Bob –
I too, like yourself, fly high 90% of the time (although I don’t
have the power to get to 250!), from FL190-230 on routine 3.5-4.5 hour flights
from the Midwest to AZ. What surprised me in your email is that you max
out the internal pressure all of the time. I actually set the altitude
controller to target altitude in all cases and live with the 7-9k k cabin
altitude way up high (which never actually commands 5.5 differential, more like
4.5-5.0 in my plane). My question would be, is the airplane designed to
handle the 5.5 psi differential all of the time? My airplane has 1500 hours
on it now with no problems like you describe. I do have some cracks in
the paint around the fuselage outside of the door but I think they are normal
wear for a 1500 hour paint job (not sure of this, just guessing). I would
check with Lancair and see what kind of long term testing they did before you
redo it, so you can either strengthen the door or modify your flight
procedures.
Bob R
IV-P
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