July 11, 2025, 21:54:00 GMT
permalink Post: 11919862
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?
I would have thought a pilot would notice the engines spooling down, and comment on that. To immediately jump to the cutoff switches as the cause rather implies something drew attention to the switches.
Then there is a 10+ second gap before the switches are set to run again. I can't think of any good reason why the PNF would have taken so long to correct an accidental or deliberate manipulation of the switches.
July 11, 2025, 21:55:00 GMT
permalink Post: 11919864
One item in the report is the position of the LG Lever - Down.
Given the lack of a full transcript, and in trying to defend the crewmembers intentions , Is it possible that at the point of "Positive Rate - Gear Up" - PM Brain farted, and performed a different muscle memory action? Thus they would deny moving the Switches - and take a few seconds to compute what they just did?
Given the lack of a full transcript, and in trying to defend the crewmembers intentions , Is it possible that at the point of "Positive Rate - Gear Up" - PM Brain farted, and performed a different muscle memory action? Thus they would deny moving the Switches - and take a few seconds to compute what they just did?
July 11, 2025, 21:57:00 GMT
permalink Post: 11919867
It can only know their electrical, not mechanical positions. Think about it, how would that work?
Would love to see some kind of accelerometer reading of the moment the switches went to cut off. Or even cockpit area audio.
They will figure it out.
Would love to see some kind of accelerometer reading of the moment the switches went to cut off. Or even cockpit area audio.
They will figure it out.
July 11, 2025, 22:00:00 GMT
permalink Post: 11919868
Agreed, it's most unfortunate that that the preliminary report hasn\x92t 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\x92s so neutered, "Why did you cut off?\x94 / \x93I didn\x92t\x94, that it raises more questions than it answers. If the goal was to reassure or clarify, it\x92s had the opposite effect.
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\x92s so neutered, "Why did you cut off?\x94 / \x93I didn\x92t\x94, that it raises more questions than it answers. If the goal was to reassure or clarify, it\x92s had the opposite effect.
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.
July 11, 2025, 22:04:00 GMT
permalink Post: 11919872
The landing gear lever is forward and up on the centre instrument panel, adjacent to the PFD. The two fuel control switches are aft and low, on the thrust pedestal. There's no reasonable way to confuse one for the other in terms of position, hand movement or 'muscle memory'.
July 11, 2025, 22:04:00 GMT
permalink Post: 11919873
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.
July 11, 2025, 22:04:00 GMT
permalink Post: 11919874
The landing gear lever is forward and up on the centre instrument panel, adjacent to the PFD. The fuel control switches are aft and low, on the thrust pedestal. There's no reasonable way to confuse one for the other in terms of position, hand movement or 'muscle memory'.
July 11, 2025, 22:04:00 GMT
permalink Post: 11919875
Actually, why are switches that are only really required on the ground or in an engine shut down event where they are? Embraer's have the switches out of the way on an overhead panel and as well as detent locked, have a protective guard, one has to physically lift. If the PF had to physically carry out the engine shut down on an Embraer, he would have to raise his arm. Would be obvious to the PnF.
July 11, 2025, 22:05:00 GMT
permalink Post: 11919876
The landing gear lever is forward and up on the centre instrument panel, adjacent to the PFD. The two fuel control switches are aft and low, on the thrust pedestal. There's no reasonable way to confuse one for the other in terms of position, hand movement or 'muscle memory'.
July 11, 2025, 22:06:00 GMT
permalink Post: 11919877
In the case of (2) or (3), would the expected response be "Why did you cutoff"?
I would have thought a pilot would notice the engines spooling down, and comment on that. To immediately jump to the cutoff switches as the cause rather implies something drew attention to the switches.
Then there is a 10+ second gap before the switches are set to run again. I can't think of any good reason why the PNF would have taken so long to correct an accidental or deliberate manipulation of the switches.
I would have thought a pilot would notice the engines spooling down, and comment on that. To immediately jump to the cutoff switches as the cause rather implies something drew attention to the switches.
Then there is a 10+ second gap before the switches are set to run again. I can't think of any good reason why the PNF would have taken so long to correct an accidental or deliberate manipulation of the switches.
You need to take the audio together with the switch data, not in isolation.
The two combined would appear to rule out a lot of options that the data alone would leave possible.
July 11, 2025, 22:06:00 GMT
permalink Post: 11919878
Out of interest, hypothetically if the captain was an instructor, is there a possibility that any kind of muscle memory from simulated failures in the simulator may have been triggered?
Let\x92s say that you are having to retrain another pilot on v1 cut handling whilst you occupy the P1 seat. Temptation may be to use the fuel cut off switches to save time rather than going back to the sim operator panel to reprogram the failure.
Let\x92s say that you are having to retrain another pilot on v1 cut handling whilst you occupy the P1 seat. Temptation may be to use the fuel cut off switches to save time rather than going back to the sim operator panel to reprogram the failure.
July 11, 2025, 22:07:00 GMT
permalink Post: 11919881
A douple-pole switch. One pole used for FDR signal for the physcial switch position. The other pole for the electrical switching circuit.
July 11, 2025, 22:08:00 GMT
permalink Post: 11919884
I know it's not a popular opinion around here but it seems like a flight deck camera would be quite useful right about now to determine whether either pilot's hands strayed near the fuel cutoff switches at the recorded time.
July 11, 2025, 22:09:00 GMT
permalink Post: 11919886
Seconds count:
Time was spent with the verbal exchange, and then perhaps each pilot expected the other to put the switch back?
