Originally Posted by
SASless
Reading the Report it appears to me that the affected control tube is not metallic....am I right in that?
If so...had it been of metallic construction would that Tube have been damaged as it was?
Also I feel I was asking the right question when early on I posed this question.....
The Control Tube was not severed but was compromised to the extent that the flight controls were damaged badly enough to greatly compromise their effectiveness.
Two very rare and apparently unrelated problems happening at the same time is more than mere coincidence.
The good news is now we have a full understanding of what caused the problems and the relevant questions may begin to be answered as to how to prevent a recurrence can begin.
The joys of CFRP in modern aircraft and unintended consequences! Most people understand CFRP as just "fancy fibreglass" and a composite material but forget or do not realise that Carbon Fibre conducts electricity quite well. When you get a large current flowing through it the filaments get hot, unlike a metal component that might melt locally at the contact point and break the short circuit. Whether it would have made a difference here is questionable.
The cable in question would have got the full output of GEN 1 by the looks i.e. 300 Amps or better. Certainly would have been a significant "whoof"!
The more "electric" aircraft get means a lot more respect to electrical components needs to be paid as the consequences can go a lot further than expected. Seems the issue was QC at manufacture?
Know of a machine that had aftermarket combined nav light / strobes fitted. Short between high voltage strobe wire and nav light wiring blew out both collective LVDT's and FADECs reset to a nominal Nr which was substantially lower than normal. Turned out that in one of the overhead panel connectors the nearest pin to the NAV wiring was part of the FADEC circuit!
There are also issues with bonding of CFRP with regard to lightning strike. You need a low resistance path to dissipate the energy and not cause high resistance and subsequent heating which can possibly cause the structure to fail. Hence CFRP structures normally have a copper mesh embedded in the surface of the structure. Being electrically conductive also brings up the issue of galvanic corrosion and dissimilar materials. I have seen some ugly stuff where CFRP, its copper mesh are other alloy structures need to be bonded. Al alloy and copper? WTF?