Mounting the Radio Stack

I will have a stack of four radios in the center of the instrument panel of my Bede BD-4C airplane. I installed three of them now. I will add the fourth next year. Here is my mock-up of the instrument panel. You can see the radio stack in the center.

From top to bottom, the four boxes are:

• PS Engineering PDA360EX audio panel. This is like the stereo receiver in your home. Everything gets hooked up to the audio panel and, by pushing buttons on its face, I can decide what I get to hear. It also has Bluetooth so I can listen to music from my phone.
• VAL Avionics COM 2000 VHF transceiver. This is a communications radio, for talking to air traffic control and other pilots.
• VAL Avionics NAV 2000 navigation receiver. This radio receives signals from VOR transmitters on the ground and lets me navigate either toward or away from them along roadways in the sky called “victor airways.” It also receives signals from ILS and glideslope transmitters at the ends of runways, allowing me to land in poor weather.
• Garmin GTN 650 GPS/NAV/COMM/MFD. This radio does everything that the COM 2000 and the NAV 2000 do plus it has a GPS receiver and a database of every airport, runway, and instrument approach procedure in the US. It allows me to navigate and land in pretty much any type of weather (even weather so bad that I would not fly my airplane!).

To my MGL EFIS (Electronic Flight Information System), the big screens on both sides of the instrument panel, the pair of VAL Avionics radios appear to be a single Garmin SL 30 nav/comm radio.

Here is a photo of the top three radios, laid out on the bench. You can see that they are pretty good size. The VAL Avionics radios are nine inches long and weight more than three pounds each.

I had had my instrument panel cut with a water jet by a local shop (more on that in another blog post, coming soon). That gave me a sheet of 0.063 aluminum with a single flange along the bottom to add some rigidity.

Each radio comes with a mounting tray, much like a car radio. The radios can be slid into and out of the trays, allowing them to be easily installed in the airplane and later removed for servicing.

I flipped the panel over on its face and stood the first two mounting trays in the holes. Then I added a pair of aluminum U-channels, like this:

Then I clamped everything together, drilled, and assembled with #8 stainless steel machine screws and lock nuts.

Once I had all three radio mounting trays in place, the assembly looked like this.

I attached the U-channels to the back of the instrument panel.

Next, I added some aluminum sides, which are screwed to the back of each of the three trays. The result is completely rigid and adds very little weight.

This whole assembly attaches to the instrument panel with six screws. When I am ready to add the Garmin GTN 650, I will remove the stack, add the Garmin’s mounting tray, and reattach the stack to the back of the instrument panel.

Here it is with the radios in the trays.

I spent a lot of time planning this but once I started, the whole project came together in about a week in October.