The International Cessna^® 170 Association

It's probably not a good idea that my wife and I moved back home. With my family's airplane hangared three minutes from my parents house and the same from the house my wife and I are trying to buy, I tend to find myself oogling over it probably more now than I ever did before.

That said, I'm noticing more warts on the airplane than I recall, so I've got my gears turning. I've got two questions today that don't necessarily pertain to 170s exclusively, although the desire is to apply the answers to them.

First of all, it appears as though the quick drains are safety wired through a small hole in the skin adjacent to the relief for the drain. On both sides on 56D, the original hole has torn through to the main relief hole, and a new hole has been drilled. There is a 1997 182S on the field, and I noticed the other day that Cessna has figured out how to improve on what they did in the 1950s, probably given that there are 13 quick drains on the airplane. There appears to be an internal doubler that seals the drain a little better, but more importantly, there is a small bracket to which the drain is safetied. If one wanted to do this to a C170, what would be the ramifications? Ordinarily I would see this as a minor alteration, but because it involves the fuel system, I would see easily how it could be a major alteration. Thoughts?

Secondly, there are the remains of a couple antennas on the top fuselage skin, P/N 0513000-19. Is this a piece than can easily be replicated with sheet metal, or is this a formed piece that will require purchasing the skin from Cessna to achieve a good fit? I'm curious as to what they could have been used for. One was installed when my grandfather bought the airplane, but the one in the front was long gone.

In my opinion riveting a small tab to the skin for the sole purpose of safety wiring the valve is minor. I'd probably just fashion a flat doubler "fix" over the rip in the skin and just drill a new hole in it for the safety. Problem is you can't get to the back side of this area to buck the rivet(s) without removing the tank so the "fix" is not a quick and easy one.

If you look in the IPC you will see all sorts of antenna installation. The knob in your picture is for a wire that stretched up over the windshield, through a bracket that is likely on this airplane and then back to the tail where you will likely find another bracket. Hard to say what type of antenna was mounted in that front hole. Maybe just a stainless rod.

This area was a popular place to mount the antenna of the time. It was as close the radio as you could get and in the case of the wire type there was enough length for it back to the tail.

My own 170 has the remnants of about 13 antenna installations. I have removed a few of them over time but to be honest almost didn't. I feel the antenna installs show the history and are part of the beauty of these old birds. I've often considered reinstalling all the antenna even though they would not be functional.

Oh as for replacing the sheet, anything is possible. $$$$$$$$$

Replacing that sheet is a major operation. It goes under the windshield and is also the glare shield. So the windshield would have to come out and rivets shot back in some hard to get access to areas with instruments installed. The engine might also have to be removed or at the least stay on a engine hoist or something to take the weight off the airframe. Are the holes starting to look a little better now.
Mike Roe

mike roe wrote:Replacing that sheet is a major operation. It goes under the windshield and is also the glare shield. So the windshield would have to come out and rivets shot back in some hard to get access to areas with instruments installed. The engine might also have to be removed or at the least stay on a engine hoist or something to take the weight off the airframe. Are the holes starting to look a little better now.
Mike Roe

At the risk of sounding dense...no. I was surprised to see what this part actually was in the IPC, but those holes are still ugly and a patch is even uglier. Surely you can sympathize given the fact that you tore apart what was, as best as I could tell, an extraordinary nice airplane to make it even nicer. I have somehow ended up with a bunch of pictures of your Stinson on my computer as well, and it's evident to me that you are quite the perfectionist.

Adding tabs to safety the quick drains-minor alteration. Also a great opportunity to remove the tanks, clean and inspect tanks, fuel bay, inspect spar cap for corrosion, and replace deteriorated hoses. Also replace damaged nutplates and install new tank top screws. Get crazy and replace the wood blocks and neoprene chaff strips while your in there. If you dont want to go this far, I have seen an alternate method of safety wiring the drains. This is to drill a hole in the skin next to the drain relief hole, install a riv-nut, and then install a filister head screw into the nut riv-nut. Safety the drain valve to the screw. This method is not preferred, but very functional and simple.

That skin is easy to local fab, and easy to replace AFTER you have good access. As Mike said, you will need to either remove or support the engine. I recommend about 2 hours of work to remove clamps, tyraps, and disconnect fuel hose, throttle cable, mixture cable, and carb heat cable at carb. Then remove the 4 bolts at the mount/firewall an ease the engine forward a couple inches. Block your cherry picker and leave it hanging until your ready to reinstall. You have a fair amount of work to remove some instruments and windshield, but the skin replacement itself is not a big deal.

Thanks for the compliment (I think) sometimes trying to make things perfect can get expensive and annoying. I think it's a sickness but it's to late in life to get treatment.
Mike Roe

mike roe wrote:Thanks for the compliment (I think) sometimes trying to make things perfect can get expensive and annoying. I think it's a sickness but it's to late in life to get treatment.
Mike Roe

That was indeed a very sincere compliment. Your workmanship is immaculate, and you take great pride in your toys.

Thanks Ryan. Another option if you were to paint that area are some flush patches. A good sheet metal person and yourself would be the only two who would know.
Mike

The 182 has different fuel tanks (bladder type) which need to be secured well in numerous places. Those drains help achieve this and is why they are better secured to the lower skin. (The tank uppers are held by clips top prevent empty tanks from collapsing.)

Quick drains have no mechanical stress on them and the safety-wire does not need to be tightly attached. (Heavy-handed wire safetying is what usually tears out the holes, although years of vibration will also contribute.) A tab such as illustrated on the 182 is a minor alteration. (A tab that is attached with structural adhesive is as well, and the safety wire will actually help hold it in place when you drill a new hole.)

I also had the hole in one of my safety wired drains torn out. I eventually drilled a new hole for the safety wire (may have been when I had the tanks out?) Like a lot of things on aircraft, I guess having safety wire on them is a good idea, but I have to wonder if there is any real danger of those drain valves backing out. If they did so I suspect one would notice fuel dripping a long time before the situation would be critical enough to drain much volume of fuel. Just an observation.

I guess I never noticed that the fuel tank drains on those modern A and B models were safety-wired, and my '48 Ragwing's are not.

Of course, the '48 fuel drains are 1/8 inch pipe thread rather than the 7/16-20 straight thread that the A's and B's are.

Am I negligent in not having mine safetied somehow?
Or are the 1/8 inch pipe thread drains less susceptible to backing out?

Pipe threads don't tend to walk out as they are tapered. So, they stay tight.
If a straight thread walks, it becomes loose and will continue to walk.

None of the other fittings in our fuel system are safetied.