'48 Exhaust Shrouds and Ducting

[GAHorn]

Those are certainly good words, John. And I think we're saying the same thing.... do it like Cessna did it ...because that's how it was done and approved on the Type Certificate. (Hanlon-Wilson muffs and carb heat are approved per the TCDS, in accordance with Cessna Dwgs, which is illustrated in the IPC.)

Here it is again, showing the left muff connecting to the carb heat, via a 180-degree turn/elbow (item 34.)

exhaust brace.JPG

[Bruce Fenstermacher]

Well after further investigation it appears I didn't actually see a Cessna picture of 2 inch duct from the right side to the carb heat and the left side to the left side 2 inch cabin heat manifold (I'm still looking though )

But to review the pictures George posted from the IPC here is what we have. With the pancake style mufflers and the 2 inch scat both the left and the right side go to a Y at the carb heat. Then a 2 inch scat goes to the cabin heat manifold on the left side of the firewall.

Although I couldn't find it anywhere on the TCDS rev 54, we (think we) know the Hanlon Wilson mufflers are approved for the earlier aircraft. The type certificate says the Hanlon Wilson system should be installed per Cessna drawing 0550157. Cessna drawing 0550157 is not the IPC though the IPC might be the same.

Any one seen Cessna drawing 0550157?

George where again does it state that the Hanlon Wilson's are approved for the 170 and 170A? Perhaps that wording could give us a clue.

The picture in the IPC of the B model does in fact show just the left side going to the carb heat. And the right side with the bigger scat going to the cabin heat manifold which for this installation was on the right. It doesn't show it crossing all the way to the left side. So doing so would not be the way Cessna did it. They didn't use 2 inch scat and they didn't cross from the right muffler to the left.

We know that the left muffler and shroud system for serial numbers 20267 thru 25372 is exactly the same as the right side by part number. If on the later B model the left side alone can produce enough heat for the carb heat then so can just the right. They are the same.

My mufflers, shrouds and 2 inch scat, which are the same each side, have been plumbed with the right side only to the carb heat and the left side only to the cabin heat manifold for 10 years except for about 2 months when I experimented with the addition of the Y connector. While I'd like to say my airplane makes this installation legal, it doesn't But I can tell you I have plenty of carb heat.

So at this point being that we are talking a '48 which should have identical Hanlon Wilson systems left and right with 2 inch scat, the only difference from stock being the mufflers and shrouds. I think without further evidence the only way we can definitely say this airplane should be plumbed is following the IPC for the '48 and using a Y pipe.

[GAHorn]

The approval basis for all 170s to convert to the Hanlon-Wilson exhaust system is the Type Certificate Data Sheet which specifes that the system is to be installed according to Cessna drawing 0550157.

Cessna parts numbers are derived from Cessna drawing numbers. In other words, a drawing number of 0550157 would be descriptive of the installation of part number 0550157. Since the PN 0550157 is specifically "Stack Assembly - Engine Exhaust, L.H." per the IPC, Pg 89... that would indicate the illustration in the IPC reflects that drawing.

(And that does indeed depict the left hand muffler as providing heat for the carburetor. It does not depict it providing heat to the cabin. That leaves only one other device to heat the cabin, that I can think of, and that is PN 0550157-1....which does not have an approved drawing specified in the TCDS. That may be due to cabin heat being optional, not required, equipment.)

[Bruce Fenstermacher]

The approval basis for all 170s to convert to the Hanlon-Wilson exhaust system is the Type Certificate Data Sheet which specifes that the system is to be installed according to Cessna drawing 0550157.

OK asked another way. Where on the TDCS does it say this? I'm sure at one time I've seen it but I could not find it on the version 54 I look at. I've looked several times and can not find it.

[GAHorn]

The approval basis for all 170s to convert to the Hanlon-Wilson exhaust system is the Type Certificate Data Sheet which specifes that the system is to be installed according to Cessna drawing 0550157.

OK asked another way. Where on the TDCS does it say this? I'm sure at one time I've seen it but I could not find it on the version 54 I look at. I've looked several times and can not find it.

Did you see/read Item 110 under the "Engines and Accessories" heading?

110. Hanlon-Wilson exhaust manifolds and carburetor
air heater (Cessna dwg. 0550157)

[Bruce Fenstermacher]

Yes I saw that and it is only for the B model. Looking at the list of required equipment for each model the respective number for the stock exhaust for the 170 and 170A model is listed as item 103. Were does it say specifically that item 110 can be installed on the 170 and 170A models or serial numbers earlier than the B model in lieu of item 103?

This is why I asked if anyone had seen Cessna drawing 055157. Perhaps there are more clues there. The IPC may show the same drawing but it is not Cessna drawing 055157 because it is not labeled as such. And in this case the IPC is serial number specific which doesn't cover 170 and 170A aircraft. So how would one justify using a unlabeled picture in a parts manual for a newer model plane to install the newer stuff in the older model? Indeed how would you use an unlabeled picture in a IPC in stead of a specified drawing on a B model?

What I'm saying is we have to know 055157 is exactly the same as the B model parts manual picture in order to use it as a reference forn installations on any model 170.

