Seat Rail Replacement

[cessna170bdriver]

Looks like it's time for new seat rails. I've actually been surprised at each of the last several annuals that they had passed. They look bad enough that I'm not even going to check them this year. The replacement looks fairly straightforward. All the rivets look accessible without having to make/procure any Rube Goldberg bucking bars. Any "gotchas" from the pros? (My AI and I will be sharing the gun and bucking duties. )

[Bruce Fenstermacher]

I'm not an expert but I have replaced one seat rail in a 170 which makes me an Xspert compared to you Miles.

It's been 6 or more years. I only changed the pilots side with the holes. I did not have any unusually bucking bars to do this. In fact I only recall a few rivets that took a little extra effort to be bucked.

Of course I wanted to use the same old holes for the new rail as the old one used. On order to do that I placed a sacrificial piece of aluminum for a template on the floor over the holes. Using a hole locator I drilled holes in the template. Removed the template and placed correctly (be careful here, don't get it upside down) and used it to carefully predrill the new seat rail. Worked perfectly.

The question you have to ask is this. If I did this six years ago and assuming that seat rail is unique to that aircraft. An aircraft that I no longer own and it might never fly again. Why would I still have the scrap template I made? And for a bonus clue. Why would I be able to put my hands on this template so quickly and easily?

The answer of course is this. There is no way in heck I'll ever need this again or be able to use it for anything other than a back scratch. That is why I've kept it and know exactly were it is. In my pile of ever expanding back scratches.

[170C]

How about replacing the rivets with the proper bolts/nuts? Pretty sure that was what my IA at the time did in mine. Would make future removal, if needed, simple.

[mike roe]

If I am not mistaken when using screws and nuts the holes in the rail have to be spotfaced and alondined. Not many have the spotface bit. Something else you would need.

[ptporebski]

I saw the new AD and measured my seat rails. Looks as though 4 new rails will be in my future. I ought to buy them now and beat the rush!!

More joys of ownership!!

[Bruce Fenstermacher]

Looks as though 4 new rails will be in my future.

So this begs the question. Why replace the two seat rails that are not drilled as long as they are not cracked or broken in any manner? Most of the wear is in the holes for the seat stop and the seat stop itself. Then rollers, specially those with flat spots from not rolling as they should.

When I bought and replaced mine I only did the worn one with the seat stops drilled. I was careful to buy a new rail that matched the old original. "New and improved" rails are available and may not match the old in height. If you could buy rails that didn't match the old then I could see the necessity for replacing them in pairs. Otherwise I don't.

[cessna170bdriver]

My AI and I took a closer look yesterday. The plan is to carefully drill out the old rails, then make templates by match drilling through the rails, then match drill the new rails to the templates. Looks like the forward two rivets in the outboard rails may require partial removal of a couple of bolts in the landing gear bulkhead.

The new AD (to be effective June 17) is MUCH more stringent than the last one, requiring dimensional checks on just about every part in the seat-to-rail interface. I'm just going to replace all four 50+ year-old rails and all 8 rollers, and be done with it for another 50+ years, hopefully. I got the rollers as a door prize (or did I overpay for them at the auction?) at a convention many moons ago.

How about replacing the rivets with the proper bolts/nuts? Pretty sure that was what my IA at the time did in mine. Would make future removal, if needed, simple.

Frank, I'm building a Harmon Rocket, so I'm used to drilling and re-riveting (though the universal rivets do challenge me more than flush ones). Replacing rivets with screws is for wussies, right Ed B?

I saw the new AD and measured my seat rails. Looks as though 4 new rails will be in my future. I ought to buy them now and beat the rush!! ...

My thoughts exactly. McFarlane currently lists the rails as "stock", but that could change as soon as airplanes start getting inspected after the new AD hits the street.

[GAHorn]

I see this as just ONE MORE reason I was right and my critics weren't when they said I was crazy to pay $43K for a 170, that NO 170 , not even a fully-restored one, was worth that much money, it didn't matter that every single thing on it was new.

But every time I hear someone complain about the cost of corrosion, or windows/windshields, exhaust systems, air boxes, control cables, wiring, interiors or paint...the list goes on and on and on.... I realize how CHEAPLY I acquired my airplane. I've flown it for 12 years now and have never spent more than $500 in any year for inspections/mx ...and that includes the year I replaced spark plugs.

[bagarre]

I was going to feel real sick about how much I paid for mine until I saw that yours was $43k twelve years ago

But yes, It's far cheaper in the long run to buy it done.

A quick look at my rails tells me I get to learn how to rivet this year too!

[DaveF]

I just replaced my pilot side rails. I bought the new rails from MacFarlane, and in a burst of extravagance, bought the blank template strips, too. The replacement job was easy.

