The International Cessna^® 170 Association

Took my first long X-C in really cold weather last week and noticed my left leg was getting fried with the cabin heat full on. I have a 1952 170B with the old style heater that just has the output on the left side. In looking today, noticed it has a 1 1/2 inch tube that comes straight out of the heater (and right on my leg!) - in looking at the parts catalog, it shows a flex hose coming off the tube, but not what it attaches to! It appears like it might go to a defroster duct, but mine doesn't have such. Just where is this hose supposed to go?

In a '52 the 2" scat comes of the left muffler shroud and connects to the heater valve on the fire wall inside the engine compartment. If you include the A model which has the same heat valve on the fire wall there are about 2 or 3 different setups for the scat in the engine compartment.

There should not be any tubing on the inside of the cabin. Just a round metal baffle that looks like it might deflect the hot air throughout the cabin but in reality just fries your left toes or leg if your lucky.

If you have scat inside the cabin it is not original.

This is the valve Bruce is talking about. The left side is mounted inside the plane, the right side is on the engine side of the firewall. These parts were removed from my 1951 170A because I had a C-180 heater system installed to replace the original heater.



The aluminum flex tube was added by persons unknown but it ran across the inside of the firewall and pointed aft into the cockpit just on the right side of the control column. It actually worked fairly well.



Proper original installation on Steve Jacobson's plane.

Richard that flex tube is a nifty idea I hadn't thought of before.

I have no idea where the rectangular flex duct came from and have never seen anything like it since, but it did actually work well enough for Texas winters.

It was gob-welded to the inside half of the heater valve and that center hole was hacked out so the pilot got a little heat no matter what. A "real" craftsman did the job.

It could be aimed left or right enough to customize the flow of warm air to where the whining was the loudest. And if back seat passenger complaints got too loud, I would unfold a sectional chart, roll it up length-wise, stick it over the end of the flex duct, and lay it on top of the tunnel between the seats. It would just reach the back side of the front seats and blow a nice stream of hot air to the back seaters. The radiant heat off the chart could be felt up front. It smelled pretty bad when the ink heated up on the chart but no one complained about that.

It was gob-welded to the inside ..............

Neat another technical term. Gob-Welded, I like it. Is that done with a torch, stick, MIG or TIG?

Only a real craftsman could cut a hole like that. Most people with less talent would use a simple round bit like a drill or hole saw.

I just took note of the duct in your picture of the instrument panel. Funny I've seen that picture a half dozen times before and never noticed it.

Did you notice that fantastic old Cessna Nav-Com with the built-in VOR indicator? I learned to fly using one of those. I hope when Richard replaces it he'll sell it to me!

Bruce-
That was the only term I could think of to properly describe that weld job. It looks like the drip method was used, just keep piling it on until something sticks. It's a thing of beauty! Trying to rationalize why someone might possibly accept work of that quality leads me to believe it might have been done IN-PLACE!

I had no idea that picture would get so much mileage when I took it.


George-
That NavCom 300 was the only radio I had from 1973 to 1979. It's been repaired with everything from Radio Shack to RCA TV parts and it was STILL working (illegally) when it was removed in 2006. The VOR was so sensitive it would indicate anywhere within about 15-20 miles of the station. How much is it worth to you? Let's see, with the tray and harness.......maybe a case of Lone Star? OOPS, we better take this conversation to the The TradeMart before we get busted!

I've got a KX-170 in the same condition and dinner at my place I'll trade you for it!

George- Dinner sounds good but you can keep your old radio, I have boxes of them. Need a good Mk-12, or a Bendix ADF? We might work this deal into a regular Wednesday night special at your place.

I'd like an old self-contained ADF (w/indicator in the radio.)

I do great fajitas, smoked chicken, ribs, rib-eyes, and hand-made ha\mburgers.

In the picture above it appears that the cabin heat comes from only the left exhaust shroud and the right exhaust is scat to the carb heat. I have a 1950 C170A and on mine the heater scat hoses come from both exhaust then join at the carb heat box by a Y shaped connection then run to the firewall. Still I get little heat.
NOw why would mine be different?

I just happen to have a photo of my 170A’s heater hose layout. I seem to stay warm although I also rode my motorcycle to work this morning – it was one degree below freezing



Mark

Curtis yours is different because it is one of those exceptions you will find in some A model heater plumbing that I was talking about.

It is fine the way it is as that is how some came. I've seen this on about one out of 10 A models I look at. And because I'm interested it IS one of those things I always check when I see a 170.

Unfortunitly you don't get any more heat. I know because I plumbed mine that way to see if it made any difference.

How many have seen the optional heat duct that runs up the center flap handle hump distributing heat better to the front seats and even the rear seat?. This optional plumbing method you have Curtis was used with that optional system. A good friend of mine has it in his. But I have seen it without the duct done the center flap handle hump.

WHOAAAA!!!! It looks like you have a post-53 B-model right exaust heater muffler/shroud, Mark! (No wonder you have sufficient heat!) If you have that set up, you should be able to get MUCH more heat than an original A-model.

It looks like your right side has been necked-down from the post-53 3-inch heater hoses to the earlier hoses (which then go to the "Y" at the carb.) This reduces the heat available from that post-53 heater muff/shroud.

Of course, the other restriction is the small heat distribution valve at the firewall. If you could get rid of that hose size-reduction and assure that you have a 3" inlet as well, and perhaps obtain the later firewall heater valve (used on late B-models and all the 60's 172's) and get that heat distributed inside the cabin.... you should have plenty of heat. (I keep my cabin heat turned down, only running it at partial-heat even in the coldest weather, in my 53 B-model.)