July 09, 2025, 23:20:00 GMT
permalink Post: 11918695
There has been discussion recently about a procedure that involves moving the fuel switches to CUTOFF and then back to RUN following a dual engine failure.
Attached is an image of a page from the Air India 787 Training Manual that discusses this procedure.
I am submitting this without comment or opinion.
Attached is an image of a page from the Air India 787 Training Manual that discusses this procedure.
I am submitting this without comment or opinion.
July 10, 2025, 09:59:00 GMT
permalink Post: 11918893
Ex 787 pilot here, I can confirm that the excerpt from the FCTM above is correct, and also confirm that the QRH memory items for Dual Engine Fail/Stall are:
Condition: Engine speed for both engines is below idle
Fuel Control Switches (both) \x85 CUTOFF then RUN
RAM AIR TURBINE switch \x85 Push and hold for1 second
Condition: Engine speed for both engines is below idle
Fuel Control Switches (both) \x85 CUTOFF then RUN
RAM AIR TURBINE switch \x85 Push and hold for1 second
July 10, 2025, 11:14:00 GMT
permalink Post: 11918946
Ex 787 pilot here, I can confirm that the excerpt from the FCTM above is correct, and also confirm that the QRH memory items for Dual Engine Fail/Stall are:
Condition: Engine speed for both engines is below idle
Fuel Control Switches (both) \x85 CUTOFF then RUN
RAM AIR TURBINE switch \x85 Push and hold for1 second
Condition: Engine speed for both engines is below idle
Fuel Control Switches (both) \x85 CUTOFF then RUN
RAM AIR TURBINE switch \x85 Push and hold for1 second
July 10, 2025, 15:53:00 GMT
permalink Post: 11919101
That does not mean that the pilots "out of habit" would have reverted to the procedure. Who would not? But in that case, the fuel control switches would be found in the RUN position post crash (if anything was left). So did they find the switches in the cutoff position, or did the action of switching got "stored" somewhere in FDM (not a specialist on these things, only to hear many times in the past that "maintenance is already aware" if we had an issue and called maintenance post flight)
July 10, 2025, 16:08:00 GMT
permalink Post: 11919112
With the recent (albeit unofficial) indications that both engine fuel control switches were found in the CUTOFF position, I wonder if it's time to reassess the tone and meaning of Captain Sabharwal's final transmission (perhaps translated from Hindi) “Thrust not achieved… falling… Mayday! Mayday! Mayday!”
Viewed in light of the reported switch positions, the phrasing feels increasingly ambiguous. As is often stated on PPRunE, communication comes after aviation so you wonder why in the crisis and at low altitude, this message was transmitted. Being so atypical, the message merits re-examination.
Viewed in light of the reported switch positions, the phrasing feels increasingly ambiguous. As is often stated on PPRunE, communication comes after aviation so you wonder why in the crisis and at low altitude, this message was transmitted. Being so atypical, the message merits re-examination.
July 10, 2025, 16:30:00 GMT
permalink Post: 11919130
With the recent (albeit unofficial)
indications that both engine fuel control switches were found in the CUTOFF position
, I wonder if it's time to reassess the tone and meaning of Captain Sabharwal's final transmission (perhaps translated from Hindi) \x93Thrust not achieved\x85 falling\x85 Mayday! Mayday! Mayday!\x94
Viewed in light of the reported switch positions, the phrasing feels increasingly ambiguous. As is often stated on PPRunE, communication comes after aviation so you wonder why in the crisis and at low altitude, this message was transmitted. Being so atypical, the message merits re-examination.
Viewed in light of the reported switch positions, the phrasing feels increasingly ambiguous. As is often stated on PPRunE, communication comes after aviation so you wonder why in the crisis and at low altitude, this message was transmitted. Being so atypical, the message merits re-examination.
July 10, 2025, 16:33:00 GMT
permalink Post: 11919132
Given that it would have been obvious to the crew very late on that they were going down, might the switches being set to CUTOFF be a last ditch measure to try to prevent a post-crash fire?
July 10, 2025, 16:38:00 GMT
permalink Post: 11919135
That said, switches found in the RUN position don\x92t generate investigative focus, they're assumed to be where they should be. The mere fact that the fuel switches are attracting attention implies there's something abnormal.
