Can you add holes to a seat track?

JScarry

JScarry

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My 6' 7" nephew wants to learn to fly and he barely fits in my Cherokee 140. If I could move the seat back two more holes I think it would be perfect.

Is it legal to drill two more holes in a seat track? If so would it be a minor alteration?
 
IMHO,, that would be a modification to the type design.
 
removing metal from your airplane is rarely a good idea.
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We drilled extra holes in my Cherokee 180 seat rails and it was signed off on by the AP/IA. Now, whether it was legal or not, well, he thought so and signed it off.
 
Phone books—or a seat cushion—do help with leg room if you have the head room. They give you a couple of extra inches of leg extension. They work for me but he’s a bit taller than me.
 
Tom-D said:
IMHO,, that would be a modification to the type design.
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Agree. I don't know about the Piper, but the Cessna seat rails are part of the aircraft's structure, according to Cessna engineers. More holes in the wrong places, or badly drilled holes, could weaken the airframe.
 
Dan Thomas said:
Agree. I don't know about the Piper, but the Cessna seat rails are part of the aircraft's structure, according to Cessna engineers. More holes in the wrong places, or badly drilled holes, could weaken the airframe.
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Piper seat tracks are not as flimsy as Cessna, but it still has W&B issues, the arm and moment will not reflect the Pilots operating hand book or the type certificate.
This is one of those things that probably wouldn't make a hoot until some Piper guru spotted it.
 
EdFred said:
We drilled extra holes in my Cherokee 180 seat rails and it was signed off on by the AP/IA. Now, whether it was legal or not, well, he thought so and signed it off.
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If your IA was good with it and signed it off then it’s a minor alteration and 100% legal. I think some of you guys overthink this stuff. Is drilling a couple extra holes in a seat rail (if done properly) really going to affect the structural integrity, even in a crash? Common sense and logic says, probably not.
 
NotarPilot said:
If your IA was good with it and signed it off then it’s a minor alteration and 100% legal. I think some of you guys overthink this stuff. Is drilling a couple extra holes in a seat rail (if done properly) really going to affect the structural integrity, even in a crash? Common sense and logic says, probably not.
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NTSB would beg the differ. Every thing becomes a big deal to NTSB. A&P-s have gone away for a lot less.
 
Tom-D said:
NTSB would beg the differ. Every thing becomes a big deal to NTSB. A&P-s have gone away for a lot less.
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Not to sound like a smart as here but I’d sincerely like to read some examples for the purpose of educating myself. I’ve heard of A&Ps going away to prison for working on jack screws on MD-80s or falsifying W&B computations on S-61 helicopters that killed 9 people but never for something as minor as drilling a hole in a seat rail, but hey, I could be wrong.
 
NotarPilot said:
If your IA was good with it and signed it off then it’s a minor alteration and 100% legal. I think some of you guys overthink this stuff. Is drilling a couple extra holes in a seat rail (if done properly) really going to affect the structural integrity, even in a crash? Common sense and logic says, probably not.
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Strongly suggest you re-think your position on this -- "drilling a couple holes in a seat rail" is a big deal, not something done on a whim, and would require field approval. Can it affect the structural integrity of the aircraft? Absolutely. Even in a crash? ... ABSOLUTELY!
 
Ryan F. said:
Strongly suggest you re-think your position on this -- "drilling a couple holes in a seat rail" is a big deal, not something done on a whim, and would require field approval. Can it affect the structural integrity of the aircraft? Absolutely. Even in a crash? ... ABSOLUTELY!
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On a Cherokee? Nope. Non structural.
 
Non-structural? It is the critical means of attachment of the pilots seat to the aircraft. Of course it is structural.....
 
Lndwarrior said:
Non-structural? It is the critical means of attachment of the pilots seat to the aircraft. Of course it is structural.....
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Not in the way all the rest of us are talking about it. That's like saying my armrest is structural.
 
First thing I'd do is contact the OEM and ask. If no then pose the question to a third party DER.
 
Get a Mooney... you know you want the extra speed anyway. And if there's a wife involved, you're doing it for the nephew ;)
 
EdFred said:
Not in the way all the rest of us are talking about it. That's like saying my armrest is structural.
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No, it's not. An armrest is not designed to save your life in a crash. The seat attachment is.
 
Lndwarrior said:
No, it's not. An armrest is not designed to save your life in a crash. The seat attachment is.
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Drilling an extra hole or 2 with proper spacing will have 0 effect on the seat rail in a Cherokee in a crash. It is NOT a structural item the way others are. I used to work in metals, I *may* actually know what I'm talking about. You know what's going to fail first on the Cherokee seat rail system? It isn't going to be the rail even with the extra holes.
 
EdFred said:
Drilling an extra hole or 2 with proper spacing will have 0 effect on the seat rail in a Cherokee in a crash. It is NOT a structural item the way others are. I used to work in metals, I *may* actually know what I'm talking about. You know what's going to fail first on the Cherokee seat rail system? It isn't going to be the rail even with the extra holes.
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Modifying a part would be the same as installing a non PMAed part.
 
NotarPilot said:
Not to sound like a smart as here but I’d sincerely like to read some examples for the purpose of educating myself. I’ve heard of A&Ps going away to prison for working on jack screws on MD-80s or falsifying W&B computations on S-61 helicopters that killed 9 people but never for something as minor as drilling a hole in a seat rail, but hey, I could be wrong.
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Hey do I know you? I did the recovery on that one with the Lama.
 
Sorry, you're not going to convince me that an IA sign-off is sufficient to modify a seat rail. In my opinion such a modification renders the aircraft unairworthy until legal rails are re-installed.
 
In the middle of two existing holes maybe, maybe not, depending on the structural argument, but past the last one seems like a definite no, since it would invalidate the certified weight and balance numbers as tom mentioned.
 
Ryan F. said:
Sorry, you're not going to convince me that an IA sign-off is sufficient to modify a seat rail. In my opinion such a modification renders the aircraft unairworthy until legal rails are re-installed.
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ya but......9 outta 10 IA's will never notice that extra hole....and....what difference does it make? :D
 
Salty said:
In the middle of two existing holes maybe, maybe not, depending on the structural argument, but past the last one seems like a definite no, since it would invalidate the certified weight and balance numbers as tom mentioned.
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In the middle would be a problem because now the amount of metal between holes is not sufficient. At the end you wouldn't have issues. And since Cherokees are prone to forward CG issues, moving it back actually puts you in a better spot CG wise. And if one looks close at later PA28 W&B they actually give the different arms for different holes, so you can even calculate the new ones. As long as the distance between the last hole and the edge of the seat rail isn't less than what it is between holes there's 0 problem as long as the rail didn't narrow down where you are putting the hole.
 
EdFred said:
In the middle would be a problem because now the amount of metal between holes is not sufficient. At the end you wouldn't have issues. And since Cherokees are prone to forward CG issues, moving it back actually puts you in a better spot CG wise. And if one looks close at later PA28 W&B they actually give the different arms for different holes, so you can even calculate the new ones. As long as the distance between the last hole and the edge of the seat rail isn't less than what it is between holes there's 0 problem as long as the rail didn't narrow down where you are putting the hole.
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so....where are you drilling?

s-l400.jpg
7a1c08cdecf357e60edacbdc35c5ae28_1024x1024@2x.jpg
 
EdFred said:
In the middle would be a problem because now the amount of metal between holes is not sufficient. At the end you wouldn't have issues. And since Cherokees are prone to forward CG issues, moving it back actually puts you in a better spot CG wise. And if one looks close at later PA28 W&B they actually give the different arms for different holes, so you can even calculate the new ones. As long as the distance between the last hole and the edge of the seat rail isn't less than what it is between holes there's 0 problem as long as the rail didn't narrow down where you are putting the hole.
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Can you do the math? Sure.

Seems like the faa would want to see the “engineering” at a minimum.
 
Six....those were not the rails the seat attached to that I had in my PA28. At least not from what I recall.
 
On those we put one or two more holes at the back of the line of 9. Its been 15 years, so I don't recall if we had to do something at the back to insure the seat didn't slide out of the rail. I think there was still clearance, and nothing at the rear had to be modified, but like I said, 15 years. Though I don't remember there being 9 holes. Maybe those rails have been modified already.
 
Minor, but the W&B section should be updated.
These aren’t 25G rated seats, they’ll probably deform before the rails anyway.


Tom
 
Tom-D said:
NTSB would beg the differ. Every thing becomes a big deal to NTSB. A&P-s have gone away for a lot less.
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"gone away" typically refers to jail time.

So what A&P's has served time for an illegal modification that is (a lot) less than drilling an additional hole in a seat rail?
 
IF you can find someone properly credentialed to do it and sign off on it it can be done. I have an A&P and agree with @Tom-D but if you find someone like @EdFred knows go for it... not your certificate. Just have to trust the guy drilling and signing that the seat locks and the rail is still to standard for structural purposes.
 
For those who care, most A&Ps loose their privileges because of falsifying paper work.
 
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