Posts about: "Fuel Cutoff Switches" [Posts: 827 Pages: 42]

it would have to be small enough to fit between the idle throttle position and guards on each side of the switches and weigh enough to push the switches over the detent, unless the SAIB cones into play.

The report proved that occams razor was right. Fuel switches acted which was the simplest explanation. And occams razor will not allow for a 15000h line check captain as PM to need over 10 seconds to reset fuel switches while both engines spooled down from TO thrust to sub idle within 5 seconds.

There is mention of fire damage or thermal damage to the centre pedestal, perhaps enough to identify the position of the switches but not to be able to determine their internal physical state relating to the detent mechanisms.

The Boeing 717 had a near identical Fuel Switch setup.

An Australian crew once had a Tech Log folder fall off top of the Instrument Shroud and land on a fuel switch which initiated a shutdown. This was at altitude so unlike this incident there was time to troubleshoot and recover the engine.

Australian registered B717s were then required to install a guard above the fuel switches to help prevent anything that falls on them from bumping them to the Off position.

Interestingly there was also a requirement to \x91jiggle\x92 the fuel switch after selecting it to ON after start to ensure it was seated correctly and wouldn\x92t accidentally flick to OFF due to it not being fully in the ON Position.

Yes, which is why I said a small such range of objects. I can't see how both switches could unintentionally be moved individually one after the other unless there was something wrong with the detent mechanisms. I suppose a careless hand is also a possibility, removed from the thrust levers on rotation?

Even the 20,000 hour Sully needed 7 seconds to select the ignition switches to start, 12 seconds to take control and a whopping 17 seconds to call for the QRH checklist.

Yet seconds later the transition from CUTOFF to RUN was recorded and was effective for both switches. "Effective" means all poles made contact, the spar fuel valves and EECs. Independently, on each side. We know this because both engines re-lit at different times.

Doesn't sound like spilled coffee or "a short."

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.