July 11, 2025, 00:34:00 GMT
permalink Post: 11919310
This has all been answered in previous posts, but I'll repeat it for those you don't want to look back through something like 150 pages:
Thrust Lever Angle (TLA) is measured directly by the FADEC, using a resolver hardwired to and excited by the FADEC. Both FADEC channels have their own resolver input - on most Boeing aircraft it's a common resolver with two sets of electrically isolated windings, however on the 787 it actually uses two mechanically separate resolvers. The resolver is basically read as "sine" and "cosine" which is converted in the angle. This also makes error detection easy, using the sine squared + cosine squared relationship. Any other aircraft systems that use TLA use the TLA signal relayed back to the aircraft by the FADEC.
The fuel control switch is a two-position multiple pole 'latching' switch - you have to pull it out slightly over detent to move it between the RUN and CUTOFF positions (on other aircraft there is an interposing relay for some of the functions. not sure about the implementation on the 787). Moving the switch to cutoff sends a DC signal to both the High Pressure ShutOff Valve (HPSOV) in the fuel control and the spar valve commanding them to close. HPSOV is solenoid actuated and is near instantaneous, Spar Valve takes ~one second to change positions (yes, this is different than some other airframers that only send the signal to one valve or the other, but it's been standard Boeing design practice since the early 1970s). Both the HPSOV solenoid and the Spar Valve are designed to stay in their last commanded position if airframe power is lost. Moving the switch to CUTOFF also sends a 'reset' signal to the FADEC - meaning the FADEC will be offline for roughly one second. On the 787 (and 777 and 747-8), there is a brief pause (~0.25 seconds) before the shutdown signal is sent to the engine to allow the electrical system to reconfigure to prevent a brief interrupt of electrical power to the rest of the aircraft.
Pulling the Fire Handle does the same thing as the fuel condition switch - via separate wiring (physically isolated from the fuel switch wiring to help protect from things like rotor burst damage), with the exception of the FADEC reset (since there is no requirement to be able to restart the engine after a Fire Handle shutdown).
There is absolutely no TLA input into either the fuel conditions switch or the Fire Handle - you can shutdown the engine via either regardless of Thrust Lever Angle.
All this is standard Boeing design practice (and except for the no-break electrical power transfer) has been for at least 50 years. This is enforced by the Boeing "Design Requirements and Objectives" - DR&O - compliance with is demonstrated by an audit after the final design freeze.
Thrust Lever Angle (TLA) is measured directly by the FADEC, using a resolver hardwired to and excited by the FADEC. Both FADEC channels have their own resolver input - on most Boeing aircraft it's a common resolver with two sets of electrically isolated windings, however on the 787 it actually uses two mechanically separate resolvers. The resolver is basically read as "sine" and "cosine" which is converted in the angle. This also makes error detection easy, using the sine squared + cosine squared relationship. Any other aircraft systems that use TLA use the TLA signal relayed back to the aircraft by the FADEC.
The fuel control switch is a two-position multiple pole 'latching' switch - you have to pull it out slightly over detent to move it between the RUN and CUTOFF positions (on other aircraft there is an interposing relay for some of the functions. not sure about the implementation on the 787). Moving the switch to cutoff sends a DC signal to both the High Pressure ShutOff Valve (HPSOV) in the fuel control and the spar valve commanding them to close. HPSOV is solenoid actuated and is near instantaneous, Spar Valve takes ~one second to change positions (yes, this is different than some other airframers that only send the signal to one valve or the other, but it's been standard Boeing design practice since the early 1970s). Both the HPSOV solenoid and the Spar Valve are designed to stay in their last commanded position if airframe power is lost. Moving the switch to CUTOFF also sends a 'reset' signal to the FADEC - meaning the FADEC will be offline for roughly one second. On the 787 (and 777 and 747-8), there is a brief pause (~0.25 seconds) before the shutdown signal is sent to the engine to allow the electrical system to reconfigure to prevent a brief interrupt of electrical power to the rest of the aircraft.
Pulling the Fire Handle does the same thing as the fuel condition switch - via separate wiring (physically isolated from the fuel switch wiring to help protect from things like rotor burst damage), with the exception of the FADEC reset (since there is no requirement to be able to restart the engine after a Fire Handle shutdown).
There is absolutely no TLA input into either the fuel conditions switch or the Fire Handle - you can shutdown the engine via either regardless of Thrust Lever Angle.
All this is standard Boeing design practice (and except for the no-break electrical power transfer) has been for at least 50 years. This is enforced by the Boeing "Design Requirements and Objectives" - DR&O - compliance with is demonstrated by an audit after the final design freeze.
July 11, 2025, 20:30:00 GMT
permalink Post: 11919765
From the Report:
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. The Engine N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cut off.
In the cockpit voice recording, one of the pilots is heard asking the other why did he cutoff.
The other pilot responded that he did not do so.
In the cockpit voice recording, one of the pilots is heard asking the other why did he cutoff.
