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

Pilot DAR
July 12, 2025, 00:50:00 GMT
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Post: 11920045
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
If I recall correctly, the Mayday call was wording to the effect "thrust not achieved". That sounds like a phrase which could be expected from a pilot who had just frantically tried to restart an engine, and realized that it was not a success, and there would not be an opportunity for another attempt. The pilot aviated, (forget navigation), then communicated - over a period of 13 seconds.

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MLHeliwrench
July 12, 2025, 01:14:00 GMT
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Post: 11920059
Are you sure about that?

Is it time for a \x91are you sure about that?\x92 Prompt for select serious config changes?

My computer asks me that when clicking \x91delete\x92 on a file.

the way everything is integrated now - the airplanes are pretty good at knowing what\x92s \x92normal\x92

selecting cutoff on the engines while in ground mode could be considered normal, but while flying it could sure use a second verifying prompt.

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cooperplace
July 12, 2025, 01:15:00 GMT
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Post: 11920061
Originally Posted by The Brigadier
That \x93I didn\x92t\x94 on the CVR doesn\x92t sit right. If the cutoff switch movement was accidental, one would expect shock, confusion, or immediate troubleshooting, not a flat denial.
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.

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nomess
July 12, 2025, 01:25:00 GMT
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Post: 11920067
Originally Posted by MLHeliwrench
selecting cutoff on the engines while in ground mode could be considered normal, but while flying it could sure use a second verifying prompt.
The prompt is me sitting next to said persons cutting the switch saying \x91what the heck are you doing\x92.

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Loose rivets
July 12, 2025, 01:26:00 GMT
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Post: 11920068
I'm bewildered by the descriptions of the toggle switches. 'Lifting' is not the terminology I've lived with. The knob is pulled out so that the detents in the inner end of the knob can move over the sharp ridges on the switch body. A minor point, but what is not so minor is the inference that these detents and ridges are a safety design that is sometimes not installed. Surely, they must be talking about some further mechanism, or am I in the twilight zone? I cannot believe there's an aircraft with simple smooth action between off and on, an over-centre toggle . . . that will stop the engines!

The DC3 had fuel levers, the right two of six on the pedestal. We had to put our hand across the slots when selecting the mixture, so that our other hand wouldn't pull the lever to cut out. 60 years later there's a toggle that can be jogged to off?!

I'm not ready to accept the time-line. My FO's were not as highly trained and the aircraft much simpler, but I'd track what they were doing every second until I'd got comfortable airspace under me. Reaching out and stopping the engines? Asking why? What world are they living in?
WTFH!!!!!? followed by the switches being back on. I really don't think I was that much different to my colleagues - they'd darn soon react to fairly modest mistakes, let alone chopping the fuel.

I know the language and basic quotes are not necessarily as written, and trying to take into account the surreal predicament the 'other' pilot found himself in, but what I'm reading doesn't set the scene for an experienced skipper that's also a trainer being the one that's surprised by his colleagues action.

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appruser
July 12, 2025, 01:28:00 GMT
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Post: 11920070
Can someone with the engineering knowledge build a timeline/timeframe for fuel cutoff switch RUN to CUTOFF -> fuel stops -> engine flameout -> N2 drops to ? -> VFSGs quit -> RAT deployment starts -> RAT full power -> APU deployment start?
Does the RAT really start providing power in 4 seconds from the E2 fuel cutoff switch RUN -> CUTOFF?


Timeline from AAIB and the public CCTV video:

08:08:33 v1 153 kts
.
08:08:35 vr 155 kts
.
.
.
08:08:39 Liftoff, A/G Air Mode, rotation at 00:18 in public CCTV video
.
.
08:08:42 E1 Fuel Cutoff Switch RUN -> CUTOFF, 180 kts
08:08:43 E2 Fuel Cutoff Switch RUN -> CUTOFF
.............? N1 N2 begin to decrease
.............? "Why did you cutoff", "I didn't"
.............? Airport CCTV shows RAT
.............? N2 < idle speed
08:08:47 RAT hydraulic power
.
08:08:49 Public CCTV video: visible loss of thrust, Alt < 200ft using wingspan
.
.
08:08:52 E1 Fuel Cutoff Switch CUTOFF -> RUN, CCTV video: visible descent
.
08:08:54 APU inlet door begins opening
.
08:08:56 E2 Fuel Cutoff Switch CUTOFF -> RUN
08:09:05 MAYDAY
08:09:11 EAFR Recording stops
08:14:44 Crash Fire Tender leaves airport

