Kevin Horton
Well Known Member
Motivated by elevator spar cracks found by one RV-7A owner , and Tony Kelly's tragic accident on Friday, I conducted a detailed inspection of the empennage on my RV-8 today. I'm very, very glad I did this inspection, as I found a significant, but easily fixed issue. I'm lucky to have found the issue before it progressed to its logical conclusion, because the results could have been very, very bad.
As I was laying under the left side of the tail, I flexed the elevator trim tab, and there was a bit more play than I expected. Looking closer, it seemed that the majority of the play was coming from inside the elevator. It looked like the trim servo was moving in its mount. I removed the panel that the trim servo is mounted to, and was horrified to see that three of the four nuts that secure the bolts holding the servo to its mount were missing. Two of the bolts were also gone. The only thing holding it in place was one bolt and nut, and a bolt without a nut on the diagonal corner. I shudder to think what would have happened if that last nut had come loose.
It looks like I used temporary hardware to attach the servo to its mount, as I obviously didn't use lock nuts or Lock Tite. I must have done a trial fit with temporary hardware, and forgot to later remove it to install the proper flight hardware. This would have been early in the project, when I still had the illusion that my memory was perfect. I later learned to never, ever assemble something with temporary hardware, or without the final torque, unless I added an unmistakable visual clue that more work was needed. I started hanging pieces of fluorescent tape from parts that had temporary hardware, or were not final torqued.
As I was laying under the left side of the tail, I flexed the elevator trim tab, and there was a bit more play than I expected. Looking closer, it seemed that the majority of the play was coming from inside the elevator. It looked like the trim servo was moving in its mount. I removed the panel that the trim servo is mounted to, and was horrified to see that three of the four nuts that secure the bolts holding the servo to its mount were missing. Two of the bolts were also gone. The only thing holding it in place was one bolt and nut, and a bolt without a nut on the diagonal corner. I shudder to think what would have happened if that last nut had come loose.
It looks like I used temporary hardware to attach the servo to its mount, as I obviously didn't use lock nuts or Lock Tite. I must have done a trial fit with temporary hardware, and forgot to later remove it to install the proper flight hardware. This would have been early in the project, when I still had the illusion that my memory was perfect. I later learned to never, ever assemble something with temporary hardware, or without the final torque, unless I added an unmistakable visual clue that more work was needed. I started hanging pieces of fluorescent tape from parts that had temporary hardware, or were not final torqued.