Back Seat Attachment Question

[DaveF]

At my mechanic's insistence, we removed the side brackets and did the job the "right" way.

Here's the RH bracket removed:

Both brackets with new nutplates and some ZnCr applied:

Reinstalled:

Aft mounting location with doubler plate. We pulled Cherrymax rivets in the aft three locations. The two screws hold a retainer with the new nutplate.

The nutplate retainer from below:

[4-Shipp]

Quick update on replacing the rear seat attach bolt nut plate.

I used a AN366F-428A nut plate. I layed out the center lines on the rivets holding the doubler in place as shown in the earlier pictures. I drilled two holes an inch apart on line corresponding to the original nut plate. I then drilled through the doubler and the floor to remove the rivets holding the original nut plate in place. The old nut plate popped right off. The new plate was riveted in place. It was easy to access the back of the rivets through the inspection hole. The whole process took less than 30 minutes. Piece of cake!

[Indopilot]

Just an observation, While your mechanic was doing it the " Right " way did he insist on doing a burn test on your cabin insulation at the same time? Sorry just had to stir the pot.

[junkyard_kahrs]

Seemed to be the best thread to add this question-

Am I doing this right? The parts manual illustrates a bushing around the bolt, but with the proper sized bolt I don't see how one could fit in there.

Prepped seat frames

[JohnNielsen]

I found my seats much more comfortable and lighter when I removed all the steel spring suspension and replaced it with control surface fabric, then had Aircraft Sport Seating in AK make me modern multi layer pads and covers to slip over the frames. John.

[bagarre]

Mine don't have a bushing in there either. Just the bolt.

+1 on getting rid of the steel springs. Makes for a more comfortable seat. I'm in the process of doing it now. Just need a few warm days to make my unheated garage tolerable.

[ghostflyer]

Personally I would be very hesitate in changing a seat design. Cessna designs and builds seats to take a certain G load and those springs or a combination of springs creat the seat loads that are to be for a comfort factor but are there also to absorb loads eg for heavy landings. I have seen the results and reports of somebody that modified the seats of a early cessna 172 seats and made a pan of Celonite glued around tubular frame . On the heavy landing the glue let go and the 2 persons on board had their body submarines into the seat frame causing extreme back injuries . Yes it was a very heavy landing ,1gear torn out of the aircraft ,nose wheel assembly torn out . The National Transport Safety Board was very critical of the mods done to the seats

[GAHorn]

Personally I would be very hesitate in changing a seat design. Cessna designs and builds seats to take a certain G load and those springs or a combination of springs creat the seat loads that are to be for a comfort factor but are there also to absorb loads eg for heavy landings. I have seen the results and reports of somebody that modified the seats of a early cessna 172 seats and made a pan of Celonite glued around tubular frame . On the heavy landing the glue let go and the 2 persons on board had their body submarines into the seat frame causing extreme back injuries . Yes it was a very heavy landing ,1gear torn out of the aircraft ,nose wheel assembly torn out . The National Transport Safety Board was very critical of the mods done to the seats

Good words. If you have your seats modified be careful who does it, and confirm their documentation will allow legal reinstallation into a certificated airplane. (May require Form 337/STC depending upon the amount of modification.) Subsequent sale relicensing of the airplane may be complicated.

[junkyard_kahrs]

The rear seat with the new foam. Additional, thinner foam will wrap the front skirt before covering.

Rear seat with new foam & canvas

New canvas material installed (from Airtex).

New canvas, detail

Francisco (Compton KCPM) explains his plans for the completion of the seat.

Francisco explains next steps

An example of Francisco's completed work in another C170. These seats have altered, higher seat backs with a more square profile. Mine will adhere to the original countour.

Another 170 completed by Francisco

[reecewallace]

George, there was an article written by C170 member John Gileno #1776 CT describing a method of replacing the nutplates being discussed here that does not require drilling out rivets or cutting holes in the bracket. I have a printed copy of the article that I would be glad to send to someone or to you to post on the forum. I don't know how to do so myself or I would do the posting. I gave a copy to the IA who was doing my mechanical work several years ago and he used the method described to replace the two nutplates in my plane. I don't recall if the article was in the 170 News or was on this forum, but possibly others reading this will recall it and can post it.

Are these step-by-step instructions available anywhere? Perhaps in PDF/online form?

My 170b's aft floor & side nuts are stripped. My plane has beautiful paint, and I don't want to drill out the rivets in the side of my fuselage.

[c170b53]

Something along the lines of drilling out the old nut plate , then using a magnet to position a new nut plate I think possibly

[GAHorn]

George, there was an article written by C170 member John Gileno #1776 CT describing a method of replacing the nutplates being discussed here that does not require drilling out rivets or cutting holes in the bracket. I have a printed copy of the article that I would be glad to send to someone or to you to post on the forum. I don't know how to do so myself or I would do the posting. I gave a copy to the IA who was doing my mechanical work several years ago and he used the method described to replace the two nutplates in my plane. I don't recall if the article was in the 170 News or was on this forum, but possibly others reading this will recall it and can post it.

Are these step-by-step instructions available anywhere? Perhaps in PDF/online form?

My 170b's aft floor & side nuts are stripped. My plane has beautiful paint, and I don't want to drill out the rivets in the side of my fuselage.

Here is Franks description of the work posted in 2010:

Run a piece of safety wire through the bolt hole (in the nutplate) & up through the space between the top of the bracket and fugelage. This permits retrival of the old nutplate. They twisted a loop in the lower end of the wire so the nut wouln't fall off. Drill out the rivets that hold the nutplate. then pull the old nutplate up through the slot beteen the bracket & the fugelage. (You might have to file the slot some to permit the nutplate to pass through and for the new one to go back inside the bracket.)
Thread the rivet holes in the new cornernut/nutplate with a 6-32 tap. Drill out the rifet holes in brackets with a #28 drill so 6-32 screws will pass.
Insert a piece of safety wire in each enlarged rivet hole in the bracket and push them up throught the slot between the bracket and fuselage. Place the nutplate onto the wires and let slide down into place insied the bracket. Therad a 10-32 bolt through bracket into the nutplate so you can maneuver it into place and secure it with two 6-32 screws. Nutplates are MS 21081-3 or 22NA5-02.
I used the term "nutplate" where the original word "corner nut" was used. Good luck. …

[rschreiber]

We just tackled the aft floor nutplate replacement this week. Thanks to DaveF for the great pictures and the idea for securing the nutplate. It seemed like the best solution considering the space available.