Anyway, the preliminary report also establishes that the aircraft had only 3-4 seconds of powered flight. (Would the gear lever be operated that early?) Everyone who saw that from the CCTV video, pat yourselves on the back.
Mayday call, dual engine failure, RAT deployment all confirmed.
TCMA was a red herring, the aircraft was firmly in air mode as the accident unfolded, and the thrust levers were at takeoff thrust the whole time.
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.
That was with 10 seconds delay vs. 13 seconds for engine 2.
Time was spent with the verbal exchange, and then perhaps each pilot expected the other to put the switch back?
Anyway, the preliminary report also establishes that the aircraft had only 3-4 seconds of powered flight. (Would the gear lever be operated that early?) Everyone who saw that from the CCTV video, pat yourselves on the back.
Mayday call, dual engine failure, RAT deployment all confirmed.
TCMA was a red herring, the aircraft was firmly in air mode as the accident unfolded, and the thrust levers were at takeoff thrust the whole time.
July 11, 2025, 22:12:00 GMT
permalink Post: 11919889
Spoiler
I wouldn't put too much significance in the "01 second" since this still is close enough for an unintentional cause.
No matter what: The design and position of the fuel cut off switches is potentially prone for mishaps.
July 11, 2025, 22:12:00 GMT
permalink Post: 11919891
Folks, it appears that the message isn't getting through.
There were two professional pilots on that flight deck.
It is not acceptable to effectively accuse both of a criminal act, because there is no evidence to identify which hand - if either - moved the fuel switches, or for what purpose or reason.
Unless and until any such evidence is published by the relevant authorities, kindly desist from doing so out of respect for your professional colleagues.
There were two professional pilots on that flight deck.
It is not acceptable to effectively accuse both of a criminal act, because there is no evidence to identify which hand - if either - moved the fuel switches, or for what purpose or reason.
Unless and until any such evidence is published by the relevant authorities, kindly desist from doing so out of respect for your professional colleagues.
July 11, 2025, 22:13:00 GMT
permalink Post: 11919892
There are two options. The fuel cut off was accidental or it was deliberate. The question from one of the pilots is why did you do that? The other pilot denied it.
The fuel was cut off but restored too late.
The 'why did you do that' question is significant. It wasn't 'What happened?' or 'How did that happen'
Of course it could have happened accidentally. 757 pilots might have input.
The fuel was cut off but restored too late.
The 'why did you do that' question is significant. It wasn't 'What happened?' or 'How did that happen'
Of course it could have happened accidentally. 757 pilots might have input.
July 11, 2025, 22:15:00 GMT
permalink Post: 11919893
For those sky gods who confidently state they would reset the cutoff switches immediately I would say that 10 seconds is not a particularly unusual time for startle effect to impair cognition, especially for something as monumental and unexpected as a dual engine failure at rotation. One reference amongst many:
https://www.icao.int/Meetings/LOCI/P...Strategies.pdf
And for those who scoff at the possibility of the PM inadvertently operating the cutoff switches (which is done as frequently as operating the gear lever), I\x92d remind you that more than one Airbus has landed with its parking brake on after the PM inadvertently set it rather than arming the spoilers.
And for those who scoff at the possibility of the PM inadvertently operating the cutoff switches (which is done as frequently as operating the gear lever), I\x92d remind you that more than one Airbus has landed with its parking brake on after the PM inadvertently set it rather than arming the spoilers.
July 11, 2025, 22:16:00 GMT
permalink Post: 11919894
From the report, there is no indicated time stamp identifying the point when one pilot asked the other "why did you cut off"
This could explain the the assumption that it took ten seconds to reverse the switch positions.
Cut off could have been noticed at any point later than 08:08:42 but before 08:08:52.
This could explain the the assumption that it took ten seconds to reverse the switch positions.
Cut off could have been noticed at any point later than 08:08:42 but before 08:08:52.
July 11, 2025, 22:17:00 GMT
permalink Post: 11919895
Background
The Boeing Company (Boeing) received reports from operators of Model 737 airplanes that the fuel control switches were installed with the locking feature disengaged. The fuel control switches (or engine start switches) are installed on the control stand in the flight deck and used by the pilot to supply or cutoff fuel to the engines. The fuel control switch has a locking feature to prevent inadvertent operation that could result in unintended switch movement between the fuel supply and fuel cutoff positions. In order to move the switch from one position to the other under the condition where the locking feature is engaged, it is necessary for the pilot to lift the switch up while transitioning the switch position. 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. Inadvertent operation of the switch could result in an unintended consequence, such as an in-flight engine shutdown.
...The table below identifies the affected airplane models and related part numbers (P/Ns) of the fuel control switch, which is manufactured by Honeywell.
...787-8, -9, and -10
The Boeing Company (Boeing) received reports from operators of Model 737 airplanes that the fuel control switches were installed with the locking feature disengaged. The fuel control switches (or engine start switches) are installed on the control stand in the flight deck and used by the pilot to supply or cutoff fuel to the engines. The fuel control switch has a locking feature to prevent inadvertent operation that could result in unintended switch movement between the fuel supply and fuel cutoff positions. In order to move the switch from one position to the other under the condition where the locking feature is engaged, it is necessary for the pilot to lift the switch up while transitioning the switch position. 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. Inadvertent operation of the switch could result in an unintended consequence, such as an in-flight engine shutdown.
...The table below identifies the affected airplane models and related part numbers (P/Ns) of the fuel control switch, which is manufactured by Honeywell.
...787-8, -9, and -10
Last edited by 13 others; 12th July 2025 at 01:40 . Reason: Bold emphasis mine, fixed link