Carb Temp variations in Pponk'd C180s

[mvivion]

Maybe I am wrong, but I always either had full carb heat or no carb heat never partial, just cause temp gauge says its cold enough for ice means very little in my opinion

That is the most common advice, probably because carb air temperature gauges aren't that common in most airplanes.

They are fairly common in Cessna 180/182s, at least the older ones. That is because those airplanes do tend to make ice a bit more than other airplanes. If it is equipped with a carb temperature gauge, there's no problem running partial carb heat. Only down side is you're feeding unfiltered air into the engine, but at altitude that shouldn't be an issue.

Fly a Beaver sometime.....the POH calls for carb heat any time they're in the right conditions. POH says run sufficient carb heat to keep carb inlet temp at or above + 4 C (or was that +7C? Been a while.). Pull on full carb heat and it'll sound like the engine is dying...great way to scare passengers.

MTV

 

[Dave Calkins]

4 deg C for the Beav.

One operator I flew for didnt train for maintaining it as I recall about carb air temp or carb heat settings in the Beav other than it being in the TO and landing checklist for "cold". As I recall.


A different operator I flew for last season had a very specific regimen for setting carb air temp and maintaining 4 C per DeHavilland specs with partial carb heat.

I also run partial carb heat on my 180 every flight it seems. That had been normal 180 ops for me before flying Beavers.

 

[Randyk]

The big reason for maintaining the Beaver carb temp above +4C is for proper atomization of fuel according to the POH I read some time ago.

 

[Randyk]

I had a P-Ponk 180. Had a big variation with the EGT's front to back. Turns out there are three sizes of crossover tubes, I had the "medium". When I changed to the "large", they got closer but I still had to run partial carb heat to get them within a reasonable range. (And no, I did not have an induction leak.) I have heard of others going to the smaller tube with like results. YMMV

 

[stewartb]

The best thing I ever did to level EGTs and CHTs was to increase the fuel flow. I can still lean it to the flow rate I used to have but temps are definitely better now. It may not make perfect sense but it's true. My engine has always been a little leaner than I'd like. Not any more. Take off fuel flow in a Pponk engine should in the into the 20-something gph. Any less and it won't have enough fuel flow for cold weather. That's when I used to see my greatest temp spreads.

 

[mvivion]

The big reason for maintaining the Beaver carb temp above +4C is for proper atomization of fuel according to the POH I read some time ago.

Now that you mention it, I recall that advice as well. When I was getting checked out Jerry Lawhorne told me "when that check pilot gets done checking you out in your airplane, you come talk to me, and I'll tell you how you're gonna run MY engine." Jerry was our Chief of Maintenance and he knew more about 985s than just about anyone I ever met.

MTV

 

[CenterHillAg]

Is that carb heat reccomendation specific to the Beaver, or do the 985's tend to make ice in general?

 

[sj]

The best thing I ever did to level EGTs and CHTs was to increase the fuel flow. I can still lean it to the flow rate I used to have but temps are definitely better now. It may not make perfect sense but it's true. My engine has always been a little leaner than I'd like. Not any more. Take off fuel flow in a Pponk engine should in the into the 20-something gph. Any less and it won't have enough fuel flow for cold weather. That's when I used to see my greatest temp spreads.

Further, if you have less than 20+ fuel flow on takeoff it might mean the carb was not jetted right - and you will burn up exhaust valves - which I know from experience.

sj

 

[Steve Pierce]

I had a P-Ponk 180. Had a big variation with the EGT's front to back. Turns out there are three sizes of crossover tubes, I had the "medium". When I changed to the "large", they got closer but I still had to run partial carb heat to get them within a reasonable range. (And no, I did not have an induction leak.) I have heard of others going to the smaller tube with like results. YMMV

I was thinking Steve Knopp told me to use the smallest balance tube.

I ran a 53 model 180 up on a cool day and saw frost form on the induction Y. Cool day in Texas is about 60 degrees.

 

[bubb2]

P.Ponk 180 Ice

I have an EI carb temp gauge in my 55 c180 and pretty much ALWAYS winter or summer, have to have at least a little carb heat on to keep it out of the "ice zone". It has proven at night over Pennsylvania that it can make ice like a Manitowoc ice machine - in fact, enough that it won't clear all the way even with full car heat.

The other day I flew in a gorgeous 59 c180 with a PPonk and asked the owner about his carb temps. 135 degrees and he never uses carb heat, never had ice, etc. It was about 30 degrees out that day.

I have the "small" crossover tube on my engine which is what is prescribed to help with this problem.

The cowling intakes are different on these two planes.

