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RomeoTangoFoxtrotMike
July 12, 2025, 20:04:00 GMT permalink Post: 11920795 |
See here
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. b79edb16af_5b3bb7a57d07fbf3c85529ab3f52308b609d82a3.png.webp Last edited by RomeoTangoFoxtrotMike; 12th July 2025 at 20:28 . |
Alty7x7
July 13, 2025, 00:08:00 GMT permalink Post: 11920951 |
Switch locking mechanism
I was just looking into these Honeywell TL family switches for a different project. There are certain part numbers that have the locking mechanism - the ones that don't are clearly different. I didn't see anything to indicate that the locking feature was selectable or defeatable. I suspect the faulty 737 switches fron 2018 had an issue with the detent machining or maybe the loading spring - i.e. a bad batch.
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EDML
July 13, 2025, 22:34:00 GMT permalink Post: 11921745 |
Two notes regarding the switches:
I pulled the Honeywell data sheet. It contains dozens of different versions of the same switch. There are locking / non locking / momentary press / 2 or 3 position versions all in the same data sheet. Furthermore they are waterproof:
The robust design of the TL Series toggle is well-suited for many military, aerospace and other demanding applications where reliability is essential. These applications include environments where the panels are subjected to mechanical shock, vibration, and temperature extremes as well as environments with dust, splashing or hose-directed water.
Here is the data sheet: https://www.mouser.de/datasheet/2/18..._1-1735572.pdf |
D Bru
July 15, 2025, 17:41:00 GMT permalink Post: 11923115 |
Hamster wheel diversification (at least an attempt): 787 core system hacking
Inspired by the mention in the
PR
about a MEL on the \x91core network\x92, I came across the polemics between Boeing and IOActive a few years ago about the alleged vulnerability of 787 core systems to outside interference (hacker attack from within a/c and/or ground), including the highly sensitive CDN module, from where also the fuel cut-off module can be accessed. It\x92s definitely not my specialty, but I thought to flag it in case someone has more informed ideas about this. To my mind it could potentially \x93outshine\x94 intentional crew action. Boeing at the time denied such options, of course. Obviously also in good faith, moreover it seems to be Honeywell &GE code anyhow, but who knows where we are 6 years on.
https://www.wired.com/story/boeing-7...ecurity-flaws/ Last edited by D Bru; 15th July 2025 at 18:10 . |
Lonewolf_50
July 15, 2025, 18:12:00 GMT permalink Post: 11923148 |
For Dr Bru and Engineless:
I think that there is a thread about hacking of airliners somewhere on PPRuNe, might want to take that discussion there. (Here is one, there are others) A short response to you both: 1. Note that the article was from 2019 2. I am very doubtful that this occurred, beyond estimating the efficacy of any protections Boeing and Honeywell will have come up with since that article was published. I doubt that either company sat on their hands after that Black Hat conference. 3. Caveat: yes, hackers never sleep . = So some kind of sabotage is supposedly done, you think? = (I'll put the speculation into the spoiler)
Spoiler
But I think that you are both grasping at straws, for a variety of reasons, among which are: 1. No evidence to date. 2. Nothing in the report (but then, it's a prelim report) 3. If that kind of thing was going on, I don't think that the report would appear to lean so hard toward the human factors piece. 4. Unless that is part of the deception plan! ![]() 5. Yeah, right, we are back to the Hollywood thriller that neither of you have gotten a producer to try and get filmed. 6. Fear 7. Surprise 8. A fanatical devotion to Saint Bernoulli. Please take any further discussion of this line of inquiry to a thread involving hacking. Thank you all in advance. T28B (As an aside: if you took a look at the debris field, and the fact of the post impact fire, finding any evidence of something like what you are alluding to would be tough unless there's a way to parse EAFR information to detect the intrusion into the system of spurious / outside signals). Last edited by T28B; 15th July 2025 at 19:52 . Reason: Alert to move hacking discussion elsewhere |
D Bru
July 15, 2025, 19:20:00 GMT permalink Post: 11923194 |
A short response to you both:
1. Note that the article was from 2019 2. I am very doubtful that this occurred, beyond estimating the efficacy of any protections Boeing and Honeywell will have come up with since that article was published. 3. Caveat: yes, hackers never sleep . But I think that you are both grasping at straws, for a variety of reasons…... |
EDML
July 15, 2025, 22:08:00 GMT permalink Post: 11923307 |
After all the analysis on PPRuNE, fuel switch failure (well, dual switch failure, at practically the same time) seems so unlikely it's no longer worthy of consideration. However, I'm still open to the idea of a failure elsewhere that may have signalled the fuel switches had transistioned from Run to Cutoff wthout physical movement of either switch. Why? Firstly, because of this (taken from the preliminary report)
Inspired by the mention in the
PR
about a MEL on the ‘core network’, I came across the polemics between Boeing and IOActive a few years ago about the alleged vulnerability of 787 core systems to outside interference (hacker attack from within a/c and/or ground), including the highly sensitive CDN module, from where also the fuel cut-off module can be accessed. It’s definitely not my specialty, but I thought to flag it in case someone has more informed ideas about this. To my mind it could potentially “outshine” intentional crew action. Boeing at the time denied such options, of course. Obviously also in good faith, moreover it seems to be Honeywell &GE code anyhow, but who knows where we are 6 years on.
https://www.wired.com/story/boeing-7...ecurity-flaws/ |
BrogulT
July 16, 2025, 22:20:00 GMT permalink Post: 11924037 |