Last edited by appruser; 12th July 2025 at 01:29 . Reason: readability

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Chiefttp
July 12, 2025, 01:43:00 GMT
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Post: 11920080
My only question is, after close to 40 years flying, on takeoff, if I lost thrust/ Power, my immediate reaction would NOT BE TO CHECK THE FUEL CONTROL SWITCHES. Unless the Pilot flying saw the Pilot monitoring visually reach down and shut the fuel control switches off, which would be odd since as the PF, your attention is looking at the instruments and outside, not inside and downward in the direction of the FC switches. It seems odd how quickly they ascertained the fuel control switches were shut off. No startle factor, or confusion, just a very quick determination that the FC switches were cutoff. Very strange.

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Pilot DAR
July 12, 2025, 01:43:00 GMT
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Post: 11920081
What happened before this to cause the engines to run down, resulting in the crew trying the documented procedure of turning the switches off then on to restart ?
Nothing in the report suggests that the engines began to run down before the fuel was selected to cutoff. The report states a sequence of events for power loss which begins with the switches being moved to cutoff. The maximum airspeed was immediately before the switches were moved, so there had not been a power rundown prior to that:

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.


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Someone Somewhere
July 12, 2025, 01:47:00 GMT
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Post: 11920083
Spoiler
 
Originally Posted by Finalveridict
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’re just getting casual comments about what the pilot allegedly said. Critical information—like the timing of transmissions, the checklist items completed before takeoff, and other key details that should be on the CVR—are 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.
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)

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jimtx
July 12, 2025, 01:51:00 GMT
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Post: 11920086
Originally Posted by Pilot DAR
Nothing in the report suggests that the engines began to run down before the fuel was selected to cutoff. The report states a sequence of events for power loss which begins with the switches MOVING or BEING MOVED to cutoff. The maximum airspeed was immediately before the switches were moved, so there had not been a power rundown prior to that:
Interesting that the report mentions SAIB No. NM-18-33. Can you see a detent on the left switch base in the mishap photo on page 10., Fig. 13? Yes kind of blurry when blown up but maybe we have some photo gurus.

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dmba
July 12, 2025, 01:53:00 GMT
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Post: 11920087
Originally Posted by zero/zero
Anyone who has flown the 777/787 (imagine the 737 is similar) probably recognises that the movement of those switches has a very easily identifiable audio signature.

Given the sensitivity of the CVRs, I would imagine it would be a very simple task in the full report to compare that to the unlikely scenario of the switches being in some halfway house and slipping to cut-off to to rotation or g-forces etc
Transitioning from Off to Run do the control switches require a similar lift and move mechanism?

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13 others
July 12, 2025, 01:55:00 GMT
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Post: 11920088
Originally Posted by Loose rivets
I'm bewildered by the descriptions of the toggle switches. 'Lifting' is not the terminology I've lived with. The knob is pulled out so that the detents in the inner end of the knob can move over the sharp ridges on the switch body. A minor point, but what is not so minor is the inference that these detents and ridges are a safety design that is sometimes not installed. Surely, they must be talking about some further mechanism, or am I in the twilight zone? I cannot believe there's an aircraft with simple smooth action between off and on, an over-centre toggle . . . that will stop the engines!
The Service Bulletin (link below) referenced on page 6 of the preliminary report describes just that...fuel control switches without detents or what the bulletin describes as a "locking feature" that can be "disengaged" and still allow the switch to function. It's somewhat of a glaring omission that the report did not state the status (detent or not) of the switches on this aircraft. Presumably if no-detent switches were found then an emergency AD would already have been issued.

https://ad.easa.europa.eu/blob/NM-18...SIB_NM-18-33_1

Last edited by 13 others; 12th July 2025 at 02:46 . Reason: spelling

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LTC8K6
July 12, 2025, 02:02:00 GMT
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Post: 11920092
Originally Posted by 13 others
The Service Bulletin (link below) referenced on page 6 of the preliminary report describes just that...fuel control switches without detents or what the bulletin describes as a "locking feature" that can be "disengaged" and still allow the switch to function. It's somewhat of a glaring omission that the report did not state the status (detent or not) of the switches on this aircraft. Presumably if no-detend switches were found then an emergency AD would already have been issued.

https://ad.easa.europa.eu/blob/NM-18...SIB_NM-18-33_1
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.

