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