Thanks for a great site.

I want to make sure I know how to use the APM, I have lots of questions but your brief answers will be a big help.

The aircraft is a 4m glider with electric power and will be used for movie photography.
The weight will be about 13 to 14 pounds.

It will be controlled through a duplicated 900MHz data link, part of my aircraft electronics will produce servo pulses to interface with the autopilot through the in built channel assignments of,
1 = Ailerons
2 = Elevator
3 = Throttle
4 = Rudder

I will use the default channel 8 for multiplexer switching and assign the mode switching to say channel 7.

My system will take care of navigation, etc, I just want the APM to stop the aircraft from falling out of the sky.

I plan to only use FLY BY WIRE_A.
That is - “The autopilot will hold the roll and pitch specified by the control sticks. Throttle is manual. The plane will not roll past the limits set in the configuration of the autopilot.”

So the autopilot stabilises the roll axis using the ailerons  (required roll angle input on channel 1) and the pitch axis with the elevator (on ch 2).

1. Is the rudder controlled manually with no added yaw axis stability coming from the autopilot?


2. Can I use the rudder for turns (via input on channel 4) and use the ailerons (via ch1) to independently adjust the angle of banking?  I assume I should set RUDDER_MIX to zero.

So can I use rudder and ailerons to do a banked turn if I want to just go to a new location, and then hold the aileron deflection at zero and use rudder only to do flat turns while filming so the view below just turns without producing a change of the horizon?


At a low speed with full up stick the aircraft could stall.

3. Does the autopilot prevent that situation by reading the airspeed sensor and controlling the pitch and throttle to prevent a stall, or does it detect the stall after it happens and then recover from it?
The stall airspeed will be about 10m/Sec.


PPM Multiplexer Failsafe
“When the PWM pulse width on the last channel exceeds 1750 microseconds the multiplexer switches to manual mode so that the lower 4 channels are controlled by the RC inputs rather than by the autopilot.”

4. Is it as simple as that, can I send greater than 1750 uS to ch 8 to switch to manual control and then reduce it to less than 1750 uS to return control to the autopilot which will still be in FLY BY WIRE_A mode?


I’m thinking that I should buy the ArduPilot soon so I have plenty of time to develop the interaction of the overall system.

The electronics is progressing ok but there's still a lot to do and I won’t start the airframe rebuild until I know the size and shape of the electronics and camera.
With my limited time the aircraft won’t be flying for about 9 months, probably even longer.

 5. Are you planning any changes to the hardware that I should wait for, or do you have a policy of having a mature hardware and are now only developing the software?

Thanks very much for any help you can give me,

Bill