The flap actuator is a linear actuator, but the round tube that comes out of it has a tendency to rotate. The force of the motor somehow puts a torque on the rod. This tends to cause the tube to unscrew from the rod end at the top end. This would result in a failure of the flap system. Several such failures have occurred in service.

Van now recommends that the jam nut at the top of the flap actuator be safety wired to ensure it does not loosen. I had been putting off making this mod, as I had such a hard time getting the top bolt in place when I installed that actuator. But, Thursday I had a Eureka moment when I realized that I could unscrew the tube from the rod end and avoid having the remove the rod end from its bracket, which meant I could leave the top bolt in place.

I drilled holes in the nut and the top of the actuator tube. Then I discovered that I couldn't simply use these holes as-is, as the nut would cover up the safety wire hole on the end of the tube. Drat.

I woke up in the middle of the night, and realized that I could solve this problem by cutting a slot in a washer to make clearance for the safety wire. Bingo!

Here is the actuator with the nut safety wired in place. One more item to cross off on the To Do list.