The other pilot responded that he did not do so.
July 11, 2025, 20:40:00 GMT
permalink Post: 11919771
- fuel cut offs were found in the RUN position
- on take off roll both engines lost power as the fuel cut offs went from RUN to cutoff
- CVR recorded one pilot asking why they had gone to CUTOFF
- within 10 seconds the fuel cutoff was moved back to RUN
-RAT was deployed, APU had begun auto start
- 32 seconds after Vr the MAYDAY was called
This should also dispel a lot of the comments about AAIB-India, Indian culture in general and general competence. For a preliminary report this is far more thorough and extensive than what would normally be expected and they\x92ve kept Boeing, GE, FAA and investigators from US, UK, Canada and Portugal in the loop from the start
They have also clarified why it took so long to do the EAFR download- because of the extensive damage they had to source specialist equipment from the NTSB that only arrived on the 23rd of June (they downloaded on the 24th) so all that talk of a \x91coverup\x92 is pretty embarrassing now
of course the big question is why/how those switches were commanded into cutoff in the first place the exact sequence at Vr is the most critical, there hasn\x92t been much scrutiny at all that I can see in the Indian/international media of the personal
background of the flight deck crew which has happened in other suspected pilot initiated disasters in the past, I guess this is an avenue investigators will have been doing themselves
- on take off roll both engines lost power as the fuel cut offs went from RUN to cutoff
- CVR recorded one pilot asking why they had gone to CUTOFF
- within 10 seconds the fuel cutoff was moved back to RUN
-RAT was deployed, APU had begun auto start
- 32 seconds after Vr the MAYDAY was called
This should also dispel a lot of the comments about AAIB-India, Indian culture in general and general competence. For a preliminary report this is far more thorough and extensive than what would normally be expected and they\x92ve kept Boeing, GE, FAA and investigators from US, UK, Canada and Portugal in the loop from the start
They have also clarified why it took so long to do the EAFR download- because of the extensive damage they had to source specialist equipment from the NTSB that only arrived on the 23rd of June (they downloaded on the 24th) so all that talk of a \x91coverup\x92 is pretty embarrassing now
of course the big question is why/how those switches were commanded into cutoff in the first place the exact sequence at Vr is the most critical, there hasn\x92t been much scrutiny at all that I can see in the Indian/international media of the personal
background of the flight deck crew which has happened in other suspected pilot initiated disasters in the past, I guess this is an avenue investigators will have been doing themselves
July 11, 2025, 20:40:00 GMT
permalink Post: 11919772
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. The Engine N1
and N2 began to decrease from their take-off values as the fuel supply to the engines was cut
off.
In the cockpit voice recording, one of the pilots is heard asking the other why did he cutoff.
The other pilot responded that he did not do so.
The CCTV footage obtained from the airport showed Ram Air Turbine (RAT) getting deployed
during the initial climb immediately after lift-off (fig. 15). No significant bird activity is observed
in the vicinity of the flight path. The aircraft started to lose altitude before crossing the airport
perimeter wall.
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. When fuel control switches are moved from CUTOFF to
RUN while the aircraft is inflight, each engines full authority dual engine control (FADEC)
automatically manages a relight and thrust recovery sequence of ignition and fuel introduction.
The EGT was observed to be rising for both engines indicating relight. Engine 1’s core
deceleration stopped, reversed and started to progress to recovery. Engine 2 was able to
relight but could not arrest core speed deceleration and re-introduced fuel repeatedly to
increase core speed acceleration and recovery. The EAFR recording stopped at 08:09:11
UTC
As per the EAFR data both engines N2 values passed below minimum idle speed, and the
RAT hydraulic pump began supplying hydraulic power at about 08:08:47 UTC.
RAT in extended position
15
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. When fuel control switches are moved from CUTOFF to
RUN while the aircraft is inflight, each engines full authority dual engine control (FADEC)
automatically manages a relight and thrust recovery sequence of ignition and fuel introduction.
The EGT was observed to be rising for both engines indicating relight. Engine 1’s core
deceleration stopped, reversed and started to progress to recovery. Engine 2 was able to
relight but could not arrest core speed deceleration and re-introduced fuel repeatedly to
increase core speed acceleration and recovery. The EAFR recording stopped at 08:09:11
UTC
At about 08:09:05 UTC, one of the pilots transmitted “MAYDAY MAYDAY MAYDAY”.
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. The Engine N1
and N2 began to decrease from their take-off values as the fuel supply to the engines was cut
off.
In the cockpit voice recording, one of the pilots is heard asking the other why did he cutoff.
The other pilot responded that he did not do so.
