Folks -

I'm installing the cabin heat option for my UL Power and am curious how you managed the fresh air supply for the heat exchanger.  I'm planning to pipe air to the passenger side tube on the muffler shroud as an intake, close off the middle tube, and then take hot air from the pilot side of the shroud to the cabin.

How did you guys arrange fresh air through the cowl ?



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Conor - this is extremely helpful, thank you and the picture was perfect!

Hey Conor. I don’t have any ram air on my heater at all as Roger said he didn’t think it was needed. That said, I’m not flying yet so can’t gauge how it works with engine compartment pressure alone. My question is do you think the ram air is needed at all? I’m up in Ontario so we do see some chilly weather but I can see how you wouldn’t want to much pressure on hot days with the poor seal of the butterfly valves.


Most important, make certain that you locate the heater controls where you can reach them in flight! Mine are just about an inch too far away with seat belt on.

My muff and hose set-up is the same as Conner’s except that I did away with ram intake hose.


Hi Ralph. Did you use the UL aluminum butterfly valves as well. I have them installed but worry about the fire resistance of these in addition to not having a bypass to keep air flowing through the aluminum muff.

Your thoughts would be welcome.


Yes I used the aluminum butterfly valves. That is what is available. More important question for you, can you reach your mechanical fuel valve without undoing your safety harness? Once you turn that valve off you have made the decision to land in the next, very few, minutes. Not much time to redo your harness, and you will want it tight for your fast approaching, unscheduled, landing. Fire safety should be a concern for all pilots but being a dumb farmer I probably don’t worry enough. That said I have had a banjo valve with a small gas leak in the engine compartment. Pulled the cowling off a zillion times before convincing myself that it was done leaking. I am now preparing to install the Zenith Teflon hose with steel braid kit. Complete with that orange fire stop covering. I did not know that it was an option until talking to the folks at Aircraft Specialties. They referred me to Zenith to buy it after convincing me it was a good idea. I am also upgrading most of my fuel lines from rubber to Teflon/steel braid, those will be custom made and ordered from Aircraft Specialties. I say most because the fuel tank selector selnoid has plastic barbed fittings and Teflon hose does not work on barbed fittings. Will use short pieces of rubber hose to make the transitions. It will be a couple of months before I will have that portion of my overhaul project completed.



Great advice! I have installed steel braided lines throughout and used an Andair duplex valve in easy reach. My firewall forward kit from Zenith came with the Aircraft specialty fire sleeve lines. These are very high quality. Steve there is amazing to work with and made up all my other lines to order. He backs his stuff beyond expectations as well. Not the cheapest but with fuel, you want the safest.

The only aluminium fuel components in the engine compartment are those built into the engine and the pump manifold fittings. All stainless for firewall penetrations. That’s why I was rethinking the aluminium heater valves. If the flap itself was stainless, no biggy. I still don’t like not having a continuous flow through the muff though but may just drill a couple of small holes in the end plates to accommodate minimum cooling flow.

Thanks for all the info!



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