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| LTC8K6
July 12, 2025, 22:55:00 GMT permalink Post: 11920905 |
I have not seen this question asked anywhere and I'm a software engineer (non-aviation), so felt I had to ask it:
Do these solid-looking mechanical fuel switches really act directly upon the fuel system or are they routed via the control system as logic (0/1) signals? It would certainly save a lot of copper and looming time to convert their output into a logic signal before it leaves the cockpit... If the former, ignore all that follows, as it is wrong. If the latter, a control software glitch or electrical noise/short could cause the fuel switches to appear to the control system as being briefly off, while the pilots see the physical switches are still in the on position. Even if such a noisy electrical signal rapidly reverted to correctly indicating fuel-switch on-state after even a few milliseconds, any control system might well have embarked upon a relatively slow relight/startup/engine-protection procedure. In such a scenario, the pilot who first noticed the engines spinning down would query it, while the other pilot would look at the physical switches and see that they were (still) on, and initially be non-plussed by the question. Need to ask the question now satisfied. Andy With that info, your scenario seems very unlikely. Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All) Fuel Cutoff Switches |
| LTC8K6
July 13, 2025, 12:38:00 GMT permalink Post: 11921293 |
I don't think it's yet time to go "there".
Remember that engine 1 had actually relit and began to recover and engine 2 had also relit. To me it's amazing that those big engines were able to do that in the time allotted. Why would a suicidal pilot even allow the attempt to restart within 10 seconds? Why wouldn't he yell out the other pilot's name and ask "What are you doing?" for the CVR theater performance? Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CVR Relight |
| LTC8K6
July 13, 2025, 20:44:00 GMT permalink Post: 11921633 |
I'm not sure it is amazing? All I read into the report's words is that the FCSs were turned on, I assume that this will see fuel flow to the combustion chambers and ignitors within 1s, and if the fuel ignites (why not?) EGT rises and the report records this as "relit".
The low airspeed airflow through engine and HP RPM on Eng 1 were sufficient to allow HP RPM to increase. The longer delay between Eng 2 OFF then ON allowed HP RPM to decay more than #1, and although 'relit', I read a successful (unassisted) spool up was unlikely? (i.e. a detailed unassisted relight envelope including current HP RPM and IAS would have #1 in the envelope and #2 outside). Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All) Relight |
| LTC8K6
July 14, 2025, 11:19:00 GMT permalink Post: 11922098 |
What would prevent a pilot from simply covering the camera lens? Or otherwise disabling the camera. It will have to be on a CB that can be pulled.
We would then have endless arguments over whether the camera conveniently failed at just the right moment or was disabled. Subjects: None |
| LTC8K6
July 14, 2025, 20:51:00 GMT permalink Post: 11922492 |
If you think everything is said...
Breaking News: On Jul 14th 2025 India's DGCA instructed airlines to check the fuel switches on the Boeing 787 and Boeing 737 aircraft as used by Air India Group, Indigo and Spicejet for possible disengagement of the fuel control switch locking feature according to the SAIB released by the FAA on Dec 17th 2018. The checks have to be completed by Jul 21st 2025. Source: Avherald.com Subjects (links are to this post in the relevant subject page so that this post can be seen in context): DGCA FAA Fuel (All) Fuel Cutoff Switches Special Airworthiness Information Bulletin |
| LTC8K6
July 14, 2025, 21:11:00 GMT permalink Post: 11922506 |
I'm still not clear on something, no surprise there.
If you are the PF and you are just after rotation, and for whatever reason, the fuel control switches transition to "CUTOFF", when and how do you notice this? Presumably your hands are on the yoke and you are looking very intently out the windshield. So, to me it seems unlikely that you saw whatever happened to the switches, however they moved. Do you get a warning indication that the switches have moved? If so, then that would be what I needed to know. You got a warning and therefore you looked right at the switches. If not, do you just notice that you have lost power? If that is the case, where do you look first? I presume it would be at the engine info gauges/displays. What I'm getting at is what priority is given to looking at the fuel cutoff switches in this situation? How long until you look at those switches as the possible cause of the engine problems? Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All) Fuel Cutoff Fuel Cutoff Switches RUN/CUTOFF |
| LTC8K6
July 14, 2025, 23:42:00 GMT permalink Post: 11922578 |
Okay, thanks to all who gave info on my question.
Subjects: None |
| LTC8K6
July 15, 2025, 03:52:00 GMT permalink Post: 11922641 |
Subjects: None |
| LTC8K6
July 16, 2025, 22:32:00 GMT permalink Post: 11924039 |
It may be interesting to consider why people might decide to commit suicide in a manner that they believe will never be known as suicide?
Subjects: None |
| LTC8K6
July 17, 2025, 16:04:00 GMT permalink Post: 11924491 |
Has anyone considered a grudge against doctors as being a factor?
Subjects: None |