The basic idea of a flight mode in ArduPilot is that changing flight mode changes the way the pilot interacts with the aircraft. So when you switch from a fixed wing stabilised mode to a hovering mode then the throttle stick changes from forward thrust control to vertical thrust control. That makes it a different flight mode.
I find this works extremely well but I do understand it is different from how some other systems handle VTOL transitions.
In plane it is settable. Just set FLTMODE_CH to 5 and it will be on channel 5. It defaults to 8 for historical reasons that go back to the APM1. The APM1 had hardware failsafe passthrough tied to channel 8 that only worked on fixed wing, so copter used a different channel.
ok, then you need to set Q_TILT_RATE to 15
you need to either re-do the accel calibrations or manually copy the calibrations over. Same for compass calibration.
The accel and compass calibrations are the same in copter and plane. I'm not aware of changes since copter v3.3.3 that would cause it to fail now and pass previously. If you persistently can't get it to calibrate then give me a tlog showing the failed attempt and I can see if I can spot a reason.
for bench testing purposes you could disable the arming checks (set ARMING_CHECK=0) but please don't try and fly it with arming checks disabled.
I've found a bug that caused the two front motors to always run at the Q_M_SPIN_ARM throttle when in FBWA. I'm guessing that is what you are seeing. I've put a new test2 firmware up that fixes that, please check that all motors now stop at zero throttle in FBWA.
* that you have a non-zero RC3_DZ
* that channel 3 min on your transmitter matches RC3_MIN
Another thing to understand is Q_ASSIST_SPEED. That is a airspeed below which the VTOL motors will provide assistance even in FBWA mode. I suggest you do the first flight and ground testing with that zero. Once you have more experience with the quadplane code you could set a non-zero value. I normally fly with Q_ASSIST_SPEED a bit above the stall speed as it allows me to slow down in FBWA to any speed I like, even completely stopped, while retaining throttle mapped to forward thrust. That won't interact well at the moment with the binary nature of the CL84, but we may be able to find a way to make it work well later.
Apart from the basic tests you have done, please perform the following tests:
* with props off, test it in QHOVER and QSTABILIZE modes and ensure it stabilises as a tricopter. Check roll, pitch and yaw.
* test that in FBWA mode you have good throttle control and that the rear motor does not spin
* while in QHOVER at half throttle (so aircraft is stabilizing) switch to FBWA mode. The fwd motors should start to tilt. As they tilt the fwd motor throttle will increase and rear motor will decrease (to maintain pitch). As soon as the motor tilt is all the way forward the rear motor should stop and you should then have fwd throttle control
* while in FBWA mode switch to QHOVER. The motors should start to tilt up. As soon as they are tilted up even a little the rear motor should start, initially at very low throttle. It should smoothly increase and the fwd motors decrease as the tilt goes up
Another critical parameter is Q_TILT_MAX. This is the tilt angle of the fwd motors beyond which the fwd motors no longer contribute to roll control. The right value for that is very dependent on the aerodynamics of the airframe. The default is 45, but it may be you need a smaller or larger value. We'll only find out by flying it.