Cabin heater- dos/don’ts, pros/cons

[danny_galaga]

If i were to design a cabin heater to go in a kit plane what are some of the things I should be aware of? Are there any legislative requirements? Common sense things I should do, or not do?

 

 

[Yenn]

the usual place to get the heat from is a muff around an exhaust pipe.

 

Make sure the pipe is sound, so that there is no risk of exhaust gas getting into the system.

 

The muff is usually metal bent to exhaust pipe plus  about 20 mm diameter.

 

Run some coils such as springs around between ex. pipe and the inside of the muff. that increases the hot surface.

 

Make a pick up and exit pipe work for the muff with controlling valve.

 

Make a fireproof pipe through the firewall, with flexible connecting pipework from muff to the outlet in the cabin.

 

The main thing is to design the system to prevent exhaust gas getting into the cabin.

 

 

[Downunder]

My cabin heater comes from the rear of the coolant radiator....

 

 

[danny_galaga]

Yenn, exhaust heaters give me the willies! It would be a damn simple solution but I think I would only do it if it was something along the lines of aircooled VW's. The pipe that has the shroud around it is encased in a cast alloy heat sink. 1) it radiates more heat into the shroud 2) even if there is a hole in the exhaust, it is encased by the heatsink. Problem for a plane is that it is quite bulky and heavy

 

 

 

[kgwilson]

Simplicity and keeping weight to a minumum is why the chamber around the exhaust is pretty much the standard with air cooled engines. There is only one real risk and that is exhaust gasses finding their way into the cabin. Usually this only happens after a considerable period when there is a crack or some sort of leak develops in the exhaust system. This is why you need high quality CO detection which is audible and visual. If your engine is water cooled a radiator is the main option but weight is the problem with extra ducting pipework etc

 

 

[Yenn]

I comp;etely forgot that the cabin heater I built for my plane takes its heat from the oil cooler. Probably forgot since I have never used it, due to its never being cold enough.

 

Taking off from the coolant is even better, but there is only Rotax 4 strokes and a very few experimental engines to suit that system.

 

 

[danny_galaga]

Ha! That’s funny you forgot 

 

when end you have used it did it work ok?

 

 

[Diddy Pilot]

In designing the cabin heater, don't forget to think about the the cockpit layout.  

 

In some aircraft, including the Gazelle the Cabin Heater and Carby Heater are located right next to each other; similar looking push/pull knob.  This increases the risk of selecting the wrong control or at times of heightened awareness/activity such as when landing at an unfamiliar airfield a quick glance to check that carby heat is engaged is confused.

 

I would ideally locate them on opposite sides of the panel.

 

 

[danny_galaga]

Good point. What about vents? Would they be better near your feet and whatever hot air makes it higher is a bonus or better in the panel? 

 

 

[pluessy]

I have used the cabin heat many times in my Tecnam, main reason is to keep the windscreen from fogging up early mornings with high humidity. The Tecnam has a small outlet at the feet and the main one at the bottom of the windscreen. By the time I have done the engine run-up, I have 2 small patches where I can see through and at lift-off, most of the bottom 1/2 of the screen is clear and the rest clears up within a minute or so.

 

 

[pluessy]

Just returned from a short trip Narrabri-Glen Innes and back. It was 1-2deg at 7,500', so the heater was on all the time. Glad I have it.

 

 

[danny_galaga]

How does the tecnam cabin heater work? I fly a tecnam at the school but I’ve never actually looked 

 

 

[pluessy]

air intake under the prop (round hole), then flex duct to the heat muff on the exhaust muffler, from there another flex hose to the valve on the firewall (bottom left on the P92). The flap directs the hot air overboard (out the bottom) when closed and through the firewall when open. Inside are a couple of smaller flex hoses directing the warm air to the 2 vents on the instrument cover and there is a small outlet in the feet area. Pretty standard for most aircraft.

 

 

[Old Koreelah]

Danny I'm with Yenn on this one. Any air that passes the engine and exhaust should be kept right away from your cockpit. 

 

Carbon Monoxide can kill you; don't trust those silly colour-change cards. (The first sense to be affected by CO is your colour vision...) Household digital CO detectors with a ppm readout and loud alarm are not expensive and can be fitted anywhere in your cabin. Mine has its own 9v battery, which lasts for years. The only issue is longevity. I have read that some detectors may need to be replaced after a few years.

 

I relocated my oil cooler so that it had a separate inlet and its outflow could be diverted into the cabin. It worked a treat, but it was in the wrong place and didn't cool the oil enough, so I went back to the old setup.

 

If you rug up and control the draughts, you may not need a cabin heater.

 

 

[danny_galaga]

Interesting. I am actually thinking of using the oil cooler so it’s nice to know someone else has done it. In my case I have an idea that the cooler will stay put but I will have a vent behind it that captures the hot air. The handy thing about that set up (if I can make it work) is the vent will most likely slightly reduce the cooling capability of the cooler but only when it’s cold thus helping keep the oil temp right

 

 

[Jaba-who]

I don't have a heater and never really considered it before but I'm noticing the cold more these days. 

 

I've  always been very wary of venting any engine bay air into the cabin. 

 

But was thinking maybe a flexible hose wrapped around the muffler might work and if the inlet of the hose were outside air. 

 

But I guess the air flow might be too fast to heat up. Have to have a rapid heat transfer. 

 

Does anyone know if you can get metallic  corrugated tubing may an inch and a half diameter or so that would wrap tight enough? 

 

 

[poteroo]

After hearing 1st hand about 3 pilots nearly losing control due to CO poisoning, I don't trust heaters. Never use them myself - only for the bride who feels the cold. In that case, I direct outside vented airflow towards my face, but at a low enough velocity to not 'open' my boom microphone. (windmuff on the mic helps too).  I have, (but don't rely on), the standard CO detector but replace frequently.  happy days,

 

 

[Roundsounds]

After hearing 1st hand about 3 pilots nearly losing control due to CO poisoning, I don't trust heaters. Never use them myself - only for the bride who feels the cold. In that case, I direct outside vented airflow towards my face, but at a low enough velocity to not 'open' my boom microphone. (windmuff on the mic helps too).  I have, (but don't rely on), the standard CO detector but replace frequently.  happy days,

I’ve had two CO events due leaking exhaust systems, even with the heater off gasses can make it into the Cabin. I had the LAME disconnect the scat hose between the exhaust muff and Cabin heat inlet and vent the hot air overboard. Trust me, you’re way better off rugging up in sensible clothing. Not nasty synthetic materials like nylon, but material to provide best fire survival properties and gloves, scarf etc.

 

 

[Yenn]

Why risk a fire by putting flexible hose in close proximity to an exhaust pipe.

 

You make a box around the pipe and a connector for the flexible line to the valve and then cabin.