Trim tab on 14-13-2

G

Gary Brink

New member
I recall stories of problems with trim tabs on the 14-13- 2...maybe on all of the 14-13s so my question is: If I decide to have an extra hinge put on my trim tab, will that require a 337 or what do I need to make it legal? :?:
Gary
 
I've not heard of this Gary.
I recall 392's trim tab was held on by gap tape and an outboard hinge. Same for you?
 
Hey Gary: Could you do me a favor: I inheritated a basket case project and it seems some rework has been done to my trim tab. How is the actuation lever attached to the tube sticking out of the leading edge of the trim tab. Mine had a screw holding the lever on, but this slips with any pressure....It looks like it needs a drilled hole for a roll pin or bolt or something to make a solid connection????? thanks Ken
 
Ken,
MIne is a brass rod that is threaded and as one turns the trim crank it moves a small brass "thing" that moves the trim tab. (Poor description that doesn't answer your question.) My brass rod and the part that moves on the rod are both worn out as there is a lot of play it them. MPLSTIM (a member) had his come apart in flight and was able to have a new one made, but I haven't found anyplace to make one for my bird yet. (Jump in Tim, or anyone who actually knows what is going on, and answer his question.) :?
Gary
 
Yes, Dave, mine has the outboard hinge and yes they still use the tape that crosses between the trim tab and the elevator but I am hearing that a metal hinge is probably a lot more reliable that the tape. Any other thoughts out there?
Gary
 
The 14-13 series trim tab pivots on two bushings - inner and outer. The actuating arm is actually two metal tabs welded to the tube that is the leading edge of the tab. The bronze 'thing' that is mounted in the actuating arm is a LH trunion nut. The RH trunion nut is mounted on a bracket underneath the elevator. See the drawing in the parts manual. The taped hinge shown in the service bulletin is bare minimum. I prefer a full span hinge made of two two inch tapes sewn lengthwise down the middle. Spread the 'X' tape fore and aft, top and bottom and glue in place. The sew line is now your hinge.
 
That is what is so great about this club. There is so much knowledge out there and it has been unbelievably helpful to me and no doubt to dozens of others who are "winging it" on restorations. Thanks, Dan and Larry. :D
Gary
 
My friend who is an I.A. and A & P made a list of every AD since 1947 for the 14-13-2. Some of them do not apply to my bird but there are a number of them that I need comply with. Lots of undocumented and noncompliant issues to deal with on my plane. I guess it will either keep me out of the liquor store or drive me to it. :)
Gary
 
I find myself in Iraq again until mid-May. The principle is nearly identical to how the landing gear jack screws move the gear up and down. I'll try to remember the thread combinations but I could be mistaken without looking at it... There was a LH threaded insert on the tab held in place with a clevis. A RH threaded insert was fixed on the elevator just forward of the tab. The two inserts had opposite threads so they would work against each other. The actuating rod had to have LH threads on the tab end and I believe corresponding RH threads on the section that passed through the support insert on the elevator. When the rod turns for up trim for example - the rod moves forward in the support insert. The turning rod then causes the tab insert to move forward down the actuating rod, pulling the tab with it. The result is twice the net motion on the tab for the same number of cranks. The rod is moving forward and the tab's insert is moving down the rod pulling the tab with it. When you crank in down trim, the shaft moves aft through the support insert and the tab insert moves aft as well, pushing the tab further up. I happen to think this is a definite Giuseppe-ism and shows his genius in a small detail.

My actuating rod was worn to the point that it slipped through the threaded inserts allowing the tab to flutter. There was enough thread to move the tab but when the force on the tab was too strong, it would slip. I could feel the yoke cycle back and forth in my hand when it "let go" - alarming to say the least. At the time, I was working at an industrial maintenance shop and we had some machinists there that made me new hardware. The machinists recommended oilite bushing material (brass or bronze - I can't remember which) for the threaded inserts for long life and stainless steel for the actuating rod for corrosion resistance. They first made the inserts from the oilite rod stock lathed down to the correct size. Then they drilled and tapped the holes. Threading the new rod was a simple task once we got a LH threading insert. These are silly simple parts for even a rookie machinist and can be made in a matter of minutes. The new parts worked great with no slop and smooth action. If you bring the old parts to a machine shop, they can make you new pieces that will last another 60 years.... I recommend it.

Good Luck

Tim
 
Trim tab failure is no joke. I think it can be deadly. I had this happen in a Taylorcraft. Frightening, was an understatement. I know of four failures in the 14-19 series. In two cases, the tab left the airplane, which was a blessing. Another case caused damage to the airframe and another I suspect caused a fatal accident.
 
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