Broken Seat

[Runtoeat]

If you haven't inspected your seats recently, I would HIGHLY recomment that you do this. This last week I have seen a CTLS and a CTSW with cracks in the structure. The cracks were located on the bottom of the seat structure, where the seat bottom transitions into the seat back. The seats must be taken out and the cover may have to be pulled up a few inches to inspect this area. At one time, I read where one must keep the support strap tensioned to keep the seats off the floor but could not find this. If someone runs across this, please let me know where you found it. This is something I check frequently on my plane.

[N78BZ]

If you haven't inspected your seats recently, I would HIGHLY recomment that you do this. This last week I have seen a CTLS and a CTSW with cracks in the structure. The cracks were located on the bottom of the seat structure, where the seat bottom transitions into the seat back. The seats must be taken out and the cover may have to be pulled up a few inches to inspect this area. At one time, I read where one must keep the support strap tensioned to keep the seats off the floor but could not find this. If someone runs across this, please let me know where you found it. This is something I check frequently on my plane.

 

 

I had to have the pilot seat repaired during my annual.

[Jim]

If you haven't inspected your seats recently, I would HIGHLY recomment that you do this. This last week I have seen a CTLS and a CTSW with cracks in the structure. The cracks were located on the bottom of the seat structure, where the seat bottom transitions into the seat back. The seats must be taken out and the cover may have to be pulled up a few inches to inspect this area. At one time, I read where one must keep the support strap tensioned to keep the seats off the floor but could not find this. If someone runs across this, please let me know where you found it. This is something I check frequently on my plane.

 

When I took delivery of my CTSW, I was cautioned to always position the back strap so that it supported the rear of the seat and kept it well away from the bulkhead. It has been talked about in the forums, but I don't have a source either.

[airhound]

What is the seat bottom made of?

[Roger Lee]

Hi Guys,

 

The seats should be tensioned with the strap to not rest against the bulkhead. It should have a little space. If it rest against the bulkhead I has a fulcrum point and breaks in the middle. The seats can be repaired with fiberglass. Remember when you do this that the strength is not in the epoxy, but in the layers of fiberglass and any excessive epoxy should be removed.

[Runtoeat]

What is the seat bottom made of?

 

I'm guessing that there are at least 2 types of cloth in the seats. There is what appears to be standard clear glass cloth in the majority of the seat but there is also a yellow colored coarsly woven soft cloth that is captured in the epoxy which runs in 3" wide strips down each side of the seat with occasional cross pieces too. I'm guessing that this is kevlar? If this is kevlar, it means that there are very high loads because I have seen this material ripped almost in half. Roger and Jim are right that the seats cannot rest against the bulkhead. This causes the seat to be wedged between the bulkhead and the front connection and to "fold" on itself when weight is applied. All of this load is concentrated at the area where the seat bottom curves up into the seat back and it appears to pull apart both the glass cloth and the yellow (kevlar?) cloth.

 

Roger, your point about using too much resin is well taken. Recently, I have leared about "less is more" when it comes to how much resin is used. I'm sure that the composite classes being offered woud be real interesting.

[airhound]

Is it the seat back that normally breaks if not tensioned correctly? How about the seat bottom? What would crack that....a knee or big butt??

[Runtoeat]

Is it the seat back that normally breaks if not tensioned correctly? How about the seat bottom? What would crack that....a knee or big butt??

 

Doug, the seat comes out easily and it is best to just take it out to inspect it. Remove the support strap out of the bracket on the back of the seat, pull the lanyard to release the front pins and out it comes. It is a good idea to do this occasionally. Look at the bend where the bottom of the seat transitions to the back. Picture holding the top edge of the seat with one hand and the bottom edge of the seat with your other hand. Push your hands together and try to fold the top edge of the seat back to the front edge of the seat bottom. This is what happens each time you sit in the seat. It appears to me that the high loads occur in the outside layer of the seat structure in the area of the bend. All cracking I have seen have occured in the seat bottom going into the bend area. I am thinking that it might have been better to provide some sort of stiff foam pad btween the seat and the floor at the bend area to support it instead of relying on the strap support. Then again, the seat is designed to absorb vertical loads encountered during a impact with the ground and this strap system may absorb energy better than a semi-rigid support of the seat?

 

Weight woud seem to be a factor in regards to a broken seat but I have seen both seats broken in a CTLS and the owner and his wife are not heavy people and the seats have never been abused or subjected to hard landings.

[airhound]

Runtoeat,

 

Thank you for the detailed explanation and will check to find out why the kreaking. Have a nice weekend!