Any ideas?

sj

I own and fly a 1954 Cessna 180 that currently has an P.Ponk engine. I have owned the airplane since 1982. I have had 3 different engines in this plane, the original o-470-J, an o-470-R and now the o-470-50. The O-470-50 is an original io-520-D with the original high compression pistons (by field approval). Back in the day I remember thinking how "ice free" the old J beater was. I think the only time I ever had to use carb heat in cruise was flying low level over Lake Iliamna during a rain storm. The aircraft was equipped with the factory original carb heat gauge and probe. Those early carb temp setup's were not very accurate as the probe was in the air box, not the carburetor throat. I think it was only telling you the temperature of the air BEFORE it enters the carburetor. When I installed the o-470-R I discovered why the J beater almost never produced ice, the rubber seal in the air box valve was all but gone. Having a temperature probe forward of the carburetor and an almost non-existent seal in my air box, I had been unknowingly running around with partial carburetor heat for years. I then replaced the rubber seal and installed a cheap Westach gauge and probe. At least the probe was now located in the carburetor. I did experience the cross over tube icing condition with the O-470-R once while crossing the Alaska Range during the winter. For whatever the reason the rough running engine could not be smoothed out with carb heat or mixture adjustment. What was funny is that it occurred during a climb at about 7000 feet (an altitude way over my usual 1000 feet). If I stopped the climb and descended to 6800 the roughness stopped. If I started the climb again the engine would run rough again right at 7000. I just stayed at 6800. Talking with Alaskan Aircraft Engines they told we to switch to the bigger cross over tube and insulate it. I have done that and never experienced that problem again. I now have the P.Ponk engine with an EDM-900. If you want to get overloaded with data get an EDM-900, one could spend a life time trying to decipher what is causing a multitude of engine parameters you were totally unaware of before the EDM's install. I know now my carb box valve seals well so there is little to no heated air leaking into the carb with the carb heat in the cold position. I would say the o-470-50 is an ice maker. Partial carb heat is required to operate on most Alaskan summer days. If not used you will constantly see a slow decrees in manifold pressure. The accuracy of the EDM allows partial cab heat to maintain a temp just above freezing. Set it and forget it. But I'm thinking just get rid of the carburetor and install RSA fuel Injection. Working to get that done now.

 

[sj]

bubb2, I looked at the RSA website, it does not appear to be available for 470/520 engines only 360's and 540's. I may be reading it wrong or looking in the wrong place.

What do you think an install like that will cost? (FI upgrade that is).

Thanks for post and for the info!

sj

 

[skywagon8a]

bubb2, I looked at the RSA website, it does not appear to be available for 470/520 engines only 360's and 540's. I may be reading it wrong or looking in the wrong place.

What do you think an install like that will cost? (FI upgrade that is).

Thanks for post and for the info!

sj

sj,
The RSA system is generally for the Lycoming engines. The big Continentals use a different system from Continental. You might research the STC list. I believe that I've seen an STC to install an RSA system on a big Continental. Also you will need to install a fuel pump along with an auxiliary fuel pump. The Continental system requires a return line back to the fuel tank where the RSA system does not.

 

[skywagon8a]

The other day I flew in a gorgeous 59 c180 with a PPonk and asked the owner about his carb temps. 135 degrees and he never uses carb heat, never had ice, etc. It was about 30 degrees out that day.
Any ideas?

sj

If your friend's carb temp was 135* he's getting heat from somewhere.

sj, stewart is correct that other 180 has leakage somewhere in the system. When the carb heat control is "cold" the temperature should never be above ambient. That other 180 is leaving some horsepower behind in the barn.

 

[sj]

Thanks, the bigger deal though, is that his no carb heat temp is higher than my full carb heat temp ever is...

sj

 

[stewartb]

So fix it. What's taking you so long?

 

[sj]

So far, no clear idea of what the problem is. The crossover issue seems to be more related to the crossover freezing than cold carb temp. Can't afford fuel injection, and I don't have the carb box problem as I am ambient or less when idling.

sj

 

[stewartb]

Did you insulate the balance tube? Did it impact EGTs at the front cylinders?

That has nothing to do with carb ice or lack of a robust carb heat source to manage carb ice. What is this thread about?

 

[sj]

Stewart, I did not, but it does the same thing at ambient temps of 90+ degrees so that exercise seemed moot to solving the problem, unless I am misunderstanding the crossover insulation which I thought was to combat cold ambient air.

sj

 

[bubb2]

RSA Injection in O-470-50

bubb2, I looked at the RSA website, it does not appear to be available for 470/520 engines only 360's and 540's. I may be reading it wrong or looking in the wrong place.

What do you think an install like that will cost? (FI upgrade that is).

