visioneer_one

My Feedback: (506)

I had my UCD3D ou today, putting on an impromptu aerobatics display for one of my co-workers. I was flying downwind at WOT over the field, rolled left 1/4 turn to knife-edge, then did two rapid rolls to the right, ending upright.

After releasing stopping the roll and releasing stick pressure the plane abruptly rolled to the right. I caught it and righted it... it did it again!

***! Broken control rod, broken clevis, stripped gears?

Pulled the power back and fought it for a couple of seconds... it kept trying to roll to the right, then suddenly started acting normal. I spun the plane around, hit the spoilers and landed uneventfully.

The cause?



The entire top case of the servo was cracked and loose. The lugs are intact - it seems like the cracks originated from the screws that hold the case together.

I figure that the top of the servo lifted up and jammed the gears during the rapid rolls, then (luckily!) snapped back into place after a few seconds.

A quick inspection of all the rest of the servos in this plane reveal the same thing - the top cases are all cracked, some more severely than others. One of the elevator servos' top case is cracked completely across the top, right behind the output shaft!

These are the old FMA 3601/3601M coreless servos. These servos were new when I installed them - I bought a bunch when FMA closed the mout two years ago.

I've got a bunch more of these servos in use in other planes. You can be sure they will all get some careful scrutiny before I fly them again!

Lynx

Either the case screws were tightened too much, or the plastic formulation was off a bit and was made too brittle. Or both.

AJF--2

My Feedback: (119)

In my 13 years of flying, I don't think I have ever seen that!