues action.

Can someone with the engineering knowledge build a timeline/timeframe for fuel cutoff switch RUN to CUTOFF -> fuel stops -> engine flameout -> N2 drops to ? -> VFSGs quit -> RAT deployment starts -> RAT full power -> APU deployment start?
Does the RAT really start providing power in 4 seconds from the E2 fuel cutoff switch RUN -> CUTOFF?


Timeline from AAIB and the public CCTV video:

08:08:33 v1 153 kts
.
08:08:35 vr 155 kts
.
.
.
08:08:39 Liftoff, A/G Air Mode, rotation at 00:18 in public CCTV video
.
.
08:08:42 E1 Fuel Cutoff Switch RUN -> CUTOFF, 180 kts
08:08:43 E2 Fuel Cutoff Switch RUN -> CUTOFF
.............? N1 N2 begin to decrease
.............? "Why did you cutoff", "I didn't"
.............? Airport CCTV shows RAT
.............? N2 < idle speed
08:08:47 RAT hydraulic power
.
08:08:49 Public CCTV video: visible loss of thrust, Alt < 200ft using wingspan
.
.
08:08:52 E1 Fuel Cutoff Switch CUTOFF -> RUN, CCTV video: visible descent
.
08:08:54 APU inlet door begins opening
.
08:08:56 E2 Fuel Cutoff Switch CUTOFF -> RUN
08:09:05 MAYDAY
08:09:11 EAFR Recording stops
08:14:44 Crash Fire Tender leaves airport

My only question is, after close to 40 years flying, on takeoff, if I lost thrust/ Power, my immediate reaction would NOT BE TO CHECK THE FUEL CONTROL SWITCHES. Unless the Pilot flying saw the Pilot monitoring visually reach down and shut the fuel control switches off, which would be odd since as the PF, your attention is looking at the instruments and outside, not inside and downward in the direction of the FC switches. It seems odd how quickly they ascertained the fuel control switches were shut off. No startle factor, or confusion, just a very quick determination that the FC switches were cutoff. Very strange.