Firewall Construction

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GESchwarz

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In order for the firewall to be true to it's name I am assuming that all stainless steel firewalls are constructed using steel fasteners and steel stiffeners, if any. If we had a firewall that was attached and stiffened with aluminum, then in a fire, these supporting aluminum members would fail long before the steel sheet itself, essentially causing the firewall assembly to fail. The problem I see right now is that suppliers like Aircraft Spruce does not sell steel rivets, so I'm thinking, do people use aluminum rivets in their firewalls?
 

cheapracer

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If the aluminium is hot enough to melt you were already long dead before you need to be concerned about structural failure!
 

TFF

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Use Monel rivets. I think most do use aluminum rivets as fire would take a bunch of concentrated heat at the rivet to melt it. If you have an engine fire, you are shutting off the fuel and planning for a ditch; it only has to get you down from your altitude.
 

Turd Ferguson

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In order for the firewall to be true to it's name I am assuming that all stainless steel firewalls are constructed using steel fasteners and steel stiffeners, if any. If we had a firewall that was attached and stiffened with aluminum, then in a fire, these supporting aluminum members would fail long before the steel sheet itself, essentially causing the firewall assembly to fail.
Not necessarily. The Cessna Learning Center in Wichita, KS has a Caravan procedures trainer that was built from the firewall/cockpit section of the fire certification test airplane. Some of the aluminum structural members behind the firewall were melted/severely damaged during the test, but the firewall was not penetrated by flame(s). It passed. The certification test requires withstanding "x" amount of heat for "y" amount of time. It doesn't have to protect indefinitely.

Airplanes with a stainless firewall usually use monel rivets. However, lots of airplane were certified with a galvanized steel firewall, which likely used monel rivets and some were certified with an aluminum firewall.
 

GESchwarz

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If the aluminium is hot enough to melt you were already long dead before you need to be concerned about structural failure!
I'm not going to bet my life on that theory. Moreover, aluminum fails at about 1000 deg F, the exhaust from my rotary engine is 1800 deg F. The failure of the exhaust system, not a fuel fire, could torch an aluminum member. The stiffening members must be on the engine side of the wall, therefore they must be steel and so must the rivets that hold them. It these stiffeners were to fail it very well could cause another part to fail, and it's failure of that part that would cause a total loss of control of the airplane.
 
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TFF

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Having fixed an exhaust at a wastegate torching at the aluminum cowl for about 10 hours, all it did was blister the paint; temp probe reading 1550F. Everything is a heat sink so you would need to have the whole engine compartment above that and then the heat transfer would be so bad you would be burned from the structure behind the firewall.
 

BBerson

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Having fixed an exhaust at a wastegate torching at the aluminum cowl for about 10 hours, all it did was blister the paint; temp probe reading 1550F. Everything is a heat sink so you would need to have the whole engine compartment above that and then the heat transfer would be so bad you would be burned from the structure behind the firewall.
I fixed a large hole that an exhaust leak burned through the lower cowl of a Cessna 206.
 
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