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C-185 cabin heat

Tom3holer

Tom3holer

MEMBER
Cape Cod
Hi,
I have a 73 IO-520 powered 185 and have an issue with the cabin heat.
The airtex pastic outlets on the side near the front edge of the door are discolored due to heat and were before I bought it 4 years ago.
I had noticed that during climb on colder day 20F ish it doesn't warm up much till I level off. It then heats up fine requiring the heater knob to be 2/3 the way in to be comfy.
Today I reached down and felt the airflow and was surprised at how low the volume was, with the heat wide open, but it was very hot, too hot to keep my hand close to them.
It had just come out of annual so I had the mechanic look at it and he said it was all hooked up properly. He then mad mention of the inlet which is just below the oil cooler and commented on how it didn't have much room to get a good blast of air. It was not obstructed just not much room, 3/4" maybe from the bottom of the cooler to the round inlet opening.
This obviously had been that way for some time per the Airtex plastic discoloring mentioned earlier.
Just wondering if anyone else has this issue and is there a fix/mod for it?

Tom
 
Mine 185 is the same way. Way to hot with low airflow with the heater. I open the vent to increase air flow through the heater and bring temps down.
 
Your issue may be in the flat flex duct that connects your firewall heat plenum to the outlet in your knee panel. That flex duct is old, probably been crushed a hundred times, and was never very free flowing. Disconnect it at the firewall and I bet your heat will run you out of the cabin. How does your defroster work? Pretty well, I’d guess? Better than the heater? There’s a clue.

The plumbing. Air pressure comes from the outlet under the oil cooler and pressurizes the muffler shroud. Mine works very well. Better once I lost the knee panel and that flex duct.

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aqua said:
This inexpensive kit($83) improved airflow in our 180. https://www.aircraftspruce.com/catalog/appages/airflowkit.php

Two vents go in the rear wall of your baggage compartment. One, screened, vent replaces an aft belly inspection panel. Gives the air a path to flow, front to back. The back seat gets much more heat than it used to.
Click to expand...


doesn't that defeat the whole purpose of the upper forward pointing air ducts mounted on fuselage top by stabilizer, that PRESSURIZE a Cessna fuselage to prevent CO incursion into cabin???

there's a thread on here about that subject if someone can post it....

I'd rather be cold and not CO poisoned, but that's just me......
 
Open the heat knob, open the air vent mixer some to maintain flow and heat, and close the cowl flaps to pressurize the cowling. That heated air ducting Stewart mentions under the boot cowl by the knees gets wonky and deformed so inspect that. Also make sure the exhaust flame spreader cones in the muffler are still intact or heat will be less.

Gary
 
Tom, This is the way to do it. Mix the fresh air with the hot air. You should have more than enough comfortable air. You should be able to fly in your shirt sleeves, at least on cold winter days around here.
LUCIFER said:
Mine 185 is the same way. Way to hot with low airflow with the heater. I open the vent to increase air flow through the heater and bring temps down.
Click to expand...
 
Thank you all for the suggestions.
I didn't realize the fresh air valve ran through the same plumbing as the heat. I will give that a try.
 
Tom,

I operated several 185s in Alaska for many years, including in some very cold temperatures, and never had problems with insufficient heat. I highly recommend buying a late model 185 POH for reference. Those POHs have a LOT more info than earlier ones. Not all applies, but much does. Here’s two pages from a 1985 A185 F POH for example:

9D01FDAF-EF28-4E24-8B21-5E2D33EF4D63.jpeg

D53A50E4-06C3-49BE-961E-770B2BCEFC72.jpeg

As you can see, this POH explains the process of cracking cabin air control to increase flow. your POH may not. Earlier POH were minimal.

MTV
 

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Mike mcs, I’m not familiar with the 185 being pressurized. In that case, this kit Is probably not the answer.

If you’ve seen one Skywagon, you’ve seen one Skywagon...
 
mvivion said:
Tom,

I operated several 185s in Alaska for many years, including in some very cold temperatures, and never had problems with insufficient heat. I highly recommend buying a late model 185 POH for reference. Those POHs have a LOT more info than earlier ones. Not all applies, but much does. Here’s two pages from a 1985 A185 F POH for example:

View attachment 46708

View attachment 46709

As you can see, this POH explains the process of cracking cabin air control to increase flow. your POH may not. Earlier POH were minimal.

MTV
Click to expand...

While on the subject:

The lines noted as "Adjustable Ventilators": These need to be inspected. The older scat tube that was used will eventually corrode and fail. When the scat tube fails and you are flying through clouds it will add moisture above your headliner and cause corrosion over time.

Tim
 
The vent knob lets air into the cabin, the heat knob modulates hot air from the muffler shroud.
Was up today, 5*F, vent full open, heat about 2/3. Plenty of heat.
 
