Seat rails for a 79 M20J

[cliffy]

I agree that they are used in many places on Mooneys, the tail in particular, but are they used by Mooney on the seat rails?

 

 

[C-GHIJ]

I just finished mine.  Also replaced the stringers under the floor (I must have had some of Marauder's girlfriends up front) as we found a crack in 2 of them during the annual.  Wasn't that big of a deal.  Good practice as I am finishing up my AME-S licence (structural repair).  Personally, I would always use a solid rivet over a Cherry Max.  Had to use a bunch of different bucking bars to get into all the areas, but it is possible to do.

[DonMuncy]

Not being critical, but why would you prefer the solid rivet. Seems to me that the solid ones look a little neater (if in an exposed place), easier to replace if necessary, certainly cheaper per rivet, but a lot more trouble to install. Although I have never bucked a rivet on a plane. I did a couple in a leather harness arrangement by peening them on a metal surface with a ball peen hammer. 

1 hour ago, C-GHIJ said:

I just finished mine.  Also replaced the stringers under the floor (I must have had some of Marauder's girlfriends up front) as we found a crack in 2 of them during the annual.  Wasn't that big of a deal.  Good practice as I am finishing up my AME-S licence (structural repair).  Personally, I would always use a solid rivet over a Cherry Max.  Had to use a bunch of different bucking bars to get into all the areas, but it is possible to do.

 

[C-GHIJ]

The majority of the work in fabricating is getting the hole ready to rivet. It is the same for both cherry and solid rivets.  2 people working in harmony can drive/buck a rivet every 10 to 15 seconds or less when you are really going.  They make repair (removal) much easier than removing a Cherry rivet and at about a penny each compared to about 75 cents per cherry rivet it only makes cents. no pun intended.  The big advantage with a cherry rivet is that you can install it on your own and don't need a second person to help you.  You can be taught to drive and buck rivets in a few hours, it's not hard at all.

If you built a Mooney with just Cherry rivets, I bet it would weigh at least a 100 lbs more and probably cost twice as much.

[jetdriven]

The real advantage to a cherry Max is when you can't get a bucking bar behind the rivet. Such as all 56 holes in a 201 windshield retainer strip. 54 of them are -2s. But two are -6's.  

[kortopates]

5 hours ago, C-GHIJ said:

I just finished mine.  Also replaced the stringers under the floor (I must have had some of Marauder's girlfriends up front) as we found a crack in 2 of them during the annual.  Wasn't that big of a deal.  Good practice as I am finishing up my AME-S licence (structural repair).  Personally, I would always use a solid rivet over a Cherry Max.  Had to use a bunch of different bucking bars to get into all the areas, but it is possible to do.

Different models with different gear systems

[kortopates]

On 2/17/2016 at 2:07 PM, cliffy said:

I agree that they are used in many places on Mooneys, the tail in particular, but are they used by Mooney on the seat rails?

 

 

No, because the rails are put in as the floor is riveted together (some places with three layers of sheet metal) and before anything goes on under the floor (gear and gear actuator, brake lines, fuel selector and fuel lines etc etc)

Edited February 19, 2016 by kortopates

[cliffy]

The question was rhetorical :-)   Just because it's difficult doesn't mean it can't be done correctly with solid rivets

Another consideration is that blind rivets rely on friction to stay tight. How much flexing does the seat rail and floor get anytime the aircraft is moving (taxi or flight)? It's flexing all the time, with all the weight of passengers, working the friction areas of blind rivets loose if they are used on the rails.

What holds you in the seat in the event of a crash? The seat belt. 

What does the seat belt attach to? The seal structure.

What keeps the seat from pulling loose in a crash? The seat rails

Maybe it's not such a bad idea to follow the manufacturer and 43.13 on rivets when replacing seat rails. 

My shields are up

 

[Mikhail]

On 2/16/2016 at 10:16 PM, kortopates said:

Now that I have been through this job I can say because its such a huge job, I am very thankful I did all 4 seat rails. I'd hate to have gone to all that effort and only have done one side. My co-pilot side was actually more worn than the pilot side. I am also thankful I got the rails from the factory. I've heard horror stories on Cessna's pre-drilled rails not always lining up but the Mooney rails lined up really well for me. At the start I didn't realize to the extent that I was going to need to disassemble the gear as well as open up the bottom side skins by removing all the rivets all the way to the nose so I could peel back the skin enough to be able to get a bucking bar in there. Even after all that I still had to use a small number of cherry max rivets near the front of all of them but the finished product came out great. I also changed out all the deldrin rollers in the 2 seats (4 each), and re-webbed the seat belts and now the seats slide back and forth with ease and of course can't slip out of there holes. But don't even think twice about the cost of the rails, because its minuscule compared to labor to do the job. Thankfully I am A&P and only had to pay for the second person since every bucked rivet is a 2 person job. Plus with a pneumatic river squeezer the bottom side skins went back on very quickly - thankfully that was a one person job. 

