Avionics

My foremost commitment on this project was to weight reduction - increasing performance through reduced weight. The TFE731 conversion requires adding a minimum of N1, N2 and TIT to the L39 dash. Some have used the original (Hawker, WestWind, etc.) gauges to support these functions. Other installations have used things like the EI's stand alone engine instrumentation. Both these approaches requires the installer to "push" additional equipment into an already crowed L39 cockpit environment. The alternative for me was to literally remove just about everything from the L39 cockpit and replace it with a modern high density high functionality avionics suite. There are a lot of very capable offerings to the Experimental market. I picked the Garmin G3X solution as it was cost competitive and most likely recognizable to pilots familiar with jets.

The G3X installation provides 2020 ADSB in and out compliance, traffic, terrain and synthetic vision. All but the GTN650 certified navigation source are remote mounted which allows both front and rear cockpits access to almost all functionality. Below are some pictures of the integrated cockpits using the G3X Touch 10" displays. The G3X also supports a robust linked autopilot so pitch and roll servos were included with the system. Anyone that has tried to hold altitude in an L39 going cross country will appreciate this feature.

Version one used a lot of the original L39 cockpit wiring for gear, flaps, trim and ACM functionality. Version two will only retain the stock wiring in the wings that support gear, flaps and trim along with the stock wiring in the nose to support NLG. All other wiring will be light weight aircraft Tefzel wiring and the remaining L39 relay and diode boxes have been replaced by a single printed circuit board with modern aircraft relays and surface mount diodes. This one board contains the brake circuit, WoW gear related circuits and the trim priority elements. In addition, the stock latching flap button system has been replaced with a microcontroller controlled board to reduce weight, improve performance and allow for landing flap auto trim amount to be programmable (to stop full flap over pitch trim with a lighter UltimateL39 and a further aft CoG). The N1/N2 signal conditioning circuits have now both been done on the same board. See pictures below.

The second revision of the Diode/Relay board is in and fully populated. This board replaces the L39 chassis diode and relay boxes in their entirety making the wiring simpler and easier to install and maintain.