Installing the Pilot / Co-Pilot Seats
As you may know the seat rails on most Cessna aircraft have an AD, 87-20-03 that requires inspection of the rails and seats at every hundred hour or annual inspection. You may also know that this is because these original rails were prone to coming unlatched and usually on climb out which is not a good thing.
The new style rails that came when Cessna started the line back up again in 1997 are much different. The pin mechanism acutally goes through the side of the rails and cannot slip. With any luck these rails would pick up the same (or close to) mounting holes that the original rails used making the swap a "non-structural" modification.
Here is a picture of the original seat rails. Note that they are riveted to the aircraft structure. The new style rails use AN structural bolts which makes a replacement job much easier.
http://mansfieldlanding.com/forum/photos/1972_cessna_172l_restoration_n19662/picture164.aspx
The original rails were removed and the structure inspected for corrosion or cracking. We then cleaned the area in preperation for primer and the new rails.
http://mansfieldlanding.com/forum/photos/1972_cessna_172l_restoration_n19662/picture165.aspx
The front of the rails had a stiffner that was riveted with the rails from the underside. This helps stiffen the area between the front and middle stringer. We used flat head rivets and installed these stiffners back to their original position. This would then allow us to bolt the new rails instead of using rivets.
http://mansfieldlanding.com/forum/photos/1972_cessna_172l_restoration_n19662/picture166.aspx
The new rails were laid in and the bolt pattern matched the original area where the rivets hit the aircraft structure. They are not as wide as the original rails but much stronger. We picked up one side of the original rivet pattern and made new holes to align up with the bolts on the other side of the new rails.
Here are the new rails installed in the aircraft. We did not need to modify the rails at all, and they picked up the basic pattern of the original rails.
http://mansfieldlanding.com/forum/photos/1972_cessna_172l_restoration_n19662/picture167.aspx
All in all the modification is fairly easy, makes a much better rail system (assume that is why Cesssna designed them) and they should be approved as an "alternate" means of compliance against the original AD eliminating the need for inspections.
Here are a couple of pictures with the seats installed. They look and feel great!
http://mansfieldlanding.com/forum/photos/1972_cessna_172l_restoration_n19662/picture168.aspx
http://mansfieldlanding.com/forum/photos/1972_cessna_172l_restoration_n19662/picture169.aspx