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Old 10-25-2017, 08:40 AM
DanH's Avatar
DanH DanH is offline
Join Date: Oct 2005
Location: 08A
Posts: 10,948
Default Firewall Insulation In VAF Front Page Photo

Yep, a beautiful panel. With the airplane apart, it was also an opportunity to remove the fire transfer material from the inside of the firewall.

It's hard to be sure just by looking at a photo, but the material appears to be common heat/AC duct wrap, a fiberglass batt with an FSK radiant barrier.

The glass fibers are tacked together into a batt using a very light application of adhesive. The FSK radiant barrier is typically 0.003" aluminum foil glued to a kraft paper backing which contains fiberglass threads for reinforcement. The foil and paper barrier is then glued to the fiberglass batt.

This material has a fire rating...flame spread, smoke, etc. However, it is not fireproof, and it will smoke. Why? The glass fiber and aluminum foil are harmless enough, but the kraft paper and all the adhesives are not.

This is Orcotek ( cabin wall insulation as used in airliners, a fiberglass batt enclosed in an aluminized film. It's legitimate aircraft quality stuff, but it is not intended for application to a firewall...and neither is AC duct insulation:

OK, now let's set aside all the fire and smoke concerns, and simply ask "Is a good way to insulate?" The answer is "No".

First, it's called a radiant barrier for a reason. It's purpose is to prevent attic heat from warming the air flowing inside an AC duct. Although it has some value in blocking conducted or convective heating, it's real purpose is to block radiant heating from all the hot materials in the vicinity, like the inside surface of your roof. That's why it is installed with the shiny aluminum foil surface facing the heat source. Here it's installed bass-ackwards.

Second, placing the insulation on the inside of the firewall is like wearing your raincoat inside your clothes. You're allowing the airframe components to heat, then trying to block that heat from reaching the air space inside the airframe. It's simply ineffective as a comfort insulation, and in the event of fire, it does nothing at all to protect the airframe.
Dan Horton
Barrett IO-390
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