It's probably obvious but there's more to the heater system than providing adequate heat.....ventilation and sufficient air flow to remove condensation on the windows is critical. Temp-dew point at any outside temp, or in cold or real cold with wet clothing and footwear the windows fog up quickly. I flew extended side bubble windows on one C-185 and they were always collecting moisture or frost. Without the defrost vent on the cowl forward vis would have been restricted. Plain heat without the air vent enabled was far worse. Some taped the upper wing-fed air vents closed in winter but i left them open to add air flow. Credit cards to scrape the ice off help as well.

Gary
 
stewartb said:
View attachment 46705
Click to expand...

mvivion said:
View attachment 46708MTV
Click to expand...

Mudwagon said:
The vent knob lets air into the cabin, the heat knob modulates hot air from the muffler shroud.
Was up today, 5*F, vent full open, heat about 2/3. Plenty of heat.
Click to expand...
Mudwagon, What you say is correct but not directly. It needs a little clarification as Tom's original question indicates there is some misunderstanding on how this system works. The vent knob opens the fresh air vent valve on the right side of the fuselage. That air is fed to a plenum chamber mounted on the aft side of the firewall. Some of the air in that plenum is dumped into the cabin directly on the front seat occupant's feet and some is discharged at floor level just in front of the doors.

The valve on the forward side of the firewall as shown in stewart's picture without the hose attached is controlled by the cabin heat control. This directs the ram air which is heated by the muffler either overboard or to that same plenum chamber and is modulated to split the flow as desired.

The comfort temperature level in the cabin is controlled by a learned use of both of those valves. The air volume is primarily controlled by the fresh air valve. Keeping the fresh air closed in the winter reduces the available volume of heatable air.

Study MTV's copy of the page from the pilot's manual. The system in the 185 is one of the best I have found in light planes.
 
Again, thank you all for the help and advice.
My 73 manual does mention modulating the outside air vent knob with heat to help in heating but no diagram which was very helpful, thank you MTV.
Had a short flight yesterday and experimented with the two controls. Adding air did increase the flow at the fwd door post and kept that air a bit cooler.
 
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FWIW the cabin heat system in the early 180's are rigged so the cabin air knob is pushed in to open,
and the cabin heat knob is pulled out to open.
It requires at least some cabin air when you want cabin heat.
From the 1957 C180 owners manual:
"never pull the cabin air knob out when the cabin heat knob is out. This may result in overheating of the heater muff hoses".
I think because the cabin air knob operates opposite from what seems logical (push to open, not pull to open),
this overheating probably happens a lot- esp with new owners.
I've even seen the cabin air knob on at lest one 180 placarded incorrectly -- as in "pull open".
 
Tom3holer said:
Again, thank you all for the help and advice.
My 73 manual does mention modulating the outside air vent knob with heat to help in heating but no diagram which was very helpful, thank you MTV.
Had a short flight yesterday and experimented with the two controls. Adding air did increase the flow at the fed door post and kept that air a bit cooler.
Click to expand...

Tom,

in all seriousness, I’d buy a late model POH. This isn’t the only example of the late model POH offering a lot more info.

MTV
 
mvivion said:
Tom,

in all seriousness, I’d buy a late model POH. This isn’t the only example of the late model POH offering a lot more info.

MTV
Click to expand...

As I recall, the 76 POH had the air vent system diagram also.

Good reminder that not just the mechanical, but the written documents also evolved.
 
OK now you have me double checking my heating techniques (I always wear long johns as a redundant system). In a 180H should I crack the air vent to increase heat flow through the system? I replaced scat tubing both from muffler and internally this last annual. I flew today around 10 to 15 degrees OAT and seemed OK and the dog was happy too.

Veteran 180H drivers have any insights here?
 
Paul...ask your dog if you should live on the wild side. Open the heater and air valves and see what happens. Experiment. Pertend you're a kid and something has your attention.

Thousands of hours at -0F here and I did the same.

Gary
 
I dress for the outside temps so in general I don't use much heat for cabin temp. The defroster is much more important to me not only to defog the windscreen but it also adds some comfort for my face, which is the only exposed skin. That's usually enough to raise the inside temp so I don't see my breath. But I don't fly much in cold temps anymore.

To me the measure of heater volume is how well the defroster works on a really cold day after a couple of people get into the cold plane and their presence ices up the windows on the inside. Especially if they're been physically active and are breathing hard. Sometimes I leave the pilot's window open to vent the cabin and promote better defroster flow. Cold weather guys know what I'm talking about.
 
On my late model 180 the heat knob controls the temperature while the vent knob controls velocity of the heat.




Sent from my iPhone using SuperCub.Org
 
Bill
Works the same on my early 1954 C-180.I doubt there is any different operation regardless of the years of 180/185's.
Lou




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