Koropates,

I have to change my pilot inboard track and looking from the bottom it is impossible  to get to some location with bucking bar...

so I was thinking to use a Cherry Max , but are they approved by Mooney?

Thanks!

 

[jaylw314]

2 hours ago, Mikhail said:

Koropates,

I have to change my pilot inboard track and looking from the bottom it is impossible  to get to some location with bucking bar...

so I was thinking to use a Cherry Max , but are they approved by Mooney?

Thanks!

 

My understanding is CherryMax rivets are considered standard parts and meet the same specs as the equivalent MS rivet.

[kortopates]

15 hours ago, Mikhail said:

Koropates,

I have to change my pilot inboard track and looking from the bottom it is impossible  to get to some location with bucking bar...

so I was thinking to use a Cherry Max , but are they approved by Mooney?

Thanks!

 

Very few were needed but there is no other way to get a couple of the rivets in with the structure for the electric gear blocking access up in front of the rail The guidance is in AC-43.13-1B Section 4-57. See paragraphs f(3) and (6) in particular. They are 1.5-2x stronger than the rivets they are replacing. But if you want Mooney's specific endorsement you should email Stacey at Mooney.

Edited October 24, 2018 by kortopates

[M20F-1968]

You will want to get new one from the factory.  They are not that expensive, all things considered.  Last I look they were about $350 each.  They are order my model, and come predirilled abu you can request them to be un-drilled I believe.

John Breda

[Martin S.]

Evening gents,

anybody an idea if the factory is still selling/producing the seat rails. If no, are there any other companies selling these profiles new for Mooney aircraft? Anybody recently replaced them?

 

Greets from Germany,

 

Martin

[carusoam]

25 minutes ago, Martin S. said:

Evening gents,

anybody an idea if the factory is still selling/producing the seat rails. If no, are there any other companies selling these profiles new for Mooney aircraft? Anybody recently replaced them?

 

Greets from Germany,

 

Martin

Expect that the factory has them in stock somewhere… often at the MSC level…

They are still building and selling parts… may take a long time if not in stock…

 

Then there is the pre-flown variety… we have a few resources for that…

 

What has generated the request?  Broken or worn existing parts?

 

Not many get swapped out every year…

Biggest issue with the rails… is the wheels that ride on them…

PP thoughts only, not a mechanic…

Best regards,

-a-

[Guest]

1 hour ago, Martin S. said:

Evening gents,

anybody an idea if the factory is still selling/producing the seat rails. If no, are there any other companies selling these profiles new for Mooney aircraft? Anybody recently replaced them?

 

Greets from Germany,

 

Martin

It looks like you need p/n 340156-049 and 340156-051, two of each, assuming I have your serial number correct.  I’d have to contact the factory to verify inventory.  They showed only one of the first number .

Clarence 

[Martin S.]

Evening again, and thanks for the answers so far.
One of my rails seems to have a super thin crack. That’s why I was asking. Would you suggest replacing all rails, or just the cracked ones?


Sent from my iPhone using Tapatalk

[carusoam]

5 hours ago, Martin S. said:

Evening again, and thanks for the answers so far.
One of my rails seems to have a super thin crack. That’s why I was asking. Would you suggest replacing all rails, or just the cracked ones?


Sent from my iPhone using Tapatalk

Interesting…

got a pic of the crack?

 

You might be able to verify the cause of the crack, and see if something similar is going on with the other one…

They can be under load and see various levels of dirt… in their lifetime… something may have caused the crack to initiate and then propagate…

 

We haven’t seen many rail replacements going on around here… more discussions about how to add holes insitu than anything else…

Every now and then there are questions about changing them out because of challenges with getting the seat pins in place… but, that includes a fair amount of labor to execute getting access above and below the floor…

Typically cleaning, and tuning the holes, covers a lot of issues…

Many seats have lost their wheels over time… old roller materials broke and left a steel on aluminum wear issue….

Check the health of your seat wheels to make sure they are nice plastic (white Delrin? Not the old phenolic resin)

 

If you only have to replace the broken one… looks like Clarence has you covered…   

PP thoughts only, not a mechanic…

Best regards,

-a-

 

[Martin S.]

8 hours ago, carusoam said:

Interesting…

got a pic of the crack?

