Heat-Induced Control Interference

Posted July 2015

Seattle has a very temperate clime... temperatures almost never get above 100 degrees F, and almost never drop below 0 F.

Until this year, the record for the number days per year above 90 degrees was *three*.

This year is different.  We're up to about seven.

Today was one of them...about 95 degrees, absolutely beautiful day to fly an open cockpit airplane.  I took Moonraker up, flew around for about 40 minutes, then came back and landed.  As I rolled out, I decided I wanted more.  But the fuel was a tad low, so I pulled up to the pumps to get it filled.

After a bit, I fired up and taxied out to the runway.  Start pre-takeoff checks....

Hmmmm.  The ailerons are sticking.  They'd go to the right just fine, then come to neutral and lock.  A bit more pressure and it'd clear....

But, shoot, somethings wrong.  I taxied back to the hangar and shut down.  After pulling out my ear plugs, I wiggled the stick back and forth.  There was a distinct "Thud" when the stick went left of neutral, synchronized with the sticking.  Following my ears, it seemed to be coming from the aileron itself.

I climbed out and took a closer look.  The inboard aft edge of the aileron was striking the end corner of the aileron notch in the wing. I could work things by hand, and actually feel the surfaces rub across each other.

No other sign of issues...no buckled ribs, no wrinkled fabric.

The only thing I could think of was the heat, and the fact that the airplane sat out in it, stationary, for about 30 minutes.

I pushed it back into the hangar.  Five minutes later, the interference was gone, and there was a gap about the thickness of a business card where the pieces had been striking, before.

Pretty amazing.

The lesson here?  Don't build your airplane with really tight clearances for the ailerons.  This plane has been flying for over 30 years, I've been flying it for nearly 20, and this is the first time this has happened.  I'm going to shave some material off the edge of the aileron, but there's no reason for it to be this close to start with.  Give yourself some room, folks....

Ron Wanttaja

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