pierre smith
Well Known Member
As I levelled off at 2500' yesterday, I needed some down trim so I pushed the button...WHOA!!...it pitched UP!
The trim indicator bars worked but not the real trim, so I immediately landed. On the ground, I looked over my shoulder at the trim tabs and heard the trim motor running, both up and down, but no motion of the two tabs, so I got out and walked back there.
Grabbing a trim tab, I moved it up and down, the other one accompanying it!
After I removed the tail fairing, the two cables were still attached to the bellcrank but when I reached in there, it moved up and down, when it shouldn't, since it's a pivot point for the trim servo.
Crawling in the tailcone, we saw the AN-4 bolt, castellated nut and a couple of washers lying close to each other! We searched and searched for a cotter key back there but never found one! We put the bellcrank (F-1095B, page 11-9) back in place and this time, cotter-keyed the bolt, since it's a pivot point, and tried the trim and it worked normally.
My gut instinct tells me that there never was a cotter key installed and this airplane has 5+ years and over 500 hours on it and that the nut, then a washer, then the bolt, all progressively fell out over the years and had never been checked during condition inspections!
For all of you -10 guys, remember, it's a rather difficult area to inspect because it's underneath the supporting structure and you probably have to crawl back there to really check it over well.
The airplane, nevertheless, stayed quite controllable, although with considerable forward pressure to hold the nose down, since the tabs had moved downward when I first pushed the "down" button, instead of up, because the whole assembly moved toward the front of the airplane, pulling the tabs down, and the pitch up.
Whew! Yes, I did say a "Thank You" prayer
Best,
The trim indicator bars worked but not the real trim, so I immediately landed. On the ground, I looked over my shoulder at the trim tabs and heard the trim motor running, both up and down, but no motion of the two tabs, so I got out and walked back there.
Grabbing a trim tab, I moved it up and down, the other one accompanying it!
After I removed the tail fairing, the two cables were still attached to the bellcrank but when I reached in there, it moved up and down, when it shouldn't, since it's a pivot point for the trim servo.
Crawling in the tailcone, we saw the AN-4 bolt, castellated nut and a couple of washers lying close to each other! We searched and searched for a cotter key back there but never found one! We put the bellcrank (F-1095B, page 11-9) back in place and this time, cotter-keyed the bolt, since it's a pivot point, and tried the trim and it worked normally.
My gut instinct tells me that there never was a cotter key installed and this airplane has 5+ years and over 500 hours on it and that the nut, then a washer, then the bolt, all progressively fell out over the years and had never been checked during condition inspections!
For all of you -10 guys, remember, it's a rather difficult area to inspect because it's underneath the supporting structure and you probably have to crawl back there to really check it over well.
The airplane, nevertheless, stayed quite controllable, although with considerable forward pressure to hold the nose down, since the tabs had moved downward when I first pushed the "down" button, instead of up, because the whole assembly moved toward the front of the airplane, pulling the tabs down, and the pitch up.
Whew! Yes, I did say a "Thank You" prayer
Best,