Firewall access to electronics
 

On my RV-10, the GSU-73 is mounted high on the interior, close to the firewall. Impossible to access from inside. I believe it was built on the bench, and everything assembled around it. I need access. Is it permissible to cut a small hole in the firewall , and make an inspection plate?

Don

Not impossible to access, just difficult and painfull. I am unsure if the firewall is structural, but I would recommend against an access panel.

Larry

Before the panel upgrade I had some stuff back there. Not impossible to access, but definitely not easy. Or comfortable.

If you really need to cut a hole it is probably better to look into an access hole through the subpanel behind the instrument panel. Lots of people modify that for radios to fit, etc.

I would not even consider cutting cutting the firewall for an access panel. Remove the IP, then anything you can from there. Now remove the seats and control sticks. Law down a board and lots of pillows, blankets, or both, so you have a somewhat comfortable surface to lay on. Use good lighting and while on your back looking up, start removing whatever may be in the way until you get to the GSU-73. Its going to be difficult, uncomfortable and time consuming, but you can do it. Have a helper handy to hand you the tools as you need them. Getting in and out of your working position for tools will greatly add to your fatigue and time getting to the LRU.

I agree with Thomas.

I've got plenty of gadgets behind the subpanel and I've had to work on a couple of them. It isn't fun, but it is doable.

If you cut the firewall, you are negating it's intended purpose.

Vans (and I) would say..
 

..NO GO. The firewall, as the name implies, is very important, both thermally and structurally.

I don't think it's valid to immediately jump to the conclusion that a firewall access panel is a bad idea. There are definitely production aircraft that have them.

To do it on an RV you'd have to make sure that the structural aspects of the access panel are good and that you have good intrusion resistance in case of a fire.

Yeah, it could be done. However, I think I'd just move the offending avionics to someplace accessible. It's a one-time PITA.

Firewall
 

To name just 2, Cessna Skymaster rear firewall and Piper Malibu/JetProp have large well engineered access panels in the firewalls. To do it correctly on a flying plane sounds like a lot more trouble than it?s worth. Good suggestions in previous posts on how to work in there or move the offending box.


Don Broussard
RV9 Rebuild in Progress
57 Pacer

Firewall access
 

Yep, the Beechcraft Bonanza has ?em. There?s Fiberfrax gaskets and structural fasteners with doublers. I owned an A36 for 17 years and it was ESSENTIAL to gain access behind the panel during annuals and needed maintenance.

Lots of production airplanes out there to model them after. Go into a shop doing maintenance/annuals on these birds and take a survey......the Bonanza has been around obviously a very long time and it?s design is very well thought out. Necessity is the mother of invention.

Daryl Rosinbaum
#41627
A&P
FAC test pilot (ret)
SWA (ret)