" jls" wrote in news:%9_Mh.30455$sC.5421
@bignews2.bellsouth.net:


"Drew Dalgleish" wrote in message
[...]
I find it very hard to believe that forces strong enough to crack
4130
wouldn't be strong enough to crack powder coating.
I suspect the real reason for not powdercoating the chopper frame
has
a lot to do with filming schedules.

Whatever the reason for the FAA hostility for powder coating, I have
receive pma'd parts that were powdercoated, or "powercoated" as a
member of my EAA chapter calls it.

I believe the reason is that the coating can lift if the surface
underneath gets a bit rusty, forming a pocket where moisture can form
between the coating and the steel. The coating won't deform and flake
off in the same way that paint will and the rust will continue until
it's eaten through something with little or no external evidence that
that is happening. There have been some real problems with tube
airplanes in wet regions and in fact the UK CAA is considering banning
it altogether.


ALC