Thanks for post and for the info!

sj

If you are truly interested in the RSA fuel injection let me know. Precision Airmotive has the printed data from an old Bendix STC to install RSA fuel injection in a Continental O-470 engine and in a Cessna 180 or 182. You have to get a field approval to use the data for install in the O-470-50 and most of the components called out in the STC have been superseded. I had most of this data approved on a 337 field approval about 12 years ago. While acquiring the components I noted I needed approval for substitute check valves, fuel air nozzles and the flow divider. I also plan on a couple deviations to the original STC such as retaining the manual priming system and my fuel Flow/pressure indicators (EDM-900) varies from what is called out in the STC. This will require a modification to the Flight Manual Supplement provided in the STC. This Field Approval request is currently being worked by the FAA. I think it's cost me about $5000 for the components, most in overhauled condition. As I am an A&P with IA my labor costs will be $0.

 

[180Marty]

couple deviations to the original STC such as retaining the manual priming system

Can you explain how that works---sounds interesting.

 

[bubb2]

Can you explain how that works---sounds interesting.

The original STC's (SE1CE and STC 108CE) instructions call for the complete removal of the priming system. This is noted on the Flight Manual Supplement (part of the STC) in the Normal Starting section. In the fuel pressure/flow section of the Flight Manual Supplement (FMS) it describes the old fuel pressure gauge (no longer available) that was part of the Bendix kit. As I have an EDM-900 my fuel pressure and fuel flow readings are contrary to what is descibed in the FMS. This will require coordination with the Aircraft Certification Office (ACO) for the required changes to the FMS.

Any time you have a major deviation from an STC you must get approval. As I am using the original STC as data, I must get approval for the different part number components I'm using, and any other major changes. Changes to a FMS are considered a major change.

 

[mike mcs repair]

Thanks, the bigger deal though, is that his no carb heat temp is higher than my full carb heat temp ever is...

sj

first, verify the wires are not reversed on the temp prob then.... you can just dip probe it in some hot water

 

[mike mcs repair]

The original STC's (SE1CE and STC 108CE) instructions call for the complete removal of the priming system. This is noted on the Flight Manual Supplement (part of the STC) in the Normal Starting section. In the fuel pressure/flow section of the Flight Manual Supplement (FMS) it describes the old fuel pressure gauge (no longer available) that was part of the Bendix kit. As I have an EDM-900 my fuel pressure and fuel flow readings are contrary to what is descibed in the FMS. This will require coordination with the Aircraft Certification Office (ACO) for the required changes to the FMS.

Any time you have a major deviation from an STC you must get approval. As I am using the original STC as data, I must get approval for the different part number components I'm using, and any other major changes. Changes to a FMS are considered a major change.

if you are getting a field approval, then you are getting a FIELD APPROVAL, and just using the STC as data.... was easy years ago when i did it...(but many things FAA wise were easy then ) good luck

 

[sj]

first, verify the wires are not reversed on the temp prob then.... you can just dip probe it in some hot water

The formation of carb ice has confirmed the proper operation of the probe :help

 

[sj]

Ok folks, how do you insulate the crossover tube? I'd like to give it a shot!

sj

 

[stewartb]

My balance tube has the large expansion tube across the front. That part of the tube is wrapped with one layer of silicone fire sleeve which appears to be identical material as the induction rubbers. No visible fiberglass or mineral wool blanket. It's held by a couple of worm clamps. My crankcase vent tube uses foam insulation held with zip ties.

Fire sleeve fabric would be good if you can find it. This stuff with velcro? Better yet.
http://www.gwh-firesleeve.com/product/fire-sleeve-velcro/
http://www.americanfiresleeve.com/aerospace-firesleeve-with-velcro-considerations.html

 

[skywagon8a]

Ok folks, how do you insulate the crossover tube? I'd like to give it a shot!

sj

https://www.lowes.com/pd/Frost-King-0-75-in-x-6-ft-Foam-Plumbing-Tubular-Pipe-Insulation/3130471
This is the same stuff that Cessna uses on the breather vent where it's exposed to the cold air above the cylinders.

 

[OLDCROWE]

Ok folks, how do you insulate the crossover tube? I'd like to give it a shot!

sj

You getting tired of the flying icemaker?

 

[Dave Calkins]

https://www.lowes.com/pd/Frost-King-0-75-in-x-6-ft-Foam-Plumbing-Tubular-Pipe-Insulation/3130471
This is the same stuff that Cessna uses on the breather vent where it's exposed to the cold air above the cylinders.

Pete, that is not the same as Cessna stuff. That Lowes stuff is open cell and not high temp. I tried to use it and it kindof melted.

Cessna stuff is a closed cell product with higher temp resistance. fyi

 

[mike mcs repair]

You can also wrap asbestos or whatever is newer version and coat it with sodium silicate to harden it to shape.

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