Shops to Replace 172 Flap Rails

[ARFlyer]

Our 172 is about to need the flap rails replaced due to wearing and our A&P is kinda skittish of completing it for understandably obvious reasons.

Does anyone know of any speciality shops that would complete the replacement? I’ve looked at Williams but I REALLY do not want to take the wings off and ship them for the job.

 

[Gary Ward]

Our 172 is about to need the flap rails replaced due to wearing and our A&P is kinda skittish of completing it for understandably obvious reasons.

Does anyone know of any speciality shops that would complete the replacement? I’ve looked at Williams but I REALLY do not want to take the wings off and ship them for the job.

It would seem it necessary to remove the wings to be able to do it? It would seem easier with the wing upside down? But I have no idea? Good luck with it.

Williams has nice grass landing strip, but it is private I am pretty sure. I asked them one time if I could fly in and he said no. Be cool to fly in and get new wings!! lol

 

[Bell206]

Does anyone know of any speciality shops that would complete the replacement

While I can't recommend a shop no longer, any shop that offers sheetmetal services should be able to replace the tracks. The track replacement can be done with the wings installed. Highly recommend using the McFarlane tracks as they are better than OEM. Perhaps go on a type forum and inquire on possibilities in your region. Fully understand why your AP is a bit hesitant as a number of mechanics don't practice the S/M side much. The track replacement is not technically difficult but it's not a job to resharpen your rivet drilling/banging skills on. Good luck.

 

[Gary Ward]

I am surprised that there are virtually no U tube videos of the process to replace them. I only could find 3 very brief videos that were mostly worthless. McFarlane had a couple showing their tools for inspection which are good but very brief.

Does seem like black art?

 

[Bell206]

I am surprised that there are vitally no U tube videos of the process to replace them.

Does seem like black art?

No black art. Its actually basic AC43.13-1B stuff. As to no mx videos, I don't find it that unusual or surprising there are very limited examples especially on the S/M side. While there are a number of professional mx training videos out there covering a multitude of tasks on both airplanes and helicopters, I think the youtube platform videos are more subjective to the person for whatever reason they post their aircraft mx videos. Whether that's a generational thing or something else I cannot answer that.

 

[martym]

Not difficult but it is time consuming with a lot of drilling and riveting. Interesting an A&P would turn it down. That's a money maker.

 

[Magman]

It’s not clear to me what the “ obvious” reasons are. From what I’ve seen this is one of those “ How long is a piece of string?” projects. You don’t really know hoe involved it will be till it’s done.

My recall :

Defuel the aircraft.

Remove fuel tank covers and tanks Ugh! Tanks ok?

There is a spanwise panel about 1 foot wide and the length of the flap . Drill out rivets and remove it.

You should now have complete access to the inboard flap track attach and access to the rear only of the outboard track.

Gaining access to the front side of the outboard track requires de-riveting of skin forward of the previously removed panel. This is done to allow bucking of the new rivets.

Drill out existing rivets and install tracks and reinstall skin.

I think that is how it was done.

CAUTION

Maintaining proper wing wash-out is ESSENTIAL. As rivets are removed the wing becomes more flexible. The Cessna Manual details an easy procedure to assure wash-out is correct. Accomplish this easy check while the wing is “ clecoed” together and re-check during the riveting process. This was not done on the project I observed and a severely wing-heavy condition was the result.

There may be easier ways to do the repair. Cessna allows a certain amount of access holes that may help a lot. There may now be a replacement track that utilizes some parts of the original piece. ( Macfarlane ?). If there is it would eliminate about 2/3 of the labor involved.

Researching all options is always prudent.

 

[Bell206]

My recall : Defuel the aircraft.

FYI: you are recalling replacing the flap track rib assembly. Not the track or track plate. No reason to get into the fuel tank area/rear spar with just the track. While Cessna didn't publish a separate P/N for just a track in a few IPCs, they were procurable if you had the track P/N from tech support. If you couldn't find just an OEM track plate we would order an assembly and only use the track piece. McFarlane made it easier by duplicating that track piece as well as the Cessna SB upgrade on the flap rollers, flap arm issue, etc. But as I noted the McFarlane kit is the way to go.

Interesting an A&P would turn it down. That's a money maker.

Depends on your ops. If you're not set up to offer S/M or don't use those skills regularly it can easily go from bang to bust. Besides, with the amount of variances in Cessna flaps tracks half the battle can be just trying to figure out what flap track is needed. Unless that is you go magman's route and change only the flap track assemblies which takes you out of repair country and gets you closer to project territory when you start removing fuel cells.

 

[Magman]

That’s good news. It’s not really “my way” ( Sinatra?) but how I saw someone do it. Since this was 20 + of years ago I’m not sure what options existed then.

The further back you go the less information was readily shared. Thanks for the clarification on options.

