Elevator hinge play

[Kerrville]

I have a 76 M20j. Just noticed on the preflight a small amount of up and down play (less than 1/10”) in one of the elevator hinges. None of the other hinges have any play. The Mx manual has play limits for the horizontal stab, but none for the elevator. How much is too much?  What is the typical cause, worn bolt vs worn bushing?  If this is an action item I would like to have the parts ordered prior to annual which is coming up in about a month. Thanks for any feedback. 

[EricJ]

Where are you measuring the play?    At the trailing end of the elevator?    It's hard to tell where the slop is from your description.  

[PT20J]

The elevator hinges have ball bearings that should be lubricated periodically. On mine, there is no noticeable play. If the play is at the hinge line a tenth of an inch is a lot. I would investigate this. 

[Kerrville]

Yes, it is at the hinge on the out board right side hinge. If I try to move the elevator vertically right at the line there is a slight movement at this hinge.  There is no movement at any other hinge on either side. Parts manual makes it look like a simple block with an AN bolt through it. I don’t see any bearings in the drawing. 

[Flyler]

That's a lot of slop in a short period of time.  I would suspect the hinge mounts more than wear in the hinge.  Shouldn't be hard to tell where it is coming from in the component if its moving that much.

[EricJ]

7 minutes ago, Kerrville said:

Yes, it is at the hinge on the out board right side hinge. If I try to move the elevator vertically right at the line there is a slight movement at this hinge.  There is no movement at any other hinge on either side. Parts manual makes it look like a simple block with an AN bolt through it. I don’t see any bearings in the drawing. 

Yeah, the IPC isn't much help on these, but they're pretty easy to get at and disassemble/reassemble with some ignition wrenches or similar.    There's usually a bushing or a bearing in there, and with that much play it should be evident what is wearing once it's apart.   You can clamp a couple of boards over the stab/elevator to hold it in place while the fasteners are out.

 

[PT20J]

1 hour ago, Kerrville said:

Yes, it is at the hinge on the out board right side hinge. If I try to move the elevator vertically right at the line there is a slight movement at this hinge.  There is no movement at any other hinge on either side. Parts manual makes it look like a simple block with an AN bolt through it. I don’t see any bearings in the drawing. 

The “block” is a Mooney part that comes with the bearing pressed in. In the field, you would need to press out the bearing and press in a new one. I believe it is a PN-4A https://lasar.com/hardware-bearings/bearing-torrington-pn-4a but you could contact Frank Crawford at Mooney to confirm.

If the bolt isn’t tight, it could be that the bolt shank has worn. You’ll have to take things apart to figure out which parts are worn.

[Kerrville]

I took the bolt out and it looks ok. It appears to be an AN3-11, but that is not what I see in the parts catalogue.  I suspect it is the bushing. Does anyone have experience changing this thing?  Does it require removal of the whole fitting, or can it be done attached to the plane?

[N201MKTurbo]

2 hours ago, Kerrville said:

I took the bolt out and it looks ok. It appears to be an AN3-11, but that is not what I see in the parts catalogue.  I suspect it is the bushing. Does anyone have experience changing this thing?  Does it require removal of the whole fitting, or can it be done attached to the plane?

They are roller bearings. they need to be pressed out and new ones pressed in . You will have to remove the whole elevator to change it. It probably will be OK if you clean and lube them real good. I have noticed when you take off a control surface, the bearings are pretty sticky. They only want to move through the small arc they normally move. If you hose them down with lube and solvent till you wash all the crud out of them, they will spin all the way around without issue. It would be good to pull the control surfaces every decade or so and clean and lube the bearings. But nobody is going to do that....

[Kerrville]

Thanks. I’d rather not have to remove the whole elevator. What do you recommend as a lube on those?

[KSMooniac]

LPS2 is the proper lube for the hinges, but it won't fix a mechanical wear/clearance.  You probably should take the elevator off (it is easy) and thoroughly inspect the hinge fitting and clevis fitting for abnormal wear and cracks.  What you are describing is far from normal.

[EricJ]

+1 that it's not that hard to remove the elevator, and it'll provide much easier access to the hinge components.    You shouldn't have to re-rig anything after reassembly since it doesn't affect the rigging adjustments.    That said, you may be able to free them up as described above and see where the play is coming from and whether it can be alleviated without further disassembly.

[PT20J]

If it really has anything like 0.1" of play there is something more seriously wrong than lack of lubrication. The whole bearing is only 0.63" in diameter. If it were mine, I'd take it apart and figure out what's up. Elevators are pretty critical and looseness might affect flutter margin.

According to the manufacturer, it's a single row ball bearing. I contacted RBC about it several years ago because there were some posts here suggesting that it shouldn't be lubricated because it was sealed and spraying oil into it would wash out the grease. But, according to RBC it is not sealed and should be lubricated periodically with a light machine oil. I use LPS-2. https://productinfo.rbcbearings.com/item/single-row-ball-bearings-standard-series/rbc-airframe-bearing-specials/pn4a-2