Firewall heat valve box material -3/-4 ??

[Larry DeCamp]

The Vans firewall heater box & door is aluminum. My archive search did not clarify why aluminum is OK when there is is so much concern expressed about fire resistance regarding other firewall penetrations. Forgive me if I missed something, but why is Aluminum OK?

[brad walton]

I think it may have a stainless steel flapper. But you are correct that it should be a concern. I bought an all stainless steel one from Aircraft Spruce (IIRC)

[BillL]

Originally Posted by Larry DeCamp

The Vans firewall heater box & door is aluminum. My archive search did not clarify why aluminum is OK when there is is so much concern expressed about fire resistance regarding other firewall penetrations. Forgive me if I missed something, but why is Aluminum OK?

"OK" is conditional based on what you consider fire protection. It just depends on how much risk is "OK" for you. DanH has additional protection with an insulating barrier on the forward side of the firewall based on his knowledge/experience, and has done an excellent test program to back up his decisions.

I watched the video of a fire test with the aluminum box and decided to get the stainless heat box for my 7. It is a big hole if fire gets to it. I am not insulating the firewall, but have high temperature pass throughs everywhere. Is it "OK"? I don't know, but if needed, I will drop the engine and install a stainless foil covered insulating barrier like Dans.

There remain thousands of aluminum boxes out there and I personally don't know where one contributed to a catastrophic event. So, as always, YMMV.

[az_gila]

Originally Posted by brad walton

I think it may have a stainless steel flapper. But you are correct that it should be a concern. I bought an all stainless steel one from Aircraft Spruce (IIRC)

Nah... the flapper is aluminum like the rest of the box...

[rzbill]

No reason to change the box to stainless. Just scrounge a small piece of stainless for the door and get a steel hinge.