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Deliberate action is the most obvious and simplest answer however\x85.

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The report includes:

Quote:

. The APU air inlet door (fig. 10), which was intact, was found open.

Was the door open? Or partly open?




Was the APU inlet door screwjack opening operation interrupted - at the point of the crash? Timing the jackscrew time to operate )closed to open) would give an idea of when its automated operation began. The APU self starting becomes a time stamp of other electrical events during the pre crash sequence. Page 15 touches on this, and I think there's more to it...


The normally full open door looks more open to me than the accident airplane's apparent partly open APU door.

Subjects APU

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Quote:

Originally Posted by Diff Tail Shim

Blimey, seen a photo of the switches in question...Actually why are they not guarded?

They are guarded. To refresh everyone's memory here's a photo from the previous thread.

Subjects Switch Guards

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Quote:

Originally Posted by 9 lives

The report includes:



Was the door open? Or partly open?




Was the APU inlet door screwjack opening operation interrupted - at the point of the crash? Timing the jackscrew time to operate )closed to open) would give an idea of when its automated operation began. The APU self starting becomes a time stamp of other electrical events during the pre crash sequence. Page 15 touches on this, and I think there's more to it...


The normally full open door looks more open to me than the accident airplane's apparent partly open APU door.

Is normal on the ground sitting still the same as normal in flight at 180 knots?

Subjects APU

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Quote:

Originally Posted by nm2582

The report mentions that the immediate prior flight crew had written up a "STAB POS XDCR" status message, and that troubleshooting was carried out.
Is it possible that the troubleshooting/diagnostics left the stab cutout switches on the pedestal in the cutoff position, which went unnoticed until liftoff (i.e. upon noticing that the trim wasn't operable), resulting in a reach towards those switches, which are situated right next to the engine cutoff switches?

Like this? Actually, the middle switches should look like the port side ones IMHO. Properly guarded.

Subjects Fuel (All)  Fuel Cutoff Switches  Switch Guards

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Consider this post with a picture of the switches in question:


They must be lifted over the detent (if installed correctly) in each direction.

Quote:

Originally Posted by LTC8K6

Double pole switches. Pretty simple.You'd have to short (or open) both sets of contacts simultaneously.

One set of poles is for the circuit power, and one set is for the switch position data.

Far more than double pole - I think it's 4-8 ish. See the number of wires in the above picture. A previous post in one of the earlier thread indicated that it was essentially one pole per function - HPSOV, LPSOV, FADEC signal, generator etc. I'm not sure which one the EAFR reads. If it was a single contact failure, you would expect to see disagreement between the various systems controlled by the switch. I think that's very unlikely given both 'failed' in the same way near simultaneously and 'recovered' when switched.

For reference, it's pretty common for industrial emergency stop buttons to have 2-3 poles: redundant poles for the actual fault switching (legislative requirement above certain hazard levels), plus an additional pole for monitoring.

Quote:

Originally Posted by LTC8K6

Wouldn't they already know if the detents were missing in this case? They recovered the switches and told us what position they were in at impact.

Depends on when they identified the SB and how obvious the lack of or incorrect fitting of detents is.

Subjects EAFR  FADEC  Fuel (All)  Fuel Cutoff Switches  Fuel Cutoff Switches (detent)  Generators/Alternators  High Pressure Shutoff Valve

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Quote:

Originally Posted by Propjet88

...The report mentions that the flight crew on the immediately prior flight had written up a "STAB POS XDCR" status message, and that troubleshooting was carried out. I wonder if the scenario could be that the accident crew received a Stabiliser EICAS message on or around take-off and the Capt (who was PM) decided to action the first checklist item immediately from memory, by intending to move the Stab switches to Cutoff but moving the fuel switches instead...

Best theory I've seen so far.

Quote:

Originally Posted by tdracer

I assume the 10 second pause is based on how long it took the two 787 event pilots to realize their error and return the switches to RUN.

I assume the unusual alarm cacophony that erupted after cutting the engines would have been overwhelming. Agree an error in good faith. If bad faith were involved, the switches wouldn't have returned to the run position, or at least they wouldn't have been allowed to remain there.

Subjects EICAS  Fuel (All)  Fuel Cutoff Switches  RUN/CUTOFF

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Quote:

