Comanche carpets - underneath the seat rails,or around them?

[Malcolm Dickinson]

My 1968 Comanche came to me with a one-piece carpet that was laid flat on the floor and then the seat rails for the front seats were bolted through the carpet into the floor.

I took it to the same mechanic for 10 annual inspections and he always put it back together the same way at the end of the inspection.

Then last time I needed an annual, my regular mechanic was too busy so I took it to a shop in a neighboring state. I chose this shop because a fellow Comanche owner said they did good work and also the shop owner owns a Comanche himself.

When I got the plane back after the annual, the mechanic had cut slots in the carpet so that the seat tracks were bolted flush against the floor (no carpet sandwiched between the seat tracks and the floor). He said that he had corrected this problem and that seat rails must always be flush against the floor. He sounded 100% certain... he's a lifelong A&P, and a Comanche owner to boot, so he should know, right?

Ever since then, the carpet, once cut, has been flipping up, bunching up, won't stay flat, etc. It looks awful.

This year I am going to a third shop for my annual. I asked the mechanic at this shop - also highly experienced, also a Comanche owner - and he said "that's ridiculous. All Comanches have the carpet sandwiched between the seat tracks and the floor. I maintain ten Comanches, and they are all configured that way." He, too, sounded 100% certain.

So I thought if these two A&Ps don't agree, I'll call the ICS and get the real answer. Placed a call to Bill Creech, our technical advisor. Bill tells me that the carpet may NOT be sandwiched between the seat tracks and the floor; the tracks must sit flush on the floor. He mentions that there is even a supplier that will pre-cut the holes in the carpet so that it will fit neatly around the seat tracks.

So there you have it folks - 2 highly knowledgeable A&Ps say the carpet belongs sandwiched under the seat tracks, and one A&P plus a highly knowledgeable ICS person say the carpet must be cut to go around the seat tracks, and must not come between the tracks and the floor.

The score is now tied! How do I find the REAL answer?!

Thanks,
Malcolm

[Jim Worley]

FWIW - My 61 250 has the rails on top of the carpet. At my last annual, my very experienced A&P, commented that the rails should not be on top of the carpet. She, however, went ahead and signed off on the annual because I told her I would take care of it when I put it back together after the panel upgrade. I would like to know the answer too. I would much rather not cut holes in the carpet.

Jim

[md11flyer]

Malcolm:

The problem with the rails over the carpet is that you will get movement between the tracks and the floor ribs that the tracks are attached too.
The tracks will move ever so slightly causing the ribs below the floor to crack. When the rails are secured to the floor boards directly you don't get this movement.
After I bought my twin comnache we did a very thorough inspection and in the process we found 3 cracks in three floor ribs. Not big cracks, but in any event they where there and had to be fixed.
My mechanic said the cracks developed because of this movement over the years that the carpet was placed under the rails.

Airtex sells carpet for our comanches for around 550 dollars. This carpet is cut with the tracks cut out and they stitch around the holes so the carpet doesn't unravel.

Goodluck,

Gary

[N3322G]

FWIW. 41 years of rails on carpet in Twin coming up on 6,000TT. No problems, no cracks.

As for a mechanic, any mechanic, who alters my aircraft without discussing it with me - not one I'd do business with again.

[David Pyle]

This is an old issue and not one that "experienced" Comanche A&Ps agree. I suspect that inspection of the original Piper installation will show that the seat tracks are NOT on top of carpet. I further suspect that when interiors are redone those that do the work take the easy way. I think Airtex does it the right way...track cut outs and binding them. Unbound seat movement can get hung up on the carpet edges. Trust Bill Creech. He knows all and sees all.

[Don Nelson]

I agree with Bill, David, and others who say the carpet should not sandwich under the rails. No way to not have some movement of the rail, if so. Good way to have the screws shear off in a crash, where they otherwise might not.
Whether the factory did it that way or not, it's wrong, IMO!

Both my 250's were purchased with the carpets cut and edge bound to fit around the rails.
Don

[Jody Brausch]

Sky Harbour installed a new interior in my PA30. I chose them because of their excellent reputation, and knowledge of the aircraft restoration process. They discussed every detail of the restoration with me, including the carpet installation, and provided their perspective about this very subject. Essentially, they installed the carpet around the seat rails for a whole host of reasons,including the possibility of cracked ribs as a result of a rail shifting if placed under a load. Sky Harbour's solution was to use several custom cut pieces of carpet, attached together with velcro fasteners, allowing the mechanic to easily remove any particular piece, or the entire carpet, to access things like wing spars, floor panels, access panels, etc. It looks great, its functional, it goes back together easily after the annual, and unless you knew the carpet was pieced together in this way, you couldn't tell the difference. As an added benefit, the seat rollers don't bind quite as much as they used to.

[smith-ja]

For what it's worth, my twin, 8662Y, was delivered by Piper, in March 1969, with the "Palm Beach" interior. The Piper "Gold" carpet was covered by bubble wrap
and the rails were on top of it. It stayed that way until 1984 when we decided to change the color scheme. The floor panels have been removed many times for maintence by me, personally. The rail screws are the originals.

Jim Smith
ICS 05017

[tomburke1]

As far as I know, all the Comanches were made with the carpet between the rails and the floorboards.

Maurice always said that it was better to cut out the carpet and mount the rails directly to the floor boards. I changed mine when I redid the interrior. If you decide to do that remember that the existing bolts need to be changed to a shorter set so the shoulder does not strip the anchor nuts that they screw into.

I too find fault with a mechanic that does not discuss a change such as that with me before doing it. It was originally installed by Piper that way and I have never seen a SB, or AD saying that you have to do it differently so I can't see an IA refusing to sign off an airplane with the carpet between the floor and the rail.

[Ray B]

Those of us old enough to remember "New" Comanches can recall that the seat rails were indeed on top of the carpet, but those carpets were quite thin. When an old friend of mine bought his new 1959 250 the rails were on top of the carpet from the factory. Years later when he replaced the carpet with new plush thick stuff he had rail cutouts in the carpet and had the rails screwed directly to the floor. The screws were not replaced with shorter ones as the original compressed carpet was probable no more than a 1/16" thick if that. My 51 year old 250 has the rails on top of lord knows how many replaced carpets and at 5.000 hours no cracks. So go figure, maybe 6659P has never had a 300 lb. owner! Our shop has fixed two seats in cherokee sixes due to 300+ lb. owner/pilots. Another reason to eat your veggies. Ray B

[9089P]

It is much easier to blame Piper for poor installation than yourself for a poor diet.

Don

[skipsouthernsky]

To all,

My two cents......Tom is correct when he says that Maurice always said to put the seat rails directly on the floor and not have the carpet between the rails and the floor. Ray, as far as I know, is also correct in saying that Piper put carpet between the rails and the floor, but the carpet was not the high pile, plush carpet that some have since used. My understanding about this issue is that by having the carpet, especially the plush carpet, between the rails and the floor, is that the rails will tend to develope slight indentions where the seat normally sits, especially if the same pilot or co-pilot positions the seat at the same place every time. Think about it, the carpet will allow the rail to be slightly elevated and by applying pressure at the same four places every time, then the rail will be allowed to bend slightly down. Over time, with these slight indentations, the seat will tend to have resistance at these indentations when sliding. I guess the real question that should be asked, "Do you want your seat tracks to have theses indentations or not?" Murice believed in keeping the seat tracks straight and so do I. Hence, no carpet between the rails and the floor.

As far as the carpet causing cracking of the rib understructure in the cockpit area, I'm not sure there is a real cause and effect here. Although some Comanches have developed cracks in ribs in that area, and I'm sure some of those Comanches had carpet between the rails and the floor, I doubt that the carpet is the real cause. Anyway, just because your Comanche currently has carpet between or not, doesn't necessarily mean it has always been that way. Remember we are talking about airplanes that are 50 years old and gone through countless owners.

There are pros and cons either way you go. As far as I know there is no regulatory reason why you have to choose one or the other. Just a preference of whether you like straight rails vs. indented rails, and whether you like the trade-off of well planted carpet vs. carpet that tends to fray around the edges of the seat tracks. Your call.

Sincerely,
Skip Dykema

[tomburke1]

As hard an alloy that those rails are made of, I find it questionable as to whether the force exerted on them would cause an indentation.

Whether or not you decide to install the rails direcrtly to the floor, or with the carpet between the rails and the floor, jut remember that the removal of the carpet from between the rail and the floor board might create a poroblem with the shoulder bolts that secure the rails to the anchor nuts under the floor.

[Mark Anderson]

I just replaced my carpet with the Airtex carpet. I did not come with the slits for the seats. I removed the old carpet and took both of them to a upholstery shop and had them use the old one for a pattern and sew a trim strip around the edges. I just found it easier to go this way than unscrewing the seat rails. The hardest part for me was trying to tuck the edges under the side panels, very tight , without Removing them.

[RLF]

I just received carpet from Airtex and called them with this very question. Their response was to put the carpet between the floor and rails. I was a bit surprised by that, but that's what I did!