Spar Cap Replacement

**Pinecone** · February 15

Asking for a friend. REALLY

An A&P I know did a PPI on a Mooney that has been sitting for a while. He and I agree that the potential buyer should walk away, but the buyer wants some price ranges to fix.

The A&P found corrosion of the main spar cap visible inside the wheel well (I will see about getting pics). So, can you replace the main spar cap or the entire main spar? And what ball park of cost?

This aircraft also has corrosion of steel cage members and severe (A&P words) pitting in the cylinders.

Thanks

**EricJ** · February 15

Spar caps can be changed out, but it's not cheap. I think Alan Fox managed to do one that was perhaps "minimally invasive", but was still a project. Probably also matters whether it is top or bottom, how bad, what else is affected, etc.

**47U** · February 15

6 minutes ago, Pinecone said:

So, can you replace the main spar cap or the entire main spar? And what ball park of cost?

If the corrosion is that extensive that you’re talking about replacing the entire main spar, I think you’re money ahead to replace the whole wing.

Wing replacement is the ‘ball park cost’ you’re looking for.

A64Pilot · February 15

100K

Based on engine overhaul, maybe not but you have to plan on the worst, and a WAG on wing replacement, I don’t have knowledge to make a SWAG

Then add in the steel tubing, no way is any old airplane worth it, my reasoning is that the corrosion is throughout, it’s not just a spar cap and steel tubing.

‘Value is likely whatever salvage is

Edited February 15 by A64Pilot

**LANCECASPER** · February 16

8 hours ago, Pinecone said:

Asking for a friend. REALLY

An A&P I know did a PPI on a Mooney that has been sitting for a while. He and I agree that the potential buyer should walk away, but the buyer wants some price ranges to fix.

The A&P found corrosion of the main spar cap visible inside the wheel well (I will see about getting pics). So, can you replace the main spar cap or the entire main spar? And what ball park of cost?

This aircraft also has corrosion of steel cage members and severe (A&P words) pitting in the cylinders.

Thanks

@redbaron1982 had this repair done a few years ago and could probably provide some insight on cost and time involved.

bigmo · February 16

I hope that plane is free.

**Fritz1** · February 16

Wing toast, engine toast, roll cage tubes rusted, the nice thing about salvage ist that a lot of the other parts will fly again

redbaron1982 · February 16

13 hours ago, LANCECASPER said:

@redbaron1982 had this repair done a few years ago and could probably provide some insight on cost and time involved.

It was the aft stub spar, not the main. Repair cost was 27.5k and took 1 year. It was done by Don Maxwell.

1980Mooney · February 16

1 hour ago, redbaron1982 said:

It was the aft stub spar, not the main. Repair cost was 27.5k and took 1 year. It was done by Don Maxwell.

Just curious - how did you get it to him in Longview? Was it able to fly under a Ferry Permit? Or did it have to be disassembled and transported? If so does the $27.5K include transportation?

redbaron1982 · February 16

35 minutes ago, 1980Mooney said:

Just curious - how did you get it to him in Longview? Was it able to fly under a Ferry Permit? Or did it have to be disassembled and transported? If so does the $27.5K include transportation?

A ferry permit. The 27.5k was the repair alone.

Specifically this is the description under the 27.5k item:

"Removed lower belly panels, flaps, elevator and rudder control rods. Removed seats and interior. Removed upper and
lower rear seat panels to access TKS tank and pump. Removed TKS tank and pump. Removed both main landing gear.
Removed aft spar due to corrosion. Replaced aft spar with new aft spar from Mooney Pn. 210054-905. Replaced lower
spar center section panel Pn.210073-000 due to corrosion. This is the panel TKS tank sits on. All corrosion associated with
TKS leakage into this panel. Reinstalled removed items.

Painted repaired areas and lower wings"

One clarification regarding the paint, only the repaired areas were repainted, not the whole lower wings. I would estimate that 10% of the lower wings surface was repainted.

Edited February 16 by redbaron1982

**MikeOH** · February 16

36 minutes ago, redbaron1982 said:

All corrosion associated with TKS leakage...

If I had a plane with TKS, I would find that comment VERY disturbing

redbaron1982 · February 16

19 minutes ago, MikeOH said:

If I had a plane with TKS, I would find that comment VERY disturbing

I do, lol.