 

[Dan Thomas]

Unless that is you go magman's route and change only the flap track assemblies which takes you out of repair country and gets you closer to project territory when you start removing fuel cells.

Fuel cells are a frequently ignored item. They are sitting on rubber strips (Cessna calls them 'bumpers") that age badly. They get hard and crack and crumble, and the glue holding them lets go so they work their way out from between the tank and the structure, and now we get chafing that eats through the tank. The tank hold-down straps have the same stuff on them, same problems.

Cessna wants those tanks inspected every three year or 1000 hours. I've had tank covers off that hadn't been off in 30 or more years, and the stuff we found resulted in expensive repairs and downtime. Not much savings in ignoring them for so long. One often finds the fuel sender gasket leaking. Sometimes the welds around the filler neck are cracked. The vent tube rubber hoses are all old and cracked up. Just getting the tank bay covers off can be troublesome, with the screws rusted into the anchor nuts, and now you risk spar and rib damage.

Normally, those bays get opened only when the tank starts leaking, and by that time you're looking at a lot of expense.

 

[I threw it on the ground]

Box aviation in Montgomery could do it. Half their guys are post military sheet metal so they don’t shy away

 

[Magman]

3 years/1000 hrs vs 30 years? I’ll bet most aircraft are in the latter category. I have NEVER had an owner request that the tank covers come off. Consequently removal can be a tedious job.Hardware can be an issue here.

As the typical cadmium plated screw enters the nut plate self locking feature the coating gets scraped off. Then you have a bare steel screw in what can be a humid environment. Then the end of the screw rusts away and removal is difficult. You can spray some from below and fog the area to protect the rest. Structural stainless screws or more frequent removal should make the task much easier.

It seems when that on the rare occasion that the covers are off that there is always some of the conditions Dan mentioned. Replacement tanks can be $$$.

 

[Gary Ward]

Fuel cells are a frequently ignored item. They are sitting on rubber strips (Cessna calls them 'bumpers") that age badly. They get hard and crack and crumble, and the glue holding them lets go so they work their way out from between the tank and the structure, and now we get chafing that eats through the tank. The tank hold-down straps have the same stuff on them, same problems.

Cessna wants those tanks inspected every three year or 1000 hours. I've had tank covers off that hadn't been off in 30 or more years, and the stuff we found resulted in expensive repairs and downtime. Not much savings in ignoring them for so long. One often finds the fuel sender gasket leaking. Sometimes the welds around the filler neck are cracked. The vent tube rubber hoses are all old and cracked up. Just getting the tank bay covers off can be troublesome, with the screws rusted into the anchor nuts, and now you risk spar and rib damage.

Normally, those bays get opened only when the tank starts leaking, and by that time you're looking at a lot of expense.

Been there, done that recently.

It has been 31 years since this was opened up. The tank was in a tornado and improperly repaired. It lasted 31 years but only 900 hrs of flying.
It got new everything, was very expensive even though we did our self's, my IA and I. It was a tough job.

Found a big mud daubers nest in the corner when I opened it up. Used contact cement on the rubber strips, they are not going anywhere. Butch Hartwig shop overhauled this tank, it fit like a glove. My original tank was not repairable.

Yes some 172 tanks are very rare and expensive now! Take care of the tanks you have! I have already been working on getting the LH tank cover screws loose for inspection and rubber strip replacement. Now I can get the screws out in 10 minutes to look down in there to inspect on the RH side. Getting the tank out to replace the rubber strips is a whole lot more work.

Stainless structural screws with anti seize on them. My IA suggested I paint them, which I think I will? Only thing is it may make it tougher for the next guy to get them out because I don't plan on taking them out any time soon! LOL

 

[Bell206]

I have NEVER had an owner request that the tank covers come off.

FYI: One of points I pushed on my owner-assist customers was to look over their aircraft beyond the inspection requirements. While I left the decision up to them I would give them the pros/cons of digging deep like pulling tank covers or tail feathers. Most would go along and when we were through digging they knew the entire condition of their aircraft and were better owners in the end. Did we find some major issues? Yes. But I had the support structure to get anything repaired which is why I could effectively recommend going that deep. In some cases due to aircraft type while I still would recommend this type review the con-side would have a higher price point should we discover a major issue.

 

[Dan Thomas]

FYI: One of points I pushed on my owner-assist customers was to look over their aircraft beyond the inspection requirements. While I left the decision up to them I would give them the pros/cons of digging deep like pulling tank covers or tail feathers.

Even the tank inspection is in the inspection requirements from Cessna, though not explicitly in the FARs, I think.

From the 172M manual:

 

[Dan Thomas]

Been there, done that recently.

It has been 31 years since this was opened up. The tank was in a tornado and improperly repaired. It lasted 31 years but only 900 hrs of flying.
It got new everything, was very expensive even though we did our self's, my IA and I. It was a tough job.

