Now we're cooking with gas!
I have just completed a project to build a helicopter with a gasoline engine, controlled by Arducopter (of course!) This helicopter serves as a test bed for future gas heli development work for a client of mine. The goal was to prove out that it could be done. Gas engines pose a unique challenge for Arducopter due to the heavy vibration they produce. But they also present a lot of promise for UAV applications as it can allow heavy payloads, long duration flight, and high speeds.
The heli is based on a Helix Heli conversion of a Trex 700. However I stretched it to 800, used many aftermarket upgrades such as from KDE, and machined a number of custom parts myself. The machine required quite a bit of customization in order to increase frame stiffness which is important for vibration reduction. The engine is a Zenoah G29RC engine with pull start. This is an increased displacement 23cc engine, which makes more power but creates more vibration than the G23. I could have purchased an aftermarket balanced engine, but I wanted to use COTS parts and also prove the Pixhawk can survive with a worst-case engine.
Last night I performed the first check flights of the new machine and began PID tuning. This is one segment of that flight where I was working on the PIDs.
Today I finished the PID tuning, and it is flying very well indeed. After increasing rotor speed to ~1600rpm and tracking in the blades, the vibrations on the Pixhawk are quite good, better than both of my quads:
I flew it around a bit in Stabilize, and hit 30 m/s without really trying. It should easily be capable of 40 m/s flight speeds. I'm hoping for a 10 kg payload capacity. Flight time is currently better than 20 minutes with plenty of reserve on a 630cc tank. I will probably begin development on a larger fuel tank system on the order of about 2L which should allow for 1 hour of flight time with payload. Currently the 2S 4400mAH avionics battery lasts for at least an hour, but will be supplemented with an on-board generator.
Later today, I will start working on auto missions and will shoot another video.
The success of this project opens up an entirely new world of possibilities for affordable UAVs. It will be possible to perform realistic crop spraying. Aerial imaging with the best quality cameras available. And extended flight ranges in a large aircraft with VTOL capability for usage in areas without a prepared landing strip. Obviously this is not the type machine that would be used anywhere near people. But remote areas, or secured industrial lands would be suitable operational areas.