My rails were attached with -4 universal head rivets in all locations except the two at RH aft, where a control pulley under the floor prevents access by bucking bar, and LH forward, where a large bolt (strut attach IIRC) is in the way. I used Cherrymax rivets in those locations. The two RH fwd holes had been drilled oversize in a previous replacement so I used -5 rivets there.

I thought I'd need a transfer punch to locate the holes in the templates, but that wasn't necessary. The old rails made very nice drill guides and the holes transferred to the new rails almost perfectly. I used the drilled template strips under the floor as doublers.

[Bruce Fenstermacher]

So no one has commented. Why replace the right rail on each seat that is not drilled full of holes that are worn and where the cracks appear.?

[GAHorn]

It's a personal choice, I suppose. If the rail isn't worn thin, cracked, etc etc,... i.e., if it's airworthy... then it's a matter of choice. Keep in mind that some chair-leg-feet and roller are worn and may not be depended upon to retain the seat in turbulence or an accident/ground-loop. It'd be a shame if someone got hurt because of some ill-conceived scheme to save a few buck.

While on the subject of seat rails... HOw many know the number ONE cause for seat rail cracks?
(Answer: Heavy persons who sit and stress/flex the floor leading to rail cracks... and those who vigorously/abusively
adjust, slip, slide, slam the seats about when adjusting them.
These things are like DOORS. They are old, rare, and expensive. Teach your pax to NOT lean on the doors when they embark/deplane, and NOT to be rough with the seat adjustments. DON"T push back on the seat-back when sliding the seat aft. DON"T unlatch the seat and release the handle to allow the locking-pin to slide and fall into the hole ( rounds-off the locking holes and damages the rail.) DON"T get rough with these seats. ALL components of the aircraft cabin and furnishings are not like a Greyhound bus...they are like fine, French furniture ... and no one makes this sutff anymore! Let's keep 'em in flying condition by taking care of them.

[cessna170bdriver]

Got all four seat rails out this weekend. Getting some of the bucktails out was a real pain in the arse. The one on the aft outboard corner of the pilot-side outboard rail refused to budge even after drilling out to 1/8" (#4 rivet). I could get a hold on it with a small pair of end cutters, but it wouldn't budge. WTF?

Since we had the mirrors and flashlight out for the annual inspection anyway, we abandonded the braille method and took a look under the floor and found that when the existing seat rails had been installed, the flange on the crossmember under the floor at the rear door post had not been pulled up tight against the floor panel, and there were TWO bucktails on the rivet, one where it should have been and another BETWEEN the crossmember flange and floor panel.

On the advice of my AI, I used his close-quarters right-angle drill with about a 1/4" bit to remove the outer bucktail, then got a hook behind the one in between the parts. Takes about a minute to type what I did, and more than an hour to pull it off. After several tries at the proper configuraton of tools and hands, I made it work by threading the air hose through a forward access hole in the floor, through the bulkhead/crossmember at mid-door to the drill in the bay with the offending bucktail. My left hand through the access cover behind the flap handle to the forward end of the drill (and a moderate amount of purple language ) to place and hold the bit, and my right hand through a floor access cover just forward of the rear door post to balance the drill and pull the trigger. After that it was a simple matter to hook and remove the offending @#$%^&*.

I didn't have the camera with me at the time (and was't really in the mood to try to take a picture in the mirror , but I will try to get a closeup of the rivet shank with a bucktail in the middle.

Now on to the next step. My plan was to make templates for drilling the new rails, a la Bruce, but when I put the two rails for one seat back-to-back, I noticed that the hole patterns match perfectly (they are exact mirror images when right-side-up). Unless someone tells me why I shouldn't, I'm going to use each seat's old outboard rail as a template to drill the new inboard rail, and vice-versa.

Oh, yeah. I found another reason to replace the rail without the seat stop holes: there were several small spots of corrosion between the seat rails and the floor panel. Not enough to be structural concern, but enough to warrant about an hour with scotchbrite and primer to clean them up. Theoretically, one could remove the rails, check for/deal with any corrosion, and reinstall the rails, but for me personally, I wouldn't remove a rail a second time for the price of a new one. Pictures are still safely stored away in the camera. I'll post when I have time...

[lowNslow]

Miles, now that you got this all down I'll bring my bird down Tehachapi so you can install my new rails.

[cessna170bdriver]

Miles, now that you got this all down I'll bring my bird down Tehachapi so you can install my new rails.

Karl,
My AI estimates 9-10 hours labor if he were to do it. You want his number? I'd charge you an equivalent amount in beer, but then I wouldn't be able to help.