The CCTV footage obtained from the airport showed Ram Air Turbine (RAT) getting deployed
during the initial climb immediately after lift-off (fig. 15). No significant bird activity is observed
in the vicinity of the flight path. The aircraft started to lose altitude before crossing the airport
perimeter wall.
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. When fuel control switches are moved from CUTOFF to
RUN while the aircraft is inflight, each engines full authority dual engine control (FADEC)
automatically manages a relight and thrust recovery sequence of ignition and fuel introduction.
The EGT was observed to be rising for both engines indicating relight. Engine 1’s core
deceleration stopped, reversed and started to progress to recovery. Engine 2 was able to
relight but could not arrest core speed deceleration and re-introduced fuel repeatedly to
increase core speed acceleration and recovery. The EAFR recording stopped at 08:09:11
UTC
As per the EAFR data both engines N2 values passed below minimum idle speed, and the
RAT hydraulic pump began supplying hydraulic power at about 08:08:47 UTC.
RAT in extended position
15
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. When fuel control switches are moved from CUTOFF to
RUN while the aircraft is inflight, each engines full authority dual engine control (FADEC)
automatically manages a relight and thrust recovery sequence of ignition and fuel introduction.
The EGT was observed to be rising for both engines indicating relight. Engine 1’s core
deceleration stopped, reversed and started to progress to recovery. Engine 2 was able to
relight but could not arrest core speed deceleration and re-introduced fuel repeatedly to
increase core speed acceleration and recovery. The EAFR recording stopped at 08:09:11
UTC
At about 08:09:05 UTC, one of the pilots transmitted “MAYDAY MAYDAY MAYDAY”.
08:08:42 Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position.
One of the pilots asks the other why did he cutoff.
The other pilot responded that he did not do so.
08:08:52 Engine 1 fuel cutoff switch transitioned from CUTOFF to RUN
08:08:56 Engine 2 fuel cutoff switch also transitions from CUTOFF to RUN
Who (or what?) operated the cutoff switches?
Last edited by Engineless; 11th July 2025 at 20:53 .
July 11, 2025, 20:46:00 GMT
permalink Post: 11919773
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?
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?
July 11, 2025, 20:57:00 GMT
permalink Post: 11919787
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?
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?
July 11, 2025, 21:07:00 GMT
permalink Post: 11919801
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'.
the cutoffs were found in the RUN position so there\x92s a lot more to this story
July 11, 2025, 21:12:00 GMT
permalink Post: 11919808
Yes, I can imagine that. My point was that the obstacle was there. But someone operated that switch clumsily at it got stuck on the edge. Just imagine that like I grab the switch, pull it out, move it up to the RUN but don't release it and keep it pulled out. Will it connect already at this moment or it has to be like in the down, not pulled out possition? Maybe the switches got stuck and fell down on its own. The question is, is that even possible?
July 11, 2025, 21:16:00 GMT
permalink Post: 11919815
"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, ..)
July 11, 2025, 21:24:00 GMT
permalink Post: 11919826
What the hell happened in the cockpit?
08:08:42 Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position.
One of the pilots asks the other why did he cutoff.
The other pilot responded that he did not do so.
08:08:52 Engine 1 fuel cutoff switch transitioned from CUTOFF to RUN
08:08:56 Engine 2 fuel cutoff switch also transitions from CUTOFF to RUN
Who (or what?) operated the cutoff switches?
08:08:42 Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position.
One of the pilots asks the other why did he cutoff.
The other pilot responded that he did not do so.
08:08:52 Engine 1 fuel cutoff switch transitioned from CUTOFF to RUN
08:08:56 Engine 2 fuel cutoff switch also transitions from CUTOFF to RUN
Who (or what?) operated the cutoff switches?
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.
July 11, 2025, 21:43:00 GMT
permalink Post: 11919847
What a puzzle.
If it was a deliberate act, why put them back to RUN?
IMO, it's unlikely the Pilot Flying (PF) moved the switches in error or deliberately. The PF has control of the aircraft at a low altitude.
Maybe the PNF just had a brain fart and just lied when confronted with the question, a very human response.
Why did it take 10 second to recognize the switches were in CUT OUT?
If it was a deliberate act, why put them back to RUN?
IMO, it's unlikely the Pilot Flying (PF) moved the switches in error or deliberately. The PF has control of the aircraft at a low altitude.
Maybe the PNF just had a brain fart and just lied when confronted with the question, a very human response.
Why did it take 10 second to recognize the switches were in CUT OUT?
July 11, 2025, 21:51:00 GMT
permalink Post: 11919857
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.
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.