After long trial and two different versions of it, I completely finished my RMU. The first time I just tried to make it almost similar to the real Honeywell gauge, just concentrating my efforts in making it clean and functional. Anyway after I had completed it I felt that it wasn’t really what I expected to realize, even if it was nice looking and, as you could have seen in the video in a my previous post about the center MIP, well realized. So I started from scratch and with the data obtained in the first run I focused on the many details present in it, overlapping real images to my drawings to find the one and very harmonic feeling it has. Aircraft parts are not only functional but nice looking too… Now I have to say that I’m proud of it. It’s really a small piece of italian art!
The very first consideration to have is that in cockpit building we can’t really make things like in a real aircraft and someway this makes things really more difficult. We have to find solutions to make our sim objects the most close to the real ones. In this case, the real RMU has an it’s own display in it and a lot of space in the back to work with keys, electronic boards and backlighting. As I’m going to use a monitor instead on the back of the MIP shared with many other functions the working space shrinks a lot and the max I could obtain to stay in the limits of a real object was 12mm total thickness… Yes, I had to make a piece that in just 12mm thickness and about 120×110mm size would contain a full plastic housing with a front and back, a PCB to hold components (20 keys), a backlighting system driven by leds or wheat bulbs, the keypads and let’s not forget the rotary encoder with pushbutton or even a dual rotary encoder like in the real one. It sounds like… Engineering… 
I approached the problem by working in slices and trying to strengthen the structure everywhere I could to make the panel rock solid even if the front plastic bezel is in many points just as thick as 0.6mm to allow keys to stay under it and still have some free space to actuate them. The PCB in this piece is 1.5mm thick, but I’m going to change it for a 0.8mm one in the next runs. This won’t help the front keys part but will leave some more space in the back of the PCB itself for wiring that actually needs very small section wires.
The panel has a total of 25 inputs to use and I arranged them in groups of 9+1 ground for opencockpits ready connection. As there were not enough space in truth to also hold an FC connector on the back, but If I would go to let some space between the back MIP and the monitors, I managed to make a breakout board that actually order the inputs as well and allow a straight connection to the mastercard without problems… Plug’n'Play!
Also a pot connection has been planned to dim the light inside the panel and a real light sensor could be added to autodim it depending on light conditions.
Having had the TQ plate allowed me to also make a custom paint matched with the real color. I have to say that the paint used in the L45 is a really matte one and without any type of reflection even in presence of direct sunlight. I’m sure they used an extremely expensive coating. Such a matte color can’t be reproduced even by a custom made paint so the color I got feel the very same by looking in front but has a slight different color reflection when looked at by side. Very forgettable details, but I’m looking further to find a different type of paint that can solve this little problem.
Keypads were made out of a single piece of soft polycarbonate sheet 5mm thick, formed to stay in place and give a strong tactile sensation and then coated and engraved. As I used leds for backlighting as their color is a bit in the cold side of white, I also managed to apply filter lenses on the back of them to align the output light color to the bulbs reddish one. Leds in my opinion are a better way for driving backlit panels: they drain less current and produce lower temperatures. As 14 x 3V leds are used in the whole panel, a single 1A 12V supply can light both the RMUs and even the 4 DUs that I’m going to make. As I’m always open to different solution though I also bought a bunch of wheat bulbs of various sizes and voltages to test them and check differences. When those will be delivered to me I’ll update this post with my results.
Now it’s time to load an Honeywell RMU driven aircraft and test it’s functions. I chose to give a try at Wilco Citation X too, because it’s atm the only one that has it fully functional. Another solution would be the PM Regional Jet package, but it’s a bit expensive and not yet complete. Hopefully in a short time, Jason of FlightDeckSoft will release his own package with RMU, PFD and NU, that by looking at preview images it looks really cool!
Have happy flights!
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