The International Cessna^® 170 Association

I need to get at the rear wing spar to install a shoulder harness. It will require me to remove some of the headliner to gain access to the spar. I see the shark teeth that hold it in place and can guess a couple of ways to get it lose such as inserting a putty knife and pushing in to lossen the cloth. I am looking for suggestions that I may not have thought of. I am all ears. Also, should I start at the front or the rear?

Larry

If your headliner does not have a zipper at the rear spar, either modify your existing headliner by installing one, or replace the headliner with one that has a zipper. I wouldn't consider an annual inspection complete without looking in this area, and it would be much easier just to unzip than to remove the headliner once a year. The zipper should run all the way between the door posts. I've installed shoulder harnesses, removed and replaced antennas, and even replaced the cabin speaker through the zipper, without removing the headliner.

Miles

Miles you would be correct about the zipper direction on a B model but the A model (not sure about the '48 170) the zipper runs down the middle from the spar to the rear of the cabin. Might not allow access for the seat belt doublers to be installed.

I'm thinking Madpilot has an A model otherwise his airplane would already have the nut plate installed in the spar needed to add a shoulder harnesses and he would need (and I would want) to go through the trouble of installing doublers.

It's been at least 7 years since I removed my headliner and had no trouble using just a thin screw driver though a putty knife would have worked better. Just take your time.

BTW one of the advantages of a good headlinerless rat plane is you can inspect the aileron cables every preflight and any pilot sitting in the back can act as a wing leveler by gripping and pulling on the cables.

Larry,

I have a "B" model and have removed the headliner twice, starting at the front. Used a shortened broom stick to roll it (headliner) on as I worked my way back. Found out I could do everything thru the zipper area, or remove headliner only as far as the back window. The good news, if you remove headliner, is you can inspect all the hidden parts.

I also found out the Putty knife worked best, for me, in combination with a thin plastic wedge or plastic puttyknife. However, find a tool that works best for you.

The key is working very slowly.....too not tear the headliner or break off the "metal fangs" that hold the headliner up.

Good luck,

N9149A wrote:Miles you would be correct about the zipper direction on a B model but the A model (not sure about the '48 170) the zipper runs down the middle from the spar to the rear of the cabin. Might not allow access for the seat belt doublers to be installed.

Ha! I didn't recall that A-model zippers ran longitudinally. You learn something every day; now I can relax until tomorrow.

Without assuming any particular year model, I took (possibly mistakenly) Larry's post to mean that he didn't have ANY access to the rear spar without removing the headliner. Even if you already have the attachments, you still need access to the spar to use them...

Miles

I forgot to give all the info. First, I have a 1954 B model. It does not have a zipper installed because it was updated with a after market headliner. It does look like it will be easier to start from the front. I am not sure it there is a doubler on the spar or not. I am not sure about the annual in respect to the control cables but I will figure this out. Thanks for the suggestions.

Larry

Larry, your B-model aircraft will have (already installed from the factory) a #10 nutplate in the rear spar for the purpose of front shoulder-harnesses. You will not have to remove the headliner if you can use your fingers to feel the lower, flat surface of the rear spar hatsection for those holes, and install your harnesses with a NAS229-10 screw (or MS27039-1-10 screw) and large flat washer. Simply punch a hole thru the headliner into the hole with an awl.

Item #7 is the nutplate thru which the screw mounts:

Larry,

I would think you would start from the front and work back because that would be easier than undoing the entire back of the headliner from the baggage area and pulling it all forward. In other words less headliner to remove.

Don't know what shoulder harness doublers your installing. Hopefully it is from an STC'd kit otherwise I would not mess with the spar in any way.

Your spar already has a nut plate installed in it from the factory for shoulder harnesses. It excepts an AN3 bolt to attach the belt the spar. No modifications necessary. I've attached an inertia real system to mine and you could also do a Y belt system without inertia reels. All you will have to do is slit your headliner to allow the belts to come through.

Hmm no zipper. You might want to take this opportunity to completely remove the headliner and have a zipper of some kind installed. Don't know how anyone is inspecting the aileron and flap cables and pulleys.

This thread has a picture showing where to find the factory nut plate on each side of the spar.

http://www.cessna170.org/forums/viewtop ... er+harness

This has been a topic I've been wondering about for a while. I've always heard that only the B models had the factory nut plate installed for the shoulder harness. I've got a 49 A model. The previous owner of 30 years said that the plane had this already in it and he just bolted in a sholder harness. Nothing in the logs prior to his ownership about adding this (and log books never, ever lie right???????) and shoulder harnesses were not installed when he got it. Interesting.

Hey Gahorn

You were right on the money with the nutplate and blueprint. I use a pin and found the hole. The harness kit from Wag Aero fit like a glove. Boy, this save me a lot of time instead of taking down the headliner. It took about 3 hours total, but I am a fussy person. It is hard to believe that a quarter inch bolt is going to hold my fat body from hitting the dash. Thanks again.

madpilot wrote:Hey Gahorn

You were right on the money with the nutplate and blueprint. I use a pin and found the hole. The harness kit from Wag Aero fit like a glove. Boy, this save me a lot of time instead of taking down the headliner. It took about 3 hours total, but I am a fussy person. It is hard to believe that a quarter inch bolt is going to hold my fat body from hitting the dash. Thanks again.

That's actually a 3/16" bolt or screw. But it's in shear, and it will withstand more than your spar carry-through will.

Well LBPilot82 it is difficult in many cases to track down exactly when a small change was made unless it is documented by Cessna and even then I wonder. It is believed that the nut plates started with the B model which makes sense since a new carry through spar assembly was made for these aircraft incorporating other changes to the aileron and flap cable runs. It would be natural the the nut plates were added at this time. But who knows maybe some A models got the plates

I don't exactly recall now but I think I saw an A model spar had the holes but no nut plates. So the holes could be there. It is entirely possible that someone added the nut plates during a repair to the upper cabin skin or do your upper cabin skins have covered holes put there over the spar for the purpose of installing the nut plates. I believe this was one popular way, maybe by an STC, to retro fit shoulder harnesses.

If only our airplanes could talk If sure we would here all sorts of interesting stories how they came to be as they are.