Has Anyone Repaired the Tail Cone?

[GeeBee]

Doing the annual on my airplane I pulled off the fairing for the tail assembly. I found a crack in the bottom, the I looked up at the tail cone and found the crack was caused by the tail assembly rubbing against the fairing. Has anyone seen or repaired this type of damage?

[KSMooniac]

Re-skinning would likely be the best solution here.  It is too bad it went un-noticed long enough to do that much damage.  A good sheet metal mechanic might be able to reskin with flat sheet, but I'd first inquire with your favorite MSC if there are factory skins available for this part... I suspect they might have or make one, and it won't cost terribly much, at least by modern standards.

Failing those options, a good sheet metal mechanic might be able to craft a repair per 43.13-1B and do a local patch.

[Yetti]

Was the plane gear upped at some point in it's life?

[GeeBee]

9 minutes ago, Yetti said:

Was the plane gear upped at some point in it's life?

No. This is simply the fairing rubbing against the tail cone.

 

[IvanP]

37 minutes ago, GeeBee said:

No. This is simply the fairing rubbing against the tail cone.

 

That must have been a lot of rubbing to cause this level of damage. Was the fairing installed right?

[GeeBee]

26 minutes ago, IvanP said:

That must have been a lot of rubbing to cause this level of damage. Was the fairing installed right?

The last time it was installed, it was done by an MSC.

 

[PT20J]

From the photo, it looks like the damage is on the empennage stringer rather than the tailcone. Item 12 in the drawing. Really odd that the fairing could do so much damage as it is pretty thin and I’d expect it to wear through first. The damaged skin may be structural. Frank Crawford can supply repair instructions. 

[LANCECASPER]

I have never seen that in any of the seven Mooneys I've owned. My guess is that a previous owner had a hard landing with a tail strike.

[GeeBee]

37 minutes ago, LANCECASPER said:

I have never seen that in any of the seven Mooneys I've owned. My guess is that a previous owner had a hard landing with a tail strike.

I've owned the airplane for almost 6 years. It's been to Maxwell, Cole, Precision Air. I've removed that fairing myself, 4 years, except for last year. If a hard landing with a tail strike was the case, it would have shown up earlier and I would have seen it. This happened over the last year.

[1980Mooney]

2 minutes ago, GeeBee said:

I've owned the airplane for almost 6 years. It's been to Maxwell, Cole, Precision Air. I've removed that fairing myself, 4 years, except for last year. If a hard landing with a tail strike was the case, it would have shown up earlier and I would have seen it. This happened over the last year.

Does anyone else fly your plane?  Test flight by any shop?

[GeeBee]

22 minutes ago, 1980Mooney said:

Does anyone else fly your plane?  Test flight by any shop?

No.

The opening has been enlarged as we removed material that had been eroded by the fairing. When we took the fairing off, it had a crack at the crease. A look at the empenage showed scraping. We used a screwdriver and found the metal foil thin. We then removed the eroded metal with a finger tip to create the gap you see in the photos.

[1980Mooney]

2 hours ago, GeeBee said:

Doing the annual on my airplane I pulled off the fairing for the tail assembly. I found a crack in the bottom, the I looked up at the tail cone and found the crack was caused by the tail assembly rubbing against the fairing. Has anyone seen or repaired this type of damage?

It 

 

28 minutes ago, GeeBee said:

No.

The opening has been enlarged as we removed material that had been eroded by the fairing. When we took the fairing off, it had a crack at the crease. A look at the empenage showed scraping. We used a screwdriver and found the metal foil thin. We then removed the eroded metal with a finger tip to create the gap you see in the photos.

Since you have removed the empennage fairings previously, you know that they are just 2 pieces of flat aluminum attached by screws.  They are not attached together at the bottom. They are open at the bottom.  There is no way for them to make physical contact with the bottom of the stinger skin.  Yes they can rub the side but not the bottom.

It is hard to tell from the picture but as I look at it again, both the stinger bulkhead and the stinger skin which you have cleaned up the "eroded metal" look like they are heavily corroded.  Is it thin from corrosion?

I notice that you have a TKS plane.  Could TKS fluid from your empennage leading edges pool down there?

 

[GeeBee]

49 minutes ago, 1980Mooney said:

It 

 

Since you have removed the empennage fairings previously, you know that they are just 2 pieces of flat aluminum attached by screws.  They are not attached together at the bottom. They are open at the bottom.  There is no way for them to make physical contact with the bottom of the stinger skin.  Yes they can rub the side but not the bottom.

It is hard to tell from the picture but as I look at it again, both the stinger bulkhead and the stinger skin which you have cleaned up the "eroded metal" look like they are heavily corroded.  Is it thin from corrosion?

I notice that you have a TKS plane.  Could TKS fluid from your empennage leading edges pool down there?

 

No on my airplane, one side curls around the bottom and the other side fits inside the curl.

That is not corrosion, it is dark from the photo artifact and corrosionX

If you look at the paint on the skin, the scraping stops at the end of the fairing mark.

[PT20J]

The fairings are not all the same. Later models do wrap around the bottom. 

