Well, I’ve done it now.
I bought the most perfect Harmon Rocket II in existence and now I’ve modified it. They say the definition of perfection is when, if you do anything else, you make it worse, not better. As Jack Cox said in his December, 2003 Sport Aviation article, David Howe’s 2002 Silver Lindy winning HRII comes as close as you can get to perfection.
I agree, and that’s why I bought it! But 2002 is a long time ago and it’s light years ago in terms of avionics. The panel consisted of a King KMD 150 GPS, a King KLX 135A, and an Apollo SL 70 transponder. It used an EchoUAT for ADS-B. All the radios were state of the art and very high dollar in 2002, but were a bit long in the tooth as compared to modern equipment.
I’m a tinkerer and sort of a perfectionist at heart, so I just couldn’t help myself and jumped in for an upgrade. My work is ABSOLUTELY NOT a knock on David Howe, the genius who built the airplane. There is absolutely NO WAY I could ever match the work he did. It was just time for a refresh and my ultimate goal was to Do No Harm, as the doctors say.
It started about a month ago when I promised myself that ALL I was going to do is install the GMU11 in the tail and run a wiring loom to the panel. A daylong project at most… maybe just a few hours. Hah.
David ran a clear PVC tube from near the pilot’s control stick to the back of the plane. I started with a fiberglass wire fish rod, but it hung up somewhere along the line, so I started taking floor panels out. Before I knew it, I had the entire interior removed. David is well-deserving of his “HFS” moniker. It stands for Hell for Stout. After removing about 627 #8 screws holding down the floorboards, I came to appreciate and understand the HFS designation.
At this point, I decided, it would be a waste of time to remove the interior again in a few weeks to finish my “little” radio upgrade project, so I dove in with both feet. Heck, it’ll take me a week, maybe. Hah.
What followed was a series of “Well, I’m here, I might as well [blah, blah, and infinitely more BLAH]…”
The CAN bus made its way right past the elevator bellcrank behind the baggage compartment, so I wired up the plug for a Garmin pitch servo and capped it for now with a service plug. From there, I made a big CAN bus and wire bundle loop near the pilot’s control stick in anticipation of installing the roll servo.
While in that general vicinity, I removed the now-extraneous ADS-B antenna. The SL70 was due for a transponder cert, so I might as well go ahead and install the GNX 375 I had sitting on the shelf. No sense in spending $$ for a transponder cert when it’s going to be replaced, after all. Heck, I’m *saving* money by installing the 375, right?!?
I had two G5s sitting on the shelf, so it only made sense to get rid of the vacuum system by removing the old DG and AI. The only problem is that I have already installed the Garmin G5 mounting plate in my unfinished Glasair panel upgrade project. I’m too cheap to pay for a new Garmin mounting plate, so I made my own.
I wanted TAS, wind readout, and Density Altitude on the G5, so I needed a GAD 13 aaand a new temperature probe. The 375 needed to talk to the G5s, so I needed a GAD 29. I lost my comm when I removed the KLX 135A, so I bought a 205x. I never liked relying on my iPhone for navigation and traffic, so I bought a used Aera 660 and hardwire harness for a GPS display. I bought an Airgizmo 660 mount, but it was 1/4” too tall to fit into the existing hole, so I fabricated my own mounting bracket and bezel for the 660.
Then comes the wiring…
Everything [can/could] talk to everything, so there’s Airinc 429, RS-232, CANbus, and Bluetooth to consider. On top of this, I needed to add LEMO plugs to the headset plug panel, so that required a minor bit of fabrication. Believe it or not, *almost* everything worked on the first try!
Among the lessons learned:
(1) Configuration Modules are not optional. I thought all they did is act as an external non volatile memory chip to save your settings in case of a radio swap-out or hard reset. Oh contraire… Install them. My issue is that I bought both the 375 and the 205x used and ended up with only 1 configuration module between the both of them. To make it worse, the configuration module I had was defective out of the box. Of course my warranty expired several years ago and Garmin G3x support was zero help. I ended up calling Jason at Aerotronics—where I bought all my Glasair radios 6 years ago—and he hooked me up with one config module. I bought another one off an eBay seller. Both those modules fired right up and solved my problems.
(2) All the various RS-232 output formats aren’t available on all the GNX 375 RS-232 channels. MapMX and Connext are only available on #1 and #2. My initial wiring harness had something connected to #4 because “why not” rather than splicing 2 into 1. Ended up doing a window splice or two.
(3) Make the darned wiring harness longer! I really shot myself in the foot by making my wiring runs exactly long enough. The pros leave a service loop. I’ll do better the next time.
And speaking of the next time, I’ll have plenty of practice. I now have 3 planes and I have grand plans for full Garmin systems in all 3. The Glasair is well underway and is pretty much down to wiring. When my checking account stops smoking, I’ll finish the upgrade on the Rocket by adding autopilot servos, a 507 autopilot control panel, and a 10” touchscreen. In the meantime, I’ll work on finishing the Glasair because that shouldn’t cost me much because I already own all that stuff. When all that dust settles, I think it would be really cool to treat my wonderful little 1998 RV-3 to a full Garmin upgrade.
Exactly a month later, it’s finished and I’m ready to go taxiing and calibrate the magnetometer. Here are some photos of my recent work.
The original panel as of the time I purchased it.
GMU 11 where the VS and HS come together under the fiberglass fairing.
Floorboard removed under the pilot seat.
My homemade G5 mounting plate.
My homemade mounting bracket for the Aero 660.
New headset plug panel.
Behind the panel before the Halon bottle and electronic ignition box were installed.
The finished product.
