Next week we are having our first 100+ degree days this year. But in my 185 I've been having 100+ degree days since I purchased it. I know this because of the CO Guardian I installed. Among a bunch of other stuff it gives me OAT, we will call it 77 degrees, and IAT, that will be 107 degrees. The IAT comes from the back of the CO Guardian. And it is accurate cause I pulled the transponder the other day to send it in for repair and it was almost too hot to handle. If it's 77 outside I'd love it to be under a 100 inside!

So I'm looking for recommendations on the BEST firewall insulation, preferably for both sides of the firewall. What's in the 185 now is what came with it, and it is completely intact and covers all of the inside of the firewall. Of course it is 1970's technology at best. Here is a pic from when I was refurbing the cockpit.:

Phil

Have you considered an Avionics cooling fan? Might be a good thing... these things do get hot.

gunny

Gunny you bring up a good point. My assumption is the heat is coming through the firewall. But my avionics are all just one step from tube type radios, so just like incandescent lights, they could be contributing to the heat. I'll have to test that hypothesis. I'd prefer it be firewall insulation, a whole lot less expensive then modern avionics.

Next time you are up for a flight, turn off all the avionics for a while to see if they are the heat source.
Careful not to get lost though

237

If your firewall insulation is the culprit then the whole cabin should be hot.

As gunny pointed out the most likely source of heat at your avionics rack is the avionics. Installing an avionics fan is not that big a deal. Radios are sposed to get hot to a certain degree (ha!) and most handle it just fine. Remember your transponder is constantly transmitting. If your radios are truly getting too hot they'll start shutting down or you'll experience less than optimal service between radio servicing.

YMMV

Your insulation could be a tiny bit better but what you have looks pretty good. I bet all you would gain from closed cell foam or anything else on the firewall would be noise dampening.
Does that airplane have the little avionics cooling scoops on the boot cowl? Some do but most in AK are glued shut to keep the cold out.
Could your heat be partially on? Maybe the flow divider is allowing hot air in...

I had enough avionics-created heat that my panel felt warm to the touch even in cool weather, so I had my IA install a small avionics cooling fan--it's connected to the avionics master so it comes on with the avionics. My airplane is old enough that it doesn't have the little side scoops, but in our discussion, he said he routinely covers those, because if the airplane is flown through rain, it's not unusual for water to come in and damage things. I think the fan was maybe $100, installed, and it does make a difference.

Cary

Cary wrote:I had enough avionics-created heat that my panel felt warm to the touch even in cool weather, so I had my IA install a small avionics cooling fan--it's connected to the avionics master so it comes on with the avionics. My airplane is old enough that it doesn't have the little side scoops, but in our discussion, he said he routinely covers those, because if the airplane is flown through rain, it's not unusual for water to come in and damage things. I think the fan was maybe $100, installed, and it does make a difference.

Cary

Cary, does the fan exhaust into the cabin or overboard somehow? Is there some kind of baffling to help maximize the draw though the avionics stack?

This discussion has me wondering about a couple of alternative methods, too - like maybe a simple tube going to the outside that acts as a venturi to draw air from the top of the stack out... It wouldn't do much for sitting long periods on the ground in hot weather, but might work in the air.

$100 bucks is a comparative bargain when you're talking about protecting (potentially) $60k worth of avionics, though!

I haven't paid much attention to where the tubing from the avionics fan goes, so I'm not much help. I leave all that "under the panel" stuff to either my IA or my avionics guy--afraid I might hurt something or me! Sorry.

Cary