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VARI-EZE MAIN WING ATTACH - CORROSIONFrom CP55, Page 5 (April, 1988)
Since we first reported the
corrosion problem in VariEze main wing attach plates in CP53, page 7, we have heard
from only two or three builder/flyers who had found signs of corrosion. Just this
week, we received a letter from a VariEze owner/pilot who found corrosion in the WA-2-2
plate. He has spent a considerable amount of time and energy removing this plate, in fact,
he said he almost resorted to using dynamite! He sent us the WA-2-2 plate, the lower plate
of the top two plates mounted to the centersection spar. By far the toughest plate to
remove and replace. This plate (see photo) has one of the worst cases of intergranular
corrosion we have seen. It is absolutely not safe to fly and must be replaced.
Unfortunately, this is probably going to be very difficult, and we honestly do not have
any simple fix for this. Just removing the WA-2-2 plate could do serious damage to the
centersection spar. The UND wrap around the end of the centersection spar may have to be
cut and removed. The foam under the WA-2-2 plate must be dug out, the 8 AN525 (or AN509)
screws must be removed (drilling them out may be the easiest method).
A replacement plate must be fabricated, duplicating exactly all
of the holes in the plate. This is a difficult job and will require an expert machinist
and a lot of patience. Brock will not be able to help you with this. Each
case will have to be dealt with on an individual basis. The new piece should be alodined
and then floxed and screwed back into place. If the UND wrap was damaged, it must be
replaced, which requires cutting into the fuel tank (we did say it would be tough!).
This is major work, not anything that could not be done by a
person who has built a VariEze, but very tedious, difficult work. And it must be done
right. There is no short cut, no easy way. If you find more than simple white powder
surface corrosion, stuff you can easily polish off with 320 grit sandpaper, you must
ground your VariEze and replace the corroded parts.
A mandatory inspection is required before next flight for all
VariEzes. Do not take this problem lightly, it could kill you and anyone who may be with
you. Remove both wings. Clean all visible aluminum parts at the wing root and
centeresection spar. Look at the edges of all the WA plates on the centersection spar.
Look for a thinner edge or a swollen appearance under the glass. Look in between these
plates (where the WA-3 tongue slides in). A white powder appearance that can be completely
removed and polished out with 320 grit is OK, but the plates should be very thoroughly
cleaned and sprayed with zinc chromate. LPS or a good quality grease as used in marine
applications should be generously applied everywhere before re-installing the wings. Check
the WA-4 pins and the AN4 bolts and grease both thoroughly. Replace the AN4 bolts if they
show any sign of corrosion.
New construction VariEzes, or anyone replacing wing attach
fittings with new ones, should clean all aluminum parts with Alumiprep 33 or Metal Prep
#79 then alodine them with Alodine 1201 which puts a tough, corrosion-resistant, visible,
golden finish on. We are reluctant to try alodining parts in place due to the acid etch
(Alumiprep 33) possibly getting under the glass onto the aluminum.
When you inspect your VariEze, be very conscientious. Check very
carefully, it is difficult to find, you may have to probe under the glass over the
WA-2-2 plates. Look hard and long at it before you decide it is safe to fly.
The only good news about this is that where the epoxy was bonded
to this WA-2-2 plate which we have, there is no corrosion. The surface of the metal is as
new. Inter-granular corrosion is very common in airplanes that live near the ocean.
Sea planes are especially prone and require constant inspection
and maintenance aimed at preventing just this problem. The salt in the air plus water from
rain or condensation, plus heat and aluminum and, presto!, you have a battery! GaIvanic
reaction and you have corrosion. Keep the aluminum parts clean, grease them often, and you
will have no problems. People who live far from the ocean may not see this problem but
they must check for it just the same.
This problem is confined to the VariEze. The Long-EZ wing
attachment is completly different and this same problem should not occur. Of course, all
metal parts must be protected from corrosion - aluminum with alodine or zinc chromate,
steel with zinc chromate (after cleaning in Metal Prep). Wing attach bolts and parts
should be generously covered with a good grease in VariEzes and Long-EZs. Replace
any rusty bolts and nuts.