Since I live in New England, having effective heat in the airplane will be important to me. As I was reviewing the updated fuselage manual for the Sling TSi, I noticed that TAF updated the cabin heater design, from a system that uses ram air flowing through a cuff over the muffler, to a system that uses a heat exchanger coupled into the Rotax cylinder head water coolant loop – which is the same approach used in cars. I think this is a much better design, and greatly reduces the possibility of carbon monoxide and other exhaust gases coming into the cabin. I also think it’s important to be able to send warm air onto the windshield to clear fog.
After a bit of sleuthing, I believe I’ve found the unit that TAF sources, a Siroco Tenere Performa 4D heater. I have an email into TAF to see if they’ll sell the parts to me to put this into my Sling 4. I’m also considering coming up with something on my own. This box weighs about 4 pounds, uses 80W for the blower motor, and will supply up to 20,000 BTUs of heat per hour, which should be more than enough. But it doesn’t really have any way to direct airflow, so the TSi kit also supplies (I think) a bunch of hoses and ducts with butterfly valves to control the airflow.
I’m surprised to see there aren’t many off-the-shelf options for cabin heaters that take advantage of the Rotax engine’s water cooling system. Kitfox offers a very simple device for their planes — it’s really just a case fan bolted onto a heat exchanger. I’ve also read that Vans may have something for their RV-12. But I’d like to see something closer to what’s in cars, with dampers and doors in a blower assembly that directs airflow to your feet, face, or defroster vents.