Mooney 201 » Maintenance - Avionics page


The topic of avionics will evoke passionate emotions in any pilot. I started flying in 1970 and for 30 years it was the same old steam gages. Now every month brings a new opportunity. So what you ultimately choose to install in your plane will depend on so many variables; the budget being just one of them.

So rather than just make a show-and-tell of what I did, I'll illustrate some of the steps I went through as they might then apply to your personal needs.

Designing the New Panel

Mostly Original 1979 panel

This is what I had to start with. Basically 1979-era avionics with a few upgrades like the Argus, LORAN and a Telex intercom. I knew I wanted to remove much of the outdated technologies and install some Garmin-based systems. But, first... What if you decide to swap out radios or other avionics in the near future... maybe there is another way to simplify the installation process?

Well, turns out there is. Most avionics was always direct-wired; making even the slightest box swap a near-nightmare of wires. The folks at Approach Systems make a HUB for this purpose; think "Garmin-centric Patch Box". Suppose you have a King KT-76A transponder and you want to replace it with a Garmin GTX 330. WIth the hub system, you unplug the cable from the King, disconnect power and coax cable and plug a NEW data cable for the Garmin into the same port on the hub, rewire power, ground and coax. Since the factory cables are already FAA-approved, there are fewer local points of failure. The hub also allowed me to have a master plan and update in stages as resources would allow. In practice, I would advise doing as much at once as you can afford.

Other Considerations

Think about any other work that should be done at this time. Especially if you want a new paint job soon:

  • Removing that ADF will leave a hole in the tail where the antenna was. And a big bare spot to patch and paint.
  • You will want to replace ALL that old coax cable. Including the one in the rudder, but it means drilling out the rivets. So best to do just before a paint job. Else leave it.
  • Headliner and side panels must come out. Now's the time to patch them or add insulation to the interior skin. Plan a location for 2 GPS antennae.
  • While the panel is out, what about replacing instruments, tach cables, hoses, etc
  • Also make plans for any future upgrades like music connections, power for headsets

The Goal - A New Panel

New Garmin-centric panel

So let's jump to the finished panel. In the next section I'll look at work to install it all.

But for now I'm thinking... Wouldn't it be nice to replace those old steam gauges with some new flat panels?

(Continued on Page 2: Installing the New Avionics)