Posts about: "Honeywell" [Posts: 28 Pages: 2]

RomeoTangoFoxtrotMike
July 12, 2025, 20:04:00 GMT
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Post: 11920795
See here
Originally Posted by DTA
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
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Post: 11920951
Switch locking mechanism

Originally Posted by AlexGG
Could be installed with a locking mechanism disengaged.

I don't see in the report that the switches were in fact installed with the locking mechanism disengaged. Maybe I have missed it.
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.
EDML
July 13, 2025, 22:34:00 GMT
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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.
They are protected from hose-directed water. They could easily withstand a cup of coffee or even a whole bottle of 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
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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
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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
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Post: 11923194
Originally Posted by Lonewolf_50
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…...
Thanks really Lonewolf, I’m for sure not grasping at anything, let alone straws, just testing the sentiments on this one, which (unless I missed something) wasn’t subjected to the hamster wheel as yet, unlike imo far unlikely speculations
EDML
July 15, 2025, 22:08:00 GMT
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Post: 11923307
Originally Posted by Engineless
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)
There would have been multiple similar failures in different locations. The data for the EAFR is completely separated from the wiring and circuitry for the HP fuel valves. - And that on both engines.

Originally Posted by D Bru
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/
That is nonsense. There is no "fuel cut-off module". The fuel cut-off HP valves are operated directly by the cut-off switches through simple latching solenoids. No computer involved, not part of any communication network of the plane. The FADECs (which itself are totally separated from the rest of the aircraft) only get information on the status of the switches; e.g. to faciliate engine restart.
BrogulT
July 16, 2025, 22:20:00 GMT
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Post: 11924037
Originally Posted by fgrieu
What type of switches are they: SPST, SPDT with 3 wires used ? For SPST or equivalent, is "cutoff" the "make" or "break" state ?
Is there a common connection for the two switches, like a ground return or common live?
From earlier and from the Honeywell datasheet these are 4PDT switches with all 4 section having the center as a common (ground AFAIK ) so that the FDR and other circuits can positively see that the switch is on one condition or the other--except for the brief time that both are open during switching. Snap toggles like this are most commonly break-before-make as tdracer confirms (but 50ms seems like a long time...). What this means practically is that a break or short in the wiring would cause a fault that would be recognized as such since a correctly operating circuit will have one or the other but not both of the circuits completed and there are 4 sets of circuits.