Who here has built an sUAS with internal combustion engine? What are your general recommendations for cruising, reliability, and avoiding an engine-out situation, etc, etc. I have a 10cc RCGF I want to install in a Tucano. I think it would be a killer setup. I’m still earning my wings on electric, but gas power sUAS looks to be the final frontier. Spill the beans!
I prefer ICE’s … I just removed a 20cc Rcgf from a 90" cub and replaced it with a saito fa82 glow engine. I don’t like 2 strokes because they are risky at low rpm…
If you are running a 2stroke, especially a smaller displacement (under 50cc), set the minimum throttle to somewhere above idle but low enough to allow the plane to slow or stop on landing (unless you what to switch to manual to slow to idle).
Also, be careful about letting the autopilot apply throttle too fast. Set the throttle slew to as slow as you can and be confident the plane will work. Different engines can take different rates, but I like 33% (takes 3 seconds to go to full throttle). My cub nosed-in after a landing abort resulted in the engine dying …after I increased the throttle slew.
I also saw the engine die after an automission takeoff level-off and turn to the waypoint…I think the mission would actually throttle back, then increase as it read the next waypoint coords.
So, just be careful about allowing the auto modes to take the throttle too low or increase it too fast.
I also fly rc planes without autopilots, and I am amazed at how much longer a tank of gas/fuel lasts with autopilot in automissions… I like my cruise speed set to a speed that is safely above stall, but not ‘fast’ for the airframe. User preference. I believe that’s the most efficient speed to avoid drag losses and wasted fuel.
I still get nervous about “engine-outs”, but multiple missions without incident help calm the jitters…or confirm my fears! I REALLY prefer 4 stroke engines over 2 strokes because of this reason. I found the same issue when I rode dirt bikes.
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10cc gas is really small. Good luck with that. Those tiny gas 2 strokes are the hardest ones to tune and get to run reliably.
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There is another trick you might keep in mind to avoid deadsticks… A heavier or slightly larger prop than normal can act as a flywheel weight and help keep some smaller, finicky engines from quitting so much. Be careful with this, especially if the prop is oversized, as it is more load and will generate more heat in the engine when at higher throttle settings. If you try this, set your max throttle to somewhere lower than 100% - the autopilot will go to max throttle setting to climb.