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Someone Somewhere
July 12, 2025, 02:02:00 GMT
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Post: 11920093
Consider this post with a picture of the switches in question:


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

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.

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.

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GXER
July 12, 2025, 02:39:00 GMT
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Post: 11920112
Originally Posted by Engineless
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?
I haven\x92t seen this question asked and answered so apologies if I\x92ve missed it.

What observation(s) would or could have alerted either pilot to the fact that the fuel cutoff switches had been set to CUTOFF?

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DahlHouse
July 12, 2025, 02:41:00 GMT
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Post: 11920113
Originally Posted by GXER
I haven\x92t seen this question asked and answered so apologies if I\x92ve missed it.

What observation(s) would or could have alerted either pilot to the fact that the fuel cutoff switches had been set to CUTOFF?
There is an EICAS message that comes up when an engine is shutdown (there is a small delay), which might prompt them to look at the switch - or just the sound the switch makes could prompt a quick glance down at the switch.

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jimtx
July 12, 2025, 02:41:00 GMT
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Post: 11920114
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.
I think they know. Page 10 Fig. 13. It's telling that they referenced the SAIB in the report.

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Tobin
July 12, 2025, 02:48:00 GMT
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Post: 11920120
Originally Posted by EDLB
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.
Originally Posted by Loose rivets
I'm not ready to accept the time-line. My FO's were not as highly trained and the aircraft much simpler, but I'd track what they were doing every second until I'd got comfortable airspace under me. Reaching out and stopping the engines? Asking why? What world are they living in?
WTFH!!!!!? followed by the switches being back on. I really don't think I was that much different to my colleagues - they'd darn soon react to fairly modest mistakes, let alone chopping the fuel.
Both of the comments above imply that the 10 second wait to set the switches back to RUN is excessive and inexplicable for an "experienced" pilot.

Having read both previous threads, I recall there were easily a dozen or two comments that claimed that a pilot's hands should be nowhere near the thrust levers or fuel switches until 400' AGL, no matter if an engine is out or on fire. (This was in response to suspicions that one of the pilots has prematurely actioned the engine-out memory items.) A similar number of comments emphasized that the pilots should calmly verify any engine-related issues before taking any action that might affect thrust, and that their training emphasizes this.

You can't have it both ways. Either pilots are expected to react instantly (and cause mistakes like shutting off both engines by misreading the situation) or they're expected to take a moment to assess an unexpected failure before acting (in which case 10 seconds is still pretty darn fast).

I lean toward the latter of those.






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Propjet88
July 12, 2025, 02:53:00 GMT
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Post: 11920122
I don’t 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’s assume that the switches were actually moved, and ignoring the “bad faith” 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’t 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, “muscle memory” (cerebellum activation if you prefer) may have taken the Captain’s 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’t 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 call.

Perhaps a bit of a stretch but not as much of a stretch as many of the other scenarios in this thread. I think it is a real possibility. Sadly, the only other explanation that I can see is the deliberate “bad faith” scenario, which we would all hope is incorrect.

Fly Safe
PJ88

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tdracer
July 12, 2025, 02:55:00 GMT
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Post: 11920123
Originally Posted by Tobin
Both of the comments above imply that the 10 second wait to set the switches back to RUN is excessive and inexplicable for an "experienced" pilot.
Ever since the two 767 events in the mid 1980's where a pilot - thinking he was activating the supervisory Electronic Engine Control switches - set both engine fuel switches to CUTOFF (fortunately at ~3,000 ft. so the engines had time to relight and recover), the FAA has mandated something called a "Quick Windmill Relight" capability. Basically - with the engine at high power - the fuel switch is set to CUTOFF, then (IIRC) ten seconds later set back to RUN. The engine must recover and produce thrust within (again, IIRC) 90 seconds. It's a very challenging test for the FADEC s/w.
I assume the 10 second pause is based on how long it took the two 767 event pilots to realize their error and return the switches to RUN.

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