Jason Short came up with a great flight mode, FLY BY WIRE, in ArduPilot 2.5. This mode differs from STABILIZE. In STABILIZE the autopilot constantly tries to return the plane to 0 pitch and roll, while you give stick inputs that tell the plane to do something else. It feels a bit like you are arm wrestling against the autopilot sometimes. With FLY BY WIRE if you move the right(*) stick half way to the right then the plane will bank half of the maximum amount defined. As long as you hold that stick position the plane will hold that bank. If you center the stick, the plane will go to zero bank.
* - All references to right stick assume a mode 2 RC setup where the right stick controls pitch and roll.
That is all great! You are not arm wrestling the autopilot. You are telling it what roll you want and it is giving you exactly that roll.
But what about throttle and elevator? Jason had a scheme where if you moved the right stick then you would get both a pitch and throttle response. In 2.5.1 I have been trying an alternate scheme involving both pitch and throttle increasing or decreasing together. I am convinced that these schemes are not the best. But what is? It really comes down to user preference.
I think the two best alternatives are:
- Have the throttle remain under manual control and have the right stick up and down control pitch angle. This setup is great for tuning your servo PID gains (both roll and pitch), and is a really fun way to fly.
- Have the elevator maintain a constant airspeed and have moving the right stick up and down increase or decrease throttle from a cruising throttle. This setup is probably the ideal setup for new pilots. You can hand the transmitter to anyone and they can fly. Can't stall because airspeed is controlled. Want to turn, move the stick to the side. Want to go up or down, move the stick up or down. Of course they still have to deal with what up and down is and what left and right are while coming and going, but if you let go the plane will always take care of itself.
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