I don’t think it would be possible to have a tail strike hit this area without serious damage to the tail tie down and rear bulkhead of the tail cone. 

But regardless of how the damage occurred, the issue at hand is how to repair it and prevent recurrence. 
 

[GeeBee]

I know it is not a tail strike because the paint on the fairing is shiny and undamaged. Bulkheads are all intact. Again if you notice the scraping took place underneath the fairing.

[Ragsf15e]

22 hours ago, 1980Mooney said:

It 

 

Since you have removed the empennage fairings previously, you know that they are just 2 pieces of flat aluminum attached by screws.  They are not attached together at the bottom. They are open at the bottom.  There is no way for them to make physical contact with the bottom of the stinger skin.  Yes they can rub the side but not the bottom.

It is hard to tell from the picture but as I look at it again, both the stinger bulkhead and the stinger skin which you have cleaned up the "eroded metal" look like they are heavily corroded.  Is it thin from corrosion?

I notice that you have a TKS plane.  Could TKS fluid from your empennage leading edges pool down there?

 

I had a look at my ‘87 K model today, and sure enough, one side of the fairing curls underneath the tailcone and there are two “drip holes” in the bottom.  My old airplane wasn’t like that, just two flat pieces that didn’t go under.

[1980Mooney]

Well, considering the damage that the curled fairing did in only one year to the skin of the stinger on @GeeBee's plane, one might consider going back to the simple old style flat sheet fairings.  The curled fairing, while well intentioned, seems like a bad idea in practice - it has only been touched/installed by top shops and the owner yet it created substantial damage.  That large stinger skin is cut at the crease and as @PT20J says it may be structural. It also looks like the skin is severely abraded about an inch or two above the crease.  I suspect that the empennage needs to be removed in order to replace the stinger skin.  Perhaps it could be patched but it will no longer be a smooth surface for the fairing to rub against as the trim is changed and the empennage tilts, and it will be noticeable.  

It is unfortunate.

 

 

 

 

 

[PT20J]

My 1992 J has the fairing that curve under the tail and they don't cause wear on the empennage skin. Something is unusual here, without examining it, I have no idea what the problem is.

[GeeBee]

Here is what I have found out. We looked at some other long bodies and they all have much more clearance between the fairing and the tail than my airplane. On the order of 1/4 inch or more. It appears someone some time ago put a washer between the fairing and the riv-nut to create clearance. The washers are not in the IPC. I don't know if this was a factory adjustment to some poorly fitted fairings or not. I checked the parts bag for the faring this time and those washers were missing. So whoever removed the fairing last time, did not put the washers back where they belong creating the interference. There have been multiple facilities that have worked back there the past year since I last installed the fairing in November of 2022 so I don't know "who dun it".

After consultation with numerous Mooney experts including Robert at Lasar, Joe Cole et al and calling in a DER it has been determined the skin is not structural. It can be patched and the DER is coming up with a drawing for the repair. It will require re-fitting or re-manufacturing of the fairings to make it work, but there will be more clearance this time.

If you have the curl type fairing, check your clearance.

Thanks for all your input. 

[KSMooniac]

I can assure you that skin is indeed structural, but the area of your damage is likely not critical since the main loads are likely reacted out by the "box" structure that has #28 (from the IPC pic) backing up the trim attachment as the lower bound of the "box" I'm describing.  The skin carries load in monocoque and semi-monocoque (what we have with a Mooney) aircraft structure.

Good luck with the repair.  I still think it might be easier to replace the entire skin, assuming you can get it from Mooney.  It might be cheaper than the DER too.  In the past 4 years I've purchased aileron, elevator, vertical stab and roof skins for hail repair from the factory (through an MSC).

[PT20J]

I looked at mine today. There is a lot of clearance with the tail in takeoff trim position. But, it would be easy to deform the fairings if, for instance, the airplane was lowered off jacks onto something (not saying this is what happened to @GeeBee's airplane -- it's just a possibility). There is a drain hole in the bottom of the stringer skin and the fairing that should be kept clear. I had previously put some Teflon anti chafe tape on the inside of the fairing. Anyway, it appears that this is an area that might be overlooked during inspection and might be good to give it attention.

[Falcon Man]

It has been published prior that the skins of the M20 Moony are not structural. Is this an exception/

 

[1980Mooney]

22 minutes ago, Falcon Man said:

It has been published prior that the skins of the M20 Moony are not structural. Is this an exception/

I think you are referring to the skins on the fuselage around the steel cage.  The skins on the fuselage/tail aft of the backseat are absolutely structural of semi-monocoque design.  Then think about the construction of the rudder and elevators - they are each just two skins of aluminum with corrugations for strength mated together.  I think that is monocoque design - but in any event the skins are structural.

Edited February 20 by 1980Mooney

[Falcon Man]

Thanks for that clarification!

 

 

[KSMooniac]

1980 is correct.  The only non-structural skins on a Mooney are the cabin area around the steel cage, and any fairings like the empennage gap fairings, dorsal fairing (metal on the vintage birds), wing roots, gear doors, etc.  The tailcone, empennage, wing, and control surface skins are all structural.