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Avionics page 2...

Installing New Avionics

My installation was a bit different in that I had all local resources to do the work. It takes more time than you think to draw up all the interconnections and think through the Avionics interconnect HUBdesign. When I went to get FAA approval at the local FSDO, it was the first time they had seen the GA use of an avionics hub from Approach Systems, but with the technical data sheets for the product, I got approval.

I installed the HUB against the firewall as there really wasn't any other place for it. Cables from all avionics plug into one of the ports.

Factory-made cables connect avionics to HUBHere you see the factory made cable bundle that connects the Garmin GMA 340 audio panel to the HUB. The 2nd cable with the loose wires connects to the headsets, etc. A separate cable connects the Garmin 530 to the HUB as well. A master wiring diagram of the HUB shows all the interconnections to the other ports so if you need to make up a wiring harness -- for the Argus, for example -- you can choose which RS-232 port to use and wire the cable to its designated pin.

Box Swapping: It's mid 2009 and I'm thinking of swapping out the steam gauges for maybe an Aspen Avionics EDF1000 Pro. I emailed Approach Systems and they have a cable system to connect the Aspen to the Hub and therefore to avionics subsystems. At this point, it's best to check their cable wiring diagrams to make sure all the options are incuded for your current installation and maybe future additions like expanding to an Aspen MFD. There are other systems available but I like the ease of installation of the Aspen. Not a simple decision.


Layout Considerations

Airframe tubing prohibits a deep radio stackIdeally, the Garmin 530 should be higher in the stack because it is the primary navigation instrument. But it wouldn't fit. A structural tube interferes with the radio backplate. So the 530 had to be lowered a bit. I understand that in later years, Mooney relocated this tube?

So I put the Garmin 330 transponder at the bottom of the stack. This works out great for IFR usage as all the buttons are right at your fingers tips and you can reach the IDENT with your hand on the throttle.

A few questioned why I retained the King KX175B radio when a Garmin 430 would fit in the same space. Two reasons really. That "coal-burning" King is still a good radio for one. Also I wanted to wait a few years in case other technology came along that was better than the 430. Also I think if I could have fit the 530/430 in the center stack, then I might have gotten both. But split apart as they were, I'll just wait and see.

A similar case arose with the engine instruments. The original instrument was an Alcor EGT meter with a mechanical cylinder selector. Nothing else would fit in that space except for a nice accurate vacuum gauge I had. With extra space on the right hand side, I had room for the JPI 700 AND the JPI 450 fuel flow. I know the fuel flow can be combined into the one unit, but I like them better separated.

JPI Comm Error

There is a bug with the JPI fuel flow and no one seems to have the answer (despite my detailed description). The JPI normally communicates its fuel flow data to the Garmin 530 so you have that data on the Garmin's Fuel Planning page. And this is does quite well... UNTIL, you switch on the Garmin 300 transponder and then all data comm ceases. But since it's really non-essential, I have ignored it.

Buy the Best Connectors

High Quality Siver connector to GPS antennaToo many times I have stuck my head under the panel of an airplane only to see the coax cables tightly bundled in a neat figure-8 and then wire-wrapped to the buss power line. Ouch! A little extra care in routing these properly will payoff in low-noise transmissions. Likewise, make sure your installer uses the best connectors you can get. Not cheap, but worth every penny. I saw in my own plane where -- instead of using the proper connector -- the coax was bent through a tight 90 deg angle.

Likewise, all ground avionics grounds should be routed to a common point. If you have a fiberglas belly, make sure metal plates (ground planes) are installed to the transponder and DME. Audio jacks must likewise is insulated from the aircraft frame. In my old installation they were NOT and I could always hear in the headset the strobes firing. Wired the new ones properly and when I switched on the strobes for the fist time I thought they weren't working; NO NOISE!

Flight Tests

This is the fun part. The hard work is behind us. The exact parameters are described in the installation manuals but basically you are looking for any weak points in the setup; The GPS antennae can be shadowed by the wings or rudder during steep turns, interferences develop due to harmonics between systems leading to reception weakness or error so you will broadcast on certain frequencies while monitoring GPS reception. You want to know now in good weather that the system performs within specs. And also you will check for repetition error; flying over the same point on the Earth from different directions must show up as the same point on your moving map. Transponder will also need to be checked and logged.


Hope this was of some help in your decision to upgrade your avionics. If I decide to replace those old Steam Gauges, I'll document it here.

Also if you have any detailed questions, email me from the link on the front page.

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