Posts by user "EDML" [Posts: 48 Total up-votes: 0 Pages: 3]

Originally Posted by tdracer

... The fuel switch discrete doesn't really get used except for engine start - if it falsely indicates shutdown (on one or both channels), the FADEC won't do anything if the engine is already running. All this will set maintenance faults - and associated EICAS Status messages (L/R ENGINE CONTROL or ENGINE C1)...

Originally Posted by FullWings

...
We now know it is a HF accident, not an aeroplane technical one and although I would like to know exactly what happened, I’m much less concerned for the 787 and aviation in general, to the point that in this case I’ve lost a lot of interest in the eventual conclusion, if there ever is one.

Originally Posted by JustusW

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Which actually brings me to this one because I would like to ask for a bit of clarification: By "fuel switch discrete" are you referring to the Fuel Control Switches discussed in the preliminary report?
I would assume from your statement, that if a mismatch in the NC/NO signal on the switch was detected the FADEC would not direct the Fuel Cutoff Valves to close (as far as the types you are familiar with are concerned), is that correct?
...

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)

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/

Originally Posted by Feathers McGraw

Question for those that actually put together the 787 FC switches and the module into which they are attached.

How does the mounting nut fit over the illuminated part of the knob on the end? It looks too narrow to me. I'm assuming that the switch part with the knob and which might contain the spring is removable so that the lower part of the switch plus wiring is pushed through the panel from the underside and the securing nut and washer is then passed down over the threaded portion and tightened on to the panel. How does the top part of the switch with the illuminated knob then attach to the narrow cylindrical part of the switch poking through from below?

Originally Posted by tdracer

Something else that has been repeatedly discussed in the three threads...
While there are interposing relays, the signals to the Fuel Metering Unit shutoff valve and the Spar Valve are hardwired from the switches to the valves in question. They don't go through some computer interface that could corrupt the signals.

Originally Posted by Triskelle

An interesting quotation from this: "She highlighted a similar incident during which one of the engines suddenly shut down midflight on an All Nippon Airways Boeing 787 during its final approach to Osaka, Japan, in 2019.

Investigators later found that the aircraft’s software had mistakenly interpreted the plane as being on the ground, triggering the thrust control malfunction accommodation system, which automatically moved the fuel switch from “run” to “cutoff” without any action from the pilots."

Is it also interesting that this incident occurred at the time of ground-to-air transition?