I've built an X8 with retracts, my Apm 2.5 is set up for elevon mixing and my left horizontal transmitter stick controls the nose wheel steering (rc channel 4). Am I going to be able to set the autopilot up to control the nose wheel during auto take off without writing code or will I need to write this myself?
I'm no expert at this, but with the autotakeoff feature in arduplane ( since 2.60 ) , it relies on it being a taildragger, in as much as it expects the the tailwheel to be attached to the rudder, and it expects to be able to "climb out" at the takeoff attitude.
So, in your case, If you have your front wheel connected and configured like its a rudder channel, ( since the X8 has no rudder ) , then you should at the very least be able to get it to properly steer when on the ground, before takeoff , if you tune it right.
The only other matter is whether of not the X8 needs to be actively "rotated" on its mains ( by action of the elevator/elevon ) or if it is passively able to takeoff without any other specific input. I would suggest that if you trim the X8 so that it climbs at maybe something like a 10% climb when at full throttle, then it should be able to "climb out" of the takeoff.
Just remember that because there's no actual rudder to steer the plane during the transitional period, immediately after the nose lifts, and before full takeoff, the X8 is basically unsteerable, so it's quite possible unless the front wheel PID is tuned *really well* to ensure a very straight takeoff that it may go horibly wrong.
Thanks for the info Buzz.
I'm wondering now if I should fit some micro servo's and cut small rudders on the vertical stabilizers. I have thought about it before, may help with getting out of a flat spin too, I've seen a few x8's stuck in flat spins.
You mention that the apm is setup for tail draggers - it sounds like I would have to reverse the rudder channel when under auto pilot control and put it back to normal for manual mode. I'm guessing that would be a software modification?
I cant say yet if it will need an active rotate on the elevator - my best guess is that it wont. By implication then - the autopilot does not apply, at a set ground speed, elevator during auto take off?