Trim fail

I had a bit of a scare last week.

Just after take off I heard a 'bang' and had to use more back pressure on the stick than normal to keep the climb attitude the same.

I decided to continue to climb up to a safe altitude - 3,000 ft - before investigating what had gone wrong.

After thinking about it for a little while I concluded that one of the trim springs must have either broken or come loose.

The rest of the flight continued without incident and I made a normal landing. The stick forces were not much more than normal - thankfully the Twister does not really need a trim in the first place as the forces are so light.

That evening I investigated and sure enough the rear spring securing bolt had come right out. 

This explains the stick forward bias as only the front spring was acting against the elevator push rod tube - requiring a constant rearward force to overcome it.

I noticed that the bolt thread did not have evidence of Loctite on it so that is a failure on my part. It's taken just over 400 hours for this to happen.

I've used Loctite this time! And also added TorqueSeal to the outside so that at each annual it can be inspected for movement.

Something to be aware of if you have not used Loctite - but certainly an inspection item (with the TorqueSeal) to add to the Annual if you have already not done so.

After removing the baggage tray it was instantly obvious what had happened. The bolt holding the rear spring had worked loose and come completely out.

Closer view.

After fixing with Loctite on the thread of the bolts and also now with TorqueSeal (in Blue) which will aid inspection.