I've read through 43-13 and can't seem to find any information on how to determine the need for a backing plate or a doubler unless you're looking to repair damage. Nothing on preventing damage with new installations. So here are a few example questions, and any extra info you guys can provide about sizing doubler plates would be amazing. Thanks.
1. Battery suggests mounting directly to the firewall stiffeners. This is assuming a full weight lead acid battery. Can you get away with a doubler only to mount a lighter lithium battery to the firewall?
2. I'm planning on running a 1.5 quart oil accumulator mounted on the firewall. Weighs probably the same as a lead acid battery. Do I need to add extra 3/4 x 3/4 x 0.63 stiffeners to tie these mounts into, or will a double plate suffice? How do I determine the size required for the doubler plate?
3. What other firewall penetrations require doubler plates? Why do the fuel and brake fitting passthroughs get them but the control cable eyelets not require them? What are the determining factors for load before one becomes required?
1. Battery suggests mounting directly to the firewall stiffeners. This is assuming a full weight lead acid battery. Can you get away with a doubler only to mount a lighter lithium battery to the firewall?
2. I'm planning on running a 1.5 quart oil accumulator mounted on the firewall. Weighs probably the same as a lead acid battery. Do I need to add extra 3/4 x 3/4 x 0.63 stiffeners to tie these mounts into, or will a double plate suffice? How do I determine the size required for the doubler plate?
3. What other firewall penetrations require doubler plates? Why do the fuel and brake fitting passthroughs get them but the control cable eyelets not require them? What are the determining factors for load before one becomes required?