KR> Re: Exfoliation and trim tabs

[Larry H.]

Several years ago it was discovered on VariEzes that the aluminum wing attach 
fittings had corrosion like this and some of the aluminum canard elevator 
torque 
tubes in Longezes and Variezes had a corrosion problem. The highly recommended 
solution was to have these aluminum parts anodized before installation to help 
prevent this problem.
Take note that most of the problems were with airplanes that had been built and 
spent most of their lives in coastal places like Florida, near sea shores where 
salty air can be a problem for aluminum and especially aluminum airplanes.
Ever since I have been in the airplane owning game, all the old guys that 
taught 
me always warned me to not purchase any airplanes that had spent time in 
coastal 
areas. Might be an old wives tale but it makes sense to me so I have always 
followed that advice.
Larry Howell

KR> Re: Exfoliation

[smwood]

Air, Water and Light: Essential elements of life for mere mortals.
Air, Water and Light: Essential elements of destruction for aluminum, steel, 
epoxy, paint and just about any other mortal-made object.
Moral of the story: Coat every surface, including bolt holes, to keep air 
off.  Keep everything dry.  Keep epoxy in the dark.
Easy to say; lot of effort to do.

Sid Wood
Tri-gear KR-2 N6242
Mechanicsville, MD, USA
smw...@md.metrocast.net

--

Just a heads up really for anyone on the list flying an older KR2 ... I have
a recently imported 30 yr old aircraft and had a condition report done on
Friday. This is where a qualified aircraft engineer comes to have a look as
part of the re registration process .

He found three instances of exfoliation corrosion, two on the flap
attachments at the base of the fuselage (one on each side) and one on the
elevator trim horn.

Although I hadn't seen the flap attachment brackets, when It was pointed out
to me, it was obvious, with the aluminium crush plate peeled open in layers,
the layers pinched together by the bolts ..

The scary one was the trim cable attachment. This just looked like a
slightly rusty clevis on the cable. The corrosion on the horn was mostly
hidden. Once I had dismantled the connection, I gently scraped the control
horn with a screw driver, and the aluminium just peeled back in layers under
where the clevis had been sitting and, in the line of the cable, the
material just crumbled away leaving the pin (if it had still been in place)
free to pull out!  There are a couple of pictures of the elevator horn here
...
http://www.recreationalflying.net/showthread.php/141493-How-an-L2-saved-my-l
ife-. 

Regards

Martin