 

You might be able to verify the cause of the crack, and see if something similar is going on with the other one…

They can be under load and see various levels of dirt… in their lifetime… something may have caused the crack to initiate and then propagate…

 

We haven’t seen many rail replacements going on around here… more discussions about how to add holes insitu than anything else…

Every now and then there are questions about changing them out because of challenges with getting the seat pins in place… but, that includes a fair amount of labor to execute getting access above and below the floor…

Typically cleaning, and tuning the holes, covers a lot of issues…

Many seats have lost their wheels over time… old roller materials broke and left a steel on aluminum wear issue….

Check the health of your seat wheels to make sure they are nice plastic (white Delrin? Not the old phenolic resin)

 

If you only have to replace the broken one… looks like Clarence has you covered…   

PP thoughts only, not a mechanic…

Best regards,

-a-

 

Yes - took a picture. Crack does not go through the entire cross-section of the profile. Question is whether this justifies a replacement of the track?

Greets,

Martin

 

[EricJ]

Get a macro borescope and see if you can see whether that crack goes very far into the hole.    You might be able to get some dye penetrant in there but it'd probably be tricky.

If new rails aren't available and the crack isn't too deep you could potentially grind off the crack and replace it, maybe with some some new metal deposition from a welder if the material is suitable (I'm guessing that's steel of some kind).

[Guest]

The AD on Cessna seat rails allows flight with cracks.

Clarence

[carusoam]

Hmmmm….

Kind of a summary list of things to consider… in case you haven’t thought of them yourself…  

1) cracks have a tendency to propagate….

2) What would happen if the part broke in half along the crack?

3) Could  the seat rail move?

4) typically cracks can be stop drilled…

5) The dye penetrant may give a hint of where the rest of the crack has already propagated….

6) Imagine a method of stop drilling this crack in place….

7) What initiated the crack? (Looks like it may have started at the machined hole…. )

8) Look at how many rivets hold the rail in place…

9) How much force is applied to the each rail… under all conditions?

10) During an accident the seat rail is in charge of holding you back away from the instrument panel…

 

PP thoughts and summary of the input above… not a mechanic…

Best regards,

-a-

[Martin S.]

Thanks everybody - really appreciate all your input. Found it interesting to see that the Cessna AD indeed tolerates more than one crack in the rails. 

Greets,

 

Martin

Edited March 22, 2022 by Martin S.

[A64Pilot]

23 hours ago, M20Doc said:

The AD on Cessna seat rails allows flight with cracks.

Clarence

I know this isn’t a Cessna, but that AD has been out so long and so throughly researched by so many that I would use it as a reference for our Mooney, and I’d bet most FAA inspectors would agree.

Having said that I’d be concerned if the cracked hole is the one that holds the seat in place when your flying, if you lock your seat in another hole, I wouldn’t worry myself.

Just my opinion

[Andy95W]

2 hours ago, A64Pilot said:

I know this isn’t a Cessna, but that AD has been out so long and so throughly researched by so many that I would use it as a reference for our Mooney, and I’d bet most FAA inspectors would agree.

You’re willing to use the Cessna standards for a Mooney seat rail, even though there is no published procedure to do so, but you’re not willing to do a ring flush on an engine cylinder because there isn’t a published procedure.

[A64Pilot]

14 hours ago, Andy95W said:

You’re willing to use the Cessna standards for a Mooney seat rail, even though there is no published procedure to do so, but you’re not willing to do a ring flush on an engine cylinder because there isn’t a published procedure.

Sure, because Cessna is an aircraft, and there are published procedures, and of course the seat tracks are very similar

Show me say a ring flush procedure for a Franklin or other aircraft engine and I’d say you have at least some kind of applicable data, but without some kind of approved data what do you have to show this procedure is safe? Very often when there exist no inspection criteria, it’s logical to use procedures for nearly identical assemblies on other aircraft that have established criteria.

Mike Bush says you don’t even need a mechanic to do this ring flush, a pilot is allowed, so what do you care what I think?

Ref seat tracks again the FAA has taken a recent position of if there are no damage criteria in a structures repair manual, that means no damage is allowed.

I went through that argument with an FAA inspector about leading edge damage, we didn’t have a structure repair manual, and I wasn’t going down that road either, my position was 43.13 is an excellent manual.

On edit, think of it this way, gummed / carboned up rings is NOT normal for a healthy cylinder, it is however normal for a cylinder with excessive blow by, so cleaning out the rings doesn’t fix whatever is wrong, whatever condition that gummed up the rings is still there.

However as an example having to clean spark plugs is normal, it’s a normal operating condition for plugs to carbon up, so ther are approved procedures for cleaning spark plugs.

My primary concern with a ring flush is that nothing is done to investigate and correct whatever is causing the rings to stick, if you don’t correct the condition, why won’t they stick again? Maybe when your in a mountain wave trying to get over the Rockies or other in opportune time?

Edited March 23, 2022 by A64Pilot