Certified “plastic planes” have a conductive mesh embedded in the composite.
The various pieces are wired together, supposedly.
This is for both lightning protection (to conduct the huge current away from control linkages which might otherwise melt) and to preserve VHF comms and other nav signals (static wicks don’t make sense otherwise).
How is this dealt with in the homebuilt arena in the USA where these types can fly IFR, apparently without bonding? Is there some “magic” which makes it work?
Why should this problem be any worse for composite than for wood? Like a Robin DR 400? or any other wooden aircraft?
That’s a good question.
How is it solved on a wooden Robin (not all Robins are wood)?
(not all Robins are wood)
Perhaps that is the reason for explicitly mentioning the DR400.
As to the root of the matter: I’d not be surprised if wood, if not drier than the driest firewood, is conductive enough to avoid static build-up. Resistance in the order of Megaohms is sufficient, cfr. the “conductive” foam in which IC’s are sometimes shipped.
Yes – wood is probably going to be in the G-ohms range and thus slightly conductive, but if you are accumulating charge fast enough (as one would be flying in IMC) then it may not escape fast enough. Also you certainly can’t attach static wicks to wood, so do Robins not have these? Looking at one Lancair 320 that doesn’t have any wicks either so whatever works there is probably what also works with the Cirrus.
It takes very little arcing to kill VHF radio pretty effectively, as I found out when having a bit too much grease on the elevator bearings
But in IMC, humidity should be elevated, too? Doesn’t that help in getting rid of the static?
That aside, I was wondering if the Europa (or its US-certified cousin, but that one has aluminium wings, perhaps not accidentally) would not be a good illustration – anyone round who knows about its build?
On the plans for my wooden Turbulent there are bonding diagrams showing connections to every control surface or significant metal part. There’s a fair amount of aluminium in the covering (to block UV light) though as far as I’m aware it isn’t conductive.
I take it you mean there was mixed a fair amount of aluminium powder into the liquid chemicals that one spreads over the covering cloth, to taughten* it? People unacquainted with cloth covering might wonder… I think you are right that such powder changes little to electrical conductivity.
*(is that the right word? I could find nothing better)
Gliders of start of composite era did not have anything but internal static connection of metal parts. Sometimes the cabin was full of Elmos lightning es. If connected to earth by 1/4 mile long winch steel wire under TC cloud. Now most have some carbon fibre in construction so conductivity is guaranteed. In my composite propellor there is thin Al mesh under paint.
Agreed about wood aircraft as a baseline for the discussion. People have been flying IFR in Bellanca Vikings for roughly 50 years, and they were sold as a direct competitor to the Bonanza, as serious going places plane. They have a good safety record. Is it just a matter of most IFR operations in something like a Bellanca or composite homebuilt not being in weather conditions of concern? I find that a little hard to believe.