I'm sure I've seen approval for the use of item 110 in leu of item 103 in older models somewhere, but then I also swear I saw a picture of the right muffler feeding the carb heat manifold.

[GAHorn]

Item 110 is not listed as "required equipment" for the 170 or 170A. It is listed under "pertinent to all models" equipment. Those are seperate sections of the type certificate and, I believe, form the basis for approval of installation in all models. This would be the same situation if any other equipment such as increased-capacity generators were installed.

The IPC is not "an unlabeled picture". It is described by the listing on the following page which identifies it as the 0550157 assembly. IMO

[Bruce Fenstermacher]

Yes I see the paragraph now under Equipment at the head of the list of equipment. I knew it was there but overlooked this because I remembered it as being more specific to item 110.

What I meant by unlabeled is that the depiction is not labeled drawing #055157. Yes we are splitting hairs here but I think an important hair the FAA will split if they want to.

[GAHorn]

...Cessna parts numbers are derived from Cessna drawing numbers. In other words, a drawing number of 0550157 would be descriptive of the installation of part number 0550157. Since the PN 0550157 is specifically "Stack Assembly - Engine Exhaust, L.H." per the IPC, Pg 89... that would indicate the illustration in the IPC reflects that drawing....

I don't think that even the SAT FSDO would give any trouble over using this IPC illustration to install a PN 0550157 since that is the PN described in the text and carries the same number as the dwg to which refers. Only my opinion, of course.

[mrpibb]

This what I have, we made a reducer for the right hand side, hope this helps
Vic



and

[Bruce Fenstermacher]

Hey Vic looks like you have the accessory heat ducting running down the center cabin tunnel. I've only seen a few of these.

It should be noted that the 3 inch opening you have in the front baffle is not standard for a '48. Also for those that might be looking for the Y pipe I believe they were used on early 150/152s besides our 170s. I once bought one for $5 out of a junk box at Sun N Fun.

Where did you get the 3 to 2 inch adapter?

[mrpibb]

yep, mine is a early one, its okay on a sunny day during the winter as long as you bring rags to wipe the frost off the inside of the windscreen. Now as far as standard......

[GAHorn]

Well...the plot thickens...
MrPibb.... it appears your re-use of the"Y" fitting is illegal according to Cessna.....their SK 70A51-1 (Thank you Glenn Hetchler...)... under the "CAUTION" section it states:
"The carburetor heater union must be removed. The new exhausts stacks are not approved for use with this union."

(See the MX Library for a complete copy of SK70A51-1 which contains installation instructions and drawings for conversions to Hanlon Wilson Mufflers.)

Note: The SK70A51-1 conflicts with dwg 0550159 in that it directs the left muff to cabin heat and the right muff to carb heat, so depending upon the installation instruction with which you comply with this installation, will apparently determine which way you hook it up. And I thought this was such a simple thing.....even Cessna has two different ways to comply...

[Bruce Fenstermacher]

I don't know which airplane Bruce is referring when he says that is the way Cessna did it... because all the airplanes with the H-W system we're discussing uses the LEFT muff for carb heat and the RIGHT muff for cabin heat ....and that's the way I recommend you to also connect them. .........

Wellllll how about that. SK70A51-1 is were I must have seen "Cessna do it". Looks like I was right for the second time this year.


The caution about the Y pipe would make sense in Cessna's mind because they have directed you to put the left duct directly to the cabin heat manifold leaving two of the three ports on the Y pipe open. Having the open ports on the Y would allow cold fresh air to mix with any heated and and likely effect carb heat. Of course most people would realize the open ports on the Y wouldn't work well and either connect both ducts like the original or remove the Y.

I think the caution statement is an early "cover your butt" statement of many more to come by Cessna and connecting the Y from both sides as original works just fine. But this in a moot point as the statement contained in SK70A51-1 takes that option away.

[GAHorn]

I don't know which airplane Bruce is referring when he says that is the way Cessna did it... because all the airplanes with the H-W system we're discussing uses the LEFT muff for carb heat and the RIGHT muff for cabin heat ....and that's the way I recommend you to also connect them. .........

...

Wellllll how about that. SK70A51-1 is were I must have seen "Cessna do it". Looks like I was right for the second time this year.

His RH muffler has no lips at the ends, and the air comes in at the front and exits at the rear - if it had the lips on the muffler ends then the air wouldn't pass over the shroud, so really poor airflow through the heat muff and not much heat. With no lips for the shroud to ride on, it's optimized for more airflow over the muffler to serve as a cabin heater, no matter if you have 2" or bigger hoses.

...When Cessna went to the 3 inch scat on the right side ....

You're right a lot more than twice in a year! This just goes to show there's always more than one way to skin a cat....we just need to make sure that whichever way we try to do it is an approved method. We were talking about doing it in accordance with the TCDS or dwg 0550159, not a service kit.

"All the airplanes we're discussing...." ... refered by me were those with the 3" inlets, which are '53 and later B-models...and....those installed by Cessna or others under dwg 0550159, per the TCDS.