Posts about: "CVR" [Posts: 256 Pages: 13]

Need to identify the voices\x85. CVR should have each channel recorded separately.

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.

The switch state could be either on or off in that position. However, the CVR makes it pretty clear that the switches were moved deliberately to off. Just not why. Also, remember the report says one switch was moved then the other. Not together.

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?

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, ..)

Fwd EAFR records Cockpit Area Microphone only.

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.

I sense a hamsterwheel developing with regard to who said what and why...

If, and it remains a big "if", the switches were deliberately moved with the full knowledge of the probable outcome, given the proximity to the ground, it is not inconceivable that the question "why did you..." might have been asked by the individual responsible for having moved the switches - for the sole purpose of ensuring that any subsequent CVR evidence inferred that the action had been undertaken by the occupant of the other seat. Therefore the reply "I didn't" would in such circumstances be entirely accurate/genuine.

There is little to be gained here unless/until more evidence is forthcoming. Doesn't the 787 have flight deck CCTV?

Neither pilot was likely speaking in order to be recorded for posterity, so that 'conversation' makes perfect sense in a situation where there is high stress and a great deal of confusion.

As to the report not closing off speculation, that isn't it's purpose. It is there to report the facts as they are found. It must also be said that speculation is not in any place but the eye of the beholder.

That's the case when the EAFR is being powered by the independent power supply. In normal circumstances, all the CVR channels will be recorded.

Well, it\x92s narrowed it down to 3 possibilities:

Action slip
SAIB NM-18-33
Intentional.

Those switches are lift to move. They were lifted to shut off and thrown back to start in the report. No CVR or FDR trace is going to explain why two switches were throw by error or by intention. Only a video would. PnF would have had his eyes outside or on instruments for the calls. As mentioned, other manufacturers put such switches out of harms way for general use. QRH is the only reason to go to them.

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 actual CVR will be crucial to solving the problem.

When someone attempted the engine re-lights at 08:08:52 and 08:08:56, does the CVR hear one or two movements of the RUN/CUTOFF switches for each engine?

Therefore, we could determine the position of the switch prior to the re-light attempt, and whether this was caused by a person on the Flight Deck or mechanical problem.

Release the CVR.

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!

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).

It seems like people are jumping to conclusions about the pilots and letting Boeing off the hook without proper investigation. Instead of providing a professional, detailed transcript of the cockpit voice recorder (CVR), we\x92re just getting casual comments about what the pilot allegedly said. Critical information\x97like the timing of transmissions, the checklist items completed before takeoff, and other key details that should be on the CVR\x97are essential for understanding what happened in the cockpit, especially since the crash occurred so soon after takeoff. In my view, the preliminary report feels too convenient for certain parties involved.

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.

This is a preliminary report. It is quite detailed for a preliminary report.

Examining the before-takeoff checklists seems like it would be akin to examining the re-arrangement of the deckchairs before the titanic even hit the iceberg.

The engines were switched off. Unlike Embraer, B & A have no protections stopping you switching an engine off inadvertently. From everything in the report, everything operated exactly as designed. I am not certain of how long the relight window is without windmilling speed, but +- 10 seconds seems entirely reasonable.

The outstanding question that presumably requires much more in-depth investigation of the wreckage items and CVR audio is whether:

• the cutoff switches were operated deliberately (and by who)
• the cutoff switches were operated inadvertently (and by who)
• the cutoff switches were bumped (by what) and the guards failed or weren't installed
• some electrical failure perfectly mimicked both many-pole switches being operated, then being operated again (seems unlikely)