Found a big mud daubers nest in the corner when I opened it up. Used contact cement on the rubber strips, they are not going anywhere. Butch Hartwig shop overhauled this tank, it fit like a glove. My original tank was not repairable.

Yes some 172 tanks are very rare and expensive now! Take care of the tanks you have! I have already been working on getting the LH tank cover screws loose for inspection and rubber strip replacement. Now I can get the screws out in 10 minutes to look down in there to inspect on the RH side. Getting the tank out to replace the rubber strips is a whole lot more work.

Stainless structural screws with anti seize on them. My IA suggested I paint them, which I think I will? Only thing is it may make it tougher for the next guy to get them out because I don't plan on taking them out any time soon! LOL

Yup. One can see where the tank was chafing on the support and cover stiffener structure. That isn't a crack in the bottom support sheet, is it? Or is it just the edges of the 100LL stain? Was the stain from chafing damage or leaking gaskets? Or a cracked filler neck weld?

 

[Gary Ward]

Yup. One can see where the tank was chafing on the support and cover stiffener structure. That isn't a crack in the bottom support sheet, is it? Or is it just the edges of the 100LL stain? Was the stain from chafing damage or leaking gaskets? Or a cracked filler neck weld?

That is a fuel stain. Should have seen it before we used a shop vac to clean it out. Then I used mineral spirits to clean it up. Then I used adhesive remover to remove the old adhesive. It was spotless in there when I put it back together with fresh rubber.

The tank was not flat on the bottom and I could hear it "oil can" each time I filled it up. After replacing all vent and discharge hoses and the fuel sending unit gasket it still leaked a little. Until it leaked more, then I had to remove the cover. Then had to remove the tank and found a crack in the bottom from oil canning. Between rub marks, leaks around the seam that someone had already welded and stripped threads it was not feasible to repair. When I took the fittings out in order to remove the tank some of the threads were galled up on the brass fitting.

So what learned is if you hear your tank flexing while filling you are going to have a problem.

I removed all the old adhesive before glueing on the new rubber.

 

[Bell206]

Even the tank inspection is in the inspection requirements from Cessna, though not explicitly in the FARs, I think.

Not in the FARs but definitely in the Cessna program just as the SIDs are. Unfortunately on some older 100/200 series aircraft the costs to simply perform all the listed Cessna inspections are getting closer to the hull values. Talking with a friend in Australia where CASA made all Cessna SIDs mandatory for all 100/200 series aircraft, they have run head first into these high costs. If they were to follow suit here or up north I would bet a 1/3 of the current Cessna GA fleet would be grounded or scrapped. And while I agree following OEM recommendations is a definite plus I prefer to see those recommendations scheduled based on each specific aircraft vs a switch from a 43 Appx D annual straight into a full blown Cessna program. But as I've mentioned before this is purely driven by the owner regardless how I explain things to them. Thankfully the FAA way of doing business is much different than how CASA does things.

 

[Dan Thomas]

That is a fuel stain.

The tank was not flat on the bottom and I could hear it "oil can" each time I filled it up. After replacing all vent and discharge hoses and the fuel sending unit gasket it still leaked a little. Until it leaked more, then I had to remove the cover. Then had to remove the tank and found a crack in the bottom from oil canning. Between rub marks, leaks around the seam that someone had already welded and stripped threads it was not feasible to repair. When I took the fittings out in order to remove the tank some of the threads were galled up on the brass fitting.

So what learned is if you hear your tank flexing while filling you are going to have a problem.

Had a Citabria tank crack just like that, but on top. Right next to the stiffening bead. Pressing that bead into the metal work-hardens it a little and makes it more likely to crack.

Galled threads can be avoided by using Fuel Lube (EZ-Turn) as a thread sealant.

 

[Dan Thomas]

Unfortunately on some older 100/200 series aircraft the costs to simply perform all the listed Cessna inspections are getting closer to the hull values.

No different from a car or truck, really. There comes a time when the repairs outweigh its value. And there also comes a time when all those neglected items finally ground an airplane forever.

Yes, the US and Canada are still sane on the SID stuff. They will hopefully stay that way at least until too many start falling apart in flight.

 

[Magman]

All of the options ( tank, ladder , integral) have their issues. At least on a 172 the tanks are “easy?” to access. On the early Aero Commander Darters you first had to take the wing off. Then you drilled rivets to remove the Butt Rib to enable sliding the tank out for welding. AND their tanks seem to be noted for cracking.

Later s/n had access panels added I believe.

 

[Larry Korona]

As the owner working with an A&P I pulled my tanks in 2020 when I had a lot of time on my hands during the pandemic while I was on furlough. Took my hours of pure grunt work but was very happy to have done the job on my 1976 C172. Tanks have never been touched since the day the plane left the factory. Would have never done this job if I had to pay someone to do it.