Thread: Stabilator

Hi Guys,
This is just a nice preflight double ceck.
What I'm about to say has nothing to do with a real plane issue, but a human caused one.

During your next preflight back at the stabilator I know many try to rock the stabilator up and down to see if the can feel or hear anything out of place.
But now try and move it fore and aft on its horizontal plane. Push the left side towards the cockpit and see if the right side moves aft. Try to rock it fore and aft in its horizontal plane. It should not move and should be snug.
If it moves fore and aft then it needs to come off (not hard to do) and put a wrench on the Rotation pin/bolt. This pin is what the stabilator rotates on and has a nut on each end. The nuts should be torqued to 200 in/lbs. If your stabilator does rock fore and aft this torque should be checked. I did just find one that another mechanic stripped and wouldn't tighten down at all which allowed the stabilator to move fore and aft. It will be a very small move, but none the less it's there and shouldn't be. I just replaced the pin and two new nuts and torqued them to the FD specified 200 in/lb. The stabilator now was snug and had zero movement fore and aft. Left with this motion I'm sure over time damage would get worse. If you have any tail flutter this is a good area to check all the nuts and bolts for torque.


Tip of the Day:

One further note. The mechanic that put this back together only had small nuts holding the trim tab control rods in place. When I was flying helicopters the biggest fear was having a control rod failure and have the rod end just come out and the rod would then just slip right over the rotating center past the nut and then you had loss of control.
Here is what I was taught for rod end safety a long time ago. Put a thin small washer with a large enough surface area between the bellcrank and nut so if the bell crank does fail the rod end can not come off over the nut. This way even if the rod end does fail you keep control.

Roger,

just in time with this advice [again ].

I have this type of small movement [fore&aft] and I've thought that can wait for 200h revision...
But this issue is already annoing to me and with your tips I'll would like to solve it as soon is possible.
So, to be sure, reffering at page 4-74/AU 010 02000 are you kind to confirm that in your tip:
1. "to come off" [the stabilator] means just to disconect the control rods for trimtab and to take off the braket bolts C9996259N?
2. the "pin" is KA3010001 and the "nuts" that should be checked/torqued 200 lb-in are C9996336?

Thanks,
Alec

Hi Alec,

Sounds like you got it.

Remove the two 9mm nuts on the trim control rods just under and inside the rear section of the tail. Slide the rods off to each side off the pins they are mounted on. Then remove the two 10 mm nuts on the bottom of the stabilator from the two mounting bolts. The stabilator now comes off. The two large nuts on either end of the rotation pin will now be exposed and you should be able to put a torque wrench on them. Be sure the rotation pin just doesn't turn even when you have a wrench on the other side. The torque on these two nuts are 200 in/lbs. After you are finished just reverse the process. The 10mm nuts on the bottom of the stabilator are torqued to 80 in/lbs.

It doesn't take too long and it's not that hard. The hardest thing is taking off and putting on those two small 9mm nuts for the control rods.

ok, everything very clear now, thanks.

Alec

I thought we were supposed to be getting an SB regarding the stabilator this fall. Any news on that front? - WF

It's due anytime. No way to tell exactly when. I was told right about now so we'll just have to keep our eyes open. It's a matter of getting all the parts, people and service in place and ready to go at the same time.

Originally Posted by gisurvey

[...]
I have this type of small movement [fore&aft] and I've thought that can wait for 200h revision...
But this issue is already annoing to me and with your tips I'll would like to solve it as soon is possible.
[...]

ok, job done.

good news: indeed, a simple work to do [if you know what to do ], the nuts looked visualy ok, secured with red seal [that is original position].
now, after this little work, there is absolutely no unwanted movement, resulting in a happy stabilator and a confident owner

somewhat bad news: the nuts were pretty loose, at least one turn [difficult to say exactly, but clearly more than 1 turn] has to be torqued each to 22.5 N*m.

Roger, thanks again for yours invaluable advices.

Hi All,

FYI

This is an update to the first post on this subject. I just found my third stabilator that had fore and aft free play. After I removed the stabilator I found the pivot pin bolt nuts stripped again. This is the third plane I have found this way. The nuts will not torque, but only spin and never tighten. When you do your pre-flight grab your stabilator and try to move it fore and aft on one end. It should not move. The movement fore and aft is slight, but noticeable. I was able to remove these nuts and the pivot pin was in good condition. I was able to just replace the nuts and torqued them to 200 in/lbs. These came from the factory and have been on both the SW and LS. I hope FD reads this and maybe consider a little lesser torque value to maybe 180 in/lbs.