The factory aircraft has a aluminium firewall and wheel well. Certified aircraft must be protected by a suitable fire proof barrier but there are no standards for an experimental aircraft. Lack of fire protection to any recognized standard may result in a limitation's begin placed on the aircraft by the Authorized Person certifying the aircraft in Australia.
"It is up to the Authorized Person (AP) inspecting the aircraft as to what limitations they will place on the aircraft based on their assessment of the aircraft. The AP is required to issue a C of A but has to take into account possible effect the lack of a firewall could have on other aircraft and third parties on the ground.
The AP would possibly place a requirement in the Certificate of Airworthiness Annex for all persons being carried in the aircraft to be made aware of the lack of a stainless fire-wall or other more stringent conditions on its operation"
In a meeting with my AP I was advised that the builder is free to do what they want BUT if there was no firewall he would have to look at what threat this would impose on third parties on the ground in the event of a fire.
It was decided by this builder that a firewall would be a good idea from an operational point of view
Firewall
Steel is the most common selection with stainless the preferred choice having a minimum thickness of 0.015'' [FAR 23.1191]. The material chosen was 304 Half Hard supplied by Master Cut Technologies, Melbourne. The correct size material is available but it was felt the it would have not have been stiff enough.
The disadvantage is that the replaced items are 3 times the original weight in of the aluminium components.
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The wheel well was originally to be lined with Firewall 2000 Ceramic Blanket purchased from Aircraft Spruce. The weight on their site stated as 0.9 oz per square foot but when it arrive it felt like a lead vest. A check on the manufacturers data sheet revealed that the correct weight is 1.85 lbs per square foot creating a heavy and expensive ouch..!
It was now decided to replace the wheel well wrapper with stainless steel fabricated from 0.020'' 304 half hard stainless steel.
Sealing
A firewall also has another job, that is to keep as far as practical fumes from entering the cockpit. All the seams will be sealed using Permatex High-Temperate Silicone Gasket Maker [ -50C to 340C range] before installation of the new firewall.
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