Lancair builders,
Two weeks ago, I discovered what appeared to be about a 1”
“crystallization” just visible by looking through the Plexiglas at
an angle within the carbon fiber “sandwich” holding the door window
in my Lancair IV-P. This is just visible in the attached photos of the upper
back corner of my cabin door. It’s in the lower center of the “outside”
photo; upper center of the “inside” photo, and is directly across
the door frame from the upper rear door latch.
I asked Bill Harrelson to have a look at it on Saturday, and by
that time, the small defect I originally saw had clearly spread to a crack
of about 4” running from below the original crystallization area to the upper
back curve of the window. The pictures show the resulting crack generated in the
interior and exterior paint.
Brent Reagan sent detailed pictures and instructions on how to repair
this (MANY THANKS BRENT), and I am ready to pull the door and start cutting out
the window for replacement. Fortunately I have an extra window available from
buying the “fast build door” in 2004 after buying the complete kit,
with window, some years earlier; but before I cut into it, I was trying to
figure out what’s caused this, and seek your advice on how to prevent a reoccurrence.
The background: The complete fast build door was installed in
2004 and the aircraft painted in 2006. It first flew in June, 2008 and has just
over 500 flying hours to date. I normally fly in the high teens/low flight
levels, but tested the airplane to FL250 and have been there a few times since
to avoid weather. I normally leave the cabin altitude controller set at 1000’,
generating the rated 5.5 PSI pressure differential any time the aircraft is
above 14,000’ or so. I would estimate the airplane has 200-250 hours at
5+ PSI. I first noticed the crystallization while cleaning the windows. There
was no crack visible at that time, and the defect was directly across from the
upper rear door latch. Note also that the door lift strut attaches to the door
frame just above this point. This new strut attach location was incorporated in
the factory fast build door that I received.
I have been very careful with the door and have not had any
problems with it at all. It closes and latches easily without binding, and with
very light pressure on the closing handles. The only possibly-related thing that
I can think of is that I left the airplane for a minor servicing last month,
and the maintenance crew worked it on the ramp on a windy day. It’s
possible that the door was opened by someone not familiar with it, and allowed
to extend upward hard against the lift strut by the wind. I don’t
know this to be a fact, but it’s the only possibility I can think of—and
even so, the flaw did not start at the lift strut attachment point. I flew
the airplane at 17,000’ (full 5.5 PSI differential pressure) for three
hours after the maintenance work, and flew it four more times in the local area
with the cabin partially pressurized. Lucky?? Another explanation??
Any thoughts/comments appreciated. Also, is there anything I should
look for as I cut out the old window?
Many thanks in advance,
Bob Pastusek