Is there a way to program a safety kill switch for the multicopter rotors in QuadPlane? Having some trouble with the landing detection and sometimes I can’t disarm the rotors.
One option is to program MANUAL mode as a flight mode, but I’d prefer not to as it could get accidentally bumped during flight. Are there known issues with QuadPlane landing detection?
coming soon
… wouldn’t your kill switch here be equivalent in terms of lethality to
a switch for MANUAL in flight?
In answer to your question - we are getting a “universal kill switch” at
some stage soonish: https://github.com/ArduPilot/ardupilot/pull/10290/
CanberraUAV don’t run MANUAL on the RC transmitter; we force it into
MANUAL using the GCS a lot, 'though 
Also, disarm from the GCS. And if you’re keen, disarm on a switch.
The significant problem with “just go to manual” is if you were in QLoiter/QStabilize and the throttle wasn’t at minimum the forward motor is then spun up in manual. When things are going wrong and people