But I really don´t know how much myth is behind this. The corrosion issue that I had in the first place (the aft spar cap) most likely was a manufacturing process issue. The type of corrosion was intergranular, which to my understanding is not much due to external factors, but more the heat treatment / manufacturing process.

The airplane, besides that issue, is completely clean, I don´t see any signs of corrosion anywhere else. I haven't look at the additional corrosion mentioned by Don in the report, he didn't provide any pictures.

**EricJ** · February 16

On 2/15/2025 at 8:52 AM, 47U said:

If the corrosion is that extensive that you’re talking about replacing the entire main spar, I think you’re money ahead to replace the whole wing.

Wing replacement is the ‘ball park cost’ you’re looking for.

And the wing can be replaced with a logbook entry. It is not a major repair.

**MikeOH** · February 16

1 hour ago, EricJ said:

And the wing can be replaced with a logbook entry. It is not a major repair.

According to the FAA or your checkbook?

**cliffy** · February 16

Like for like part- Just check P/Ns and tracing back to the donor airframe (you have to have the tracing back to donor

to qualify as an "approved part" for installation)

Log book sign off only

No different than a flap or elevator

redbaron1982 · February 16

In my case, for the spar replacement, I didn't get a form 337. I talked with Don about this and he told me "there was no repair performed, just a part replaced".

**GeeBee** · February 16

Run Forest, run!

**Pinecone** · February 17

Here is the picture.

A&P and I figured total to be $150,000 or more to deal with known issues, and more could come to light.

A64Pilot · February 17

On 2/16/2025 at 11:58 AM, EricJ said:

And the wing can be replaced with a logbook entry. It is not a major repair.

I hate to keep disagreeing but if we look at the definition of major repair I believe if the wing installation is incorrectly done it could certainly cause structural strength problems and flight characteristics both. I believe there is nothing elementary with replacing a Mooney wing either in my opinion, but most Cessna high wings are pretty rudimentary, but I guess that depends on the opinion of what rudimentary means, but I don’t think I could keep a straight face trying to tell an FAA inspector that replacing the wing on a Mooney isn’t a major.

That, if improperly done, might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or

(2) That is not done according to accepted practices or cannot be done by elementary operations.

A64Pilot · February 17

Hidden damage is most often the gotcha in things like this, you open it up to replace something and all the additional stuff you find has to be fixed too and on an old airplane it can be substantial.

When we first reopened Thrush many wanted the new 29,000 hour spar cap installed in their wings instead or just replacing them with the originals that would time out in 5400 hours so we developed a custom kit and started doing them, after 8 or 10 wings I stopped, the reason why was by the time I fixed all the cracked ribs, replaced the corrosion in 30 year or older wings and did the work to install the 29,000 hour cap the cost was approaching the price of a new set of wings, it just wasn’t smart, for a little more instead of a repaired 30 plus year old wings you could get a brand new set, plus the downtime was substantial, where I could put a new set on in a couple of days.

Sometimes repairing just doesn’t make sense unfortunately.

**DCarlton** · February 17

40 minutes ago, Pinecone said:

Here is the picture.

A&P and I figured total to be $150,000 or more to deal with known issues, and more could come to light.

Help me out here. Not a corrosion guru. If all the paint were stripped away down to bright metal, where would the worst corrosion be?

Mark89114 · February 17

24 minutes ago, DCarlton said:

Help me out here. Not a corrosion guru. If all the paint were stripped away down to bright metal, where would the worst corrosion be?

was wondering the same thing....I just see flaky paint......

I am just an internet expert.....

**hammdo** · February 17

Where the huck bolts are looks like corrosion…

-Don

A64Pilot · February 17

1 hour ago, Mark89114 said:

was wondering the same thing....I just see flaky paint......

I am just an internet expert.....

I’m thinking there may be a significant number of aircraft like that, that have paint over that if I’m seeing what I think I am

I think this is the corrosion? I’d circle it in red if I knew how, but instead I just blew it up

Edited February 17 by A64Pilot

**47U** · February 18

5 hours ago, A64Pilot said:

That, if improperly done, might appreciably affect …

This statement is just a bit open-ended.

Sounds like a catch-all statement allowing the FAA to hold a mechanic accountable for anything and everything.

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