Originally Posted by
Snyggapa
Not what the leak above suggests, which implies that I guess a permanent live for another part of the system runs in close proximity to the stab trim after the cutout switch - so if the two chafe and short, you get an uncontrolled runaway that you can't stop.
"In one instance, engineers found a hot power wire that was too close to two command wires running to the jet’s moveable horizontal tail, or stabilizer, one for commanding the tail to swivel to move the jet nose-up, the other to move it nose-down. The danger is a short that causes arcing of electricity from the hot wire to the command wire.
“If a hot short occurs between the power wire and either the up or down command wire, the stabilizer can go to the full nose-up or nose-down position,” the engineer said.
Furthermore, the electrical power in that wire could circumvent the cutoff switches in the cockpit that, in the event of such a stabilizer runaway, are used to kill electrical power to the tail. Theoretically, the pilots could be unable to shut it off."
That's a fairly untidy situation. Applying opposite trim would have power to both sides of the trim motor, would be interesting to see how the logic circuits would work with that. TBC would be able to identify the potential power source for the offending wiring, and ascertain if they can be isolated safely without shedding power down to a dark plane. The plane can fly dark, not much fun and not great for pax experience, but it ain't necessarily over until the singing is done. (Take an iPad, Stratus S2, and an iridium go.... and Amex card, don't leave home without them)
[Off topic slightly, but FYI the following show what is available as information available from a completely independent system on an aircraft. That is 1090 ADSB IN info and a synthetic view of traffic, terrain, runway etc having spent 1/2 a million on "modern" systems, in the last couple of years, the only system that really impresses me is that below. No iPad, no fly IMHO. The iPad gives better information than TCAS II Ch 7.1 for my money. Add to the fact it uploads FPL to the APFD's, and we can modify the current path from the iPad, it's pretty neat. The SA enhancement is impressive in high terrain areas, better than the dual TAWS EGPWS/GPWS system for SA]