Originally Posted by Propjet88

I don\x92t know if the FDR measures the switch position or the electrical signal. The latter is probably more likely, although there has been much discussion around potential scenarios involving accidental switch movement as well as possible causes of electrical glitches. Let\x92s assume that the switches were actually moved, and ignoring the \x93bad faith\x94 scenario, we need a situation that encompasses the switches being moved to Cutoff by one pilot, this action being queried by the other pilot and denied by the pilot who moved the switches. For consideration, here is a possible scenario that hasn\x92t been mentioned yet and encompasses the frailty of human performance. The report mentions that the flight crew on the immediately prior flight had written up a "STAB POS XDCR" status message, and that troubleshooting was carried out. I wonder if the scenario could be that the accident crew received a Stabiliser EICAS message on or around take-off and the Capt (who was PM) decided to action the first checklist item immediately from memory, by intending to move the Stab switches to Cutoff but moving the fuel switches instead. As in all modern Boeings, the Stabiliser Cutoff switches are immediately next to the Fuel Cutoff switches and operate in the same sense (i.e. down for Cutoff). They are guarded and never normally moved but, with an intent to move the stab switches, \x93muscle memory\x94 (cerebellum activation if you prefer) may have taken the Captain\x92s hand to the Fuel switches, which are operated on every flight. The FO (who is PF) is manually flying at this stage sees and queries it. The Capt denies it, as he doesn\x92t realise what he has done (confirmation bias perhaps). After a few seconds, the terrible mistake is realised, and the fuel switches are moved back to run, but sadly too late and the Capt makes a Mayday...

A plausible theory, however, if that were indeed the case wouldn't supporting FDR data be available/have been included in the initial report?

Subjects Action slip  EICAS  FDR  Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  MAYDAY  Switch Guards

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Fuel Switches

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As a retired heli pilot I'm not going to comment. But I was interested to see the switches in question. I'm sure others will be too, so thought I would post this.

Subjects: None

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Possibility of Cut Off Switch Balanced on Gate

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Honeywell Switch Gate Configurations (Ref: honeywell_hwscs06627_1-1735572)

This extract from the datasheet of the Honeywell switch installed in the B787 for switching between Cut Off and Run shows the various gates that can be incorporated in such a switch. I suspect that it is Configuration D which allows the switch to be in one or other of only 2 positions. But the centre gate has a relatively wide flat table on which the switch can rest if it is not moved correctly to either the Run or Cut Off position. I therefore think that it is not beyond the realm of possibility that both switches may have initially been resting on the gate and then slipped into the cut off position during take off. However, what militates against this theory are the words of the challenge, "Why did you do that?" suggesting that one pilot had seen the other pilot actually flip the switches.

Subjects Fuel (All)  Fuel Cutoff Switches  Honeywell

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Well, speaking of fuel-cut switches, I read NM-18-33 SAIB with attention, and as a not-that-fluent english speaker, I stumbled on this sentence (my bold):

Quote:

If the locking feature is disengaged , the switch can be moved between the two positions without lifting the switch during transition, and the switch would be exposed to the potential of inadvertent operation.

I could hardly figure what the "disengaged" word meant in this context, so I did a Google search for the switch part numbers (especially "766AT614-3D") to figure the difference between them, and a page from this chinese web site was part of the results.

And while I was painfully crawling the thread, I noticed the following picture about an "undesirable condition":

Incorrect lock tab position on fuel cut-off switch

If this incorrect mounting is actually possible, it would possibly remain unnoticed from the pilots (normal "pull-up then move" action is unaffected), but it would cancel the protective function of the so-called "locking tab", and even limit the travel of the switch handle in both directions, making it more vulnerable to an undesired change of state.

The photos above seem convincing enough, but I'd be very grateful for an informed opinion on this assembly mistake. Even if this is possible, the probability of both switches being unexpectedly snapped seems very remote to say the least, but not as remote as previously estimated.

Subjects Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  SAIB NM-18-33  Special Airworthiness Information Bulletin

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Quote:

Originally Posted by JPI33600

Well, speaking of fuel-cut switches, I read NM-18-33 SAIB with attention, and as a not-that-fluent english speaker, I stumbled on this sentence (my bold):



I could hardly figure what the "disengaged" word meant in this context, so I did a Google search for the switch part numbers (especially "766AT614-3D") to figure the difference between them, and a page from this chinese web site was part of the results.

And while I was painfully crawling the thread, I noticed the following picture about an "undesirable condition":

Incorrect lock tab position on fuel cut-off switch

If this incorrect mounting is actually possible, it would possibly remain unnoticed from the pilots (normal "pull-up then move" action is unaffected), but it would cancel the protective function of the so-called "locking tab", and even limit the travel of the switch handle in both directions, making it more vulnerable to an undesired change of state.

The photos above seem convincing enough, but I'd be very grateful for an informed opinion on this assembly mistake. Even if this is possible, the probability of both switches being unexpectedly snapped seems very remote to say the least, but not as remote as previously estimated.

NM-18-33 SAIB left me wondering the same thing. It give a procedure for detecting the defect but omits to explain the cause. I was thinking that the wrong switches had been supplied/fitted. Assuming the image from the Chinese web site is correct, it is disappointing that the actuator can get into that state. I did not see anything that said whether that was how the switch arrived from Honeywell or if there was a defect that allowed the actuator to turn.

One other useful thing from that web site is a partial schematic which shows the connection of the 4 poles in the switch. I believe this is from a 737NG but it should be the same idea.

Subjects Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  Honeywell  SAIB NM-18-33  Special Airworthiness Information Bulletin

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Quote:

Originally Posted by DTA

NM-18-33 SAIB left me wondering the same thing. It give a procedure for detecting the defect but omits to explain the cause. I was thinking that the wrong switches had been supplied/fitted. Assuming the image from the Chinese web site is correct, it is disappointing that the actuator can get into that state. I did not see anything that said whether that was how the switch arrived from Honeywell or if there was a defect that allowed the actuator to turn.

One other useful thing from that web site is a partial schematic which shows the connection of the 4 poles in the switch. I believe this is from a 737NG but it should be the same idea.

Why are you wasting your own time?

If any of that were true why would it happen after Vr and why would one pilot ask: \x93why did you go to cutoff\x94. That is an observed deliberate action. Cmon folks enough with the nonsense!

Why are people shying around the truth!?

Subjects Honeywell  SAIB NM-18-33  Special Airworthiness Information Bulletin

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Quote:

Originally Posted by The Brigadier

It seems to me that there must have been further dialogue after the bland "I didn't". To have nothing reported after that two-line exchange, until the MAYDAY at 08:09:05, is a highly suspect omission from the interim report. In a two-crew cockpit, facing a sudden dual engine rollback just after rotation, I find it very hard to believe that this two-line exchange was the only interaction captured.

Quote:

Originally Posted by Nick H.

They are guarded. To refresh everyone's memory here's a photo from the previous thread.

Having studied human factors, that's not what I would call a switch guard. This is what I would call a guard:

Subjects Human Factors  MAYDAY  Switch Guards

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Quote:

Originally Posted by Pinkman

Having studied human factors, that's not what I would call a switch guard. This is what I would call a guard:

Having studied HF, how many flights since the beginning of time have BOTH of those switches been inadvertently moved during takeoff? If that number is 1 or less you were probably better off studying statistics.

Subjects Human Factors  Switch Guards

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If the thrust levers were found in idle but, according to the EAFR, were set to TO thrust until the end, doesn\x92t that also raise further questions? I mean: Of course, the impact causes compression at the nose, but the centrifugal forces act in the opposite direction. So, if there is an objective inconsistency here, and we have a pilot who says he did not operate the fuel cut-off switches, while the EAFR indicates otherwise, then we have yet another inconsistency.

Relevant section in the preliminary report

Subjects EAFR  Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  Preliminary Report

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Beware hindsight bias

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Quote:

Originally Posted by Pinkman

Having studied human factors, that's not what I would call a switch guard. This is what I would call a guard:

Depending on manufactures design principles, or certification standard, then the choice of switch may be determined by the result of normal operation; i.e. a reversible or irreversible outcome.

A 'unlocking' (guarded) switch, as per 787 fuel, is normally associated with normal use, but requiring a higher level of protection angainst inadvertent operation (two actions), but rarely, if at all, considers simultaneous dual operation - 2 switches.

Compare with covered / uncovered push button selections in other aircraft, and those requiring push button 'unlocking'.
A range of interchangeable words, meaning, interpretation; but the root principle is that form follows function.

Beware hindsight bias.

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Last edited by safetypee; 12th July 2025 at 13:30 . Reason: form follows function.

Subjects Human Factors  Switch Guards

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Don't the Checklist instructions for an engine restart throw a spanner in the works, in terms of what conditions you are supposed to perform the restart in? Could that account for the delay, if they were being followed? I find this:



to be very confusing, due to the Condition: statement. Having probably never actually done it before, did they think the engine speeds had to be below idle before attempting a restart?

Relevant links from previous thread:

Air India Ahmedabad accident 12th June 2025 Part 2

Air India Ahmedabad accident 12th June 2025 Part 2

Subjects Relight

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Quote:

Originally Posted by tdracer

No simulator access, but I do know this much:

One EICAS and one PFD is on the battery (most likely the left seat PFD) - they might momentarily flicker but will not 'blank'.

You get an EICAS message when you set the fuel switch to CUTOFF - something like "ENGINE X CUTOFF" (not sure of the 787 wording, but it would be something to that effect.

While I doubt the PF would be actively monitoring EICAS during TO, with the sudden audio change to the engine noise as well as the sudden loss of acceleration, I'd expect him to take a quick look at EICAS to see what the ( ) the engines are doing. Plus, if the PF was in the right seat and his PFD blanked - I'd expect him to look across to see what's on either the standby or the left seat PFC, and perhaps EICAS.

It would have been a Christmas tree of EICAS alerts

CVR should have recorded the beeper too, inhibits are for ground only.

Subjects CVR  EICAS  Fuel (All)  Fuel Cutoff Switches  RUN/CUTOFF

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My take is there is a lot of significant info purposely left out of the preliminary report. For instance, the status of the fuel cutoff switches was not mentioned. Maybe that is the info being sort by “stakeholders” and the “components of interest” that were “quarantined” were the fuel cutoff switches. “Initial leads” is also interesting.

Subjects Fuel (All)  Fuel Cutoff  Fuel Cutoff Switches  Preliminary Report

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