Engineering Question

[md11flyer]

Hello:
Does any one know if the seat rails are structural members?
My question is regarding how the carpet is laid. I am renewing the carpet and it has always been installed under the seat rails.
But if the seat rails are structural, I am almost certain they can not do their job being placed above the relatively thick carpet.

I know it is the seat belts, tied to the airframe, that take the occupant loads during a sudden deceleration. The seats themselves as with the rear kid seats are just secured for obvious reasons.

But if the rails provide a "spar cap" effect then I would assume that the engineers would not condone installing the carpet under the rails.

Anybody with expertise with this?

Thanks,

Gary

[Zach Grant L1011jock]

Seat rails are not structural to the airframe. With that said they do tie into the structure of the airframe with 4 long machine screws that run through nut plates on the flanges of the frames under the floorboards. Original Piper factory installed carpet was under the seat rails. Many believe this was why some rames were found cracked. I think that it can be done either way. The trick is to make sure the frames do lign up when you put the screws in, and make sure the screws are drawn down fully, pulling the frame up to the floorboard, and subsequantly compressing the carpet beneath the seatrail. Retorque periodically as the carpet compresses and you should be fine. Also make sure your tracks and rollers are lubricated properly. Use a dry teflon lube, or else the oil residue will attact all of the grime on the floor and nothing will slide freely.
-Zach

[md11flyer]

Thanks Zach:

I purchased some new surplus delux wool carpet (excess from a corporate
interior redo) and it does not compress very easily. I will see how it snugs up under the seat rails.
Otherwise I will trim the carpet around the seat rails and use velcro tape to secure the carpet to the floor.

Gary

[Zach Grant L1011jock]

Gary,
That would probably be a better option, to trim, than not, based on the carpet you are using.
-Zach

[Jay]

Gary:

My airplane has wool carpet, trimmed around the seat rails. It looks nice and it's easy to get the carpet up for access to wiring, etc. without having to remove the rails.

Jay

[Ben Ayalon]

This subject came up in the past and was discussed at length, the consensus was that it is much better to fit the rails directly on top of the floors and to cut the carpet. The reason for it is that if the rails are on top of the carpet the bolts that holds the rails can flex with the anchors below when you move the seat or on it. My aircraft had the rails on top and the seats attachments below the floor were broken.

Ben

[Chuck Lee]

[Chris Kuyoth]

[ics-12766]

[T210DRVR]

[md11flyer]

[9089P]