Originally Posted by
Uplinker
An airship I was once working in (but not piloting - during my television engineering years), had Porsche flat six engines driving the ducted fans. One of the engines had a persistent but intermittent slight misfire. The engineers eventually found that a coaxial cable which carried the ignition signal to that engine had somehow been wired wrong, so the earth was carried by the centre conductor and the signal by the outer screen. A coaxial cable is supposed to have the outer screen earthed so that the signal carried by the inner is screened against external interference.
As somebody has already suggested; one wonders if all the AoA probes on the grounded aircraft will be tested by hand : moving them back and forth, clockwise and anticlockwise by engineers through their whole range to see if there are any bad data spots or signal interruptions?
Thank you. Your post (and a few others) bring me back to something I added to the original Lion Air thread regarding what kind of tech support/field service support Boeing provides to its customers, and what is the cost? The kind of trouble shooting you refer to, and that I was pointing at, is often the kind of digging that a field service rep from the OEM is so good at, and why they exist.
Or did the LOCO airline (Lion Air) go cheap and not buy that? (Did Ethiopian Airlines have a field servicde package, and of what kind?)
The other issue of "why was the AoA cockpit thing an option rather than standard kit" has been done to death in the R&N thread, so I won't go there. The root problem, bad AoA signal getting to the electronic brain, has to be remedied down in detail from AoA probe to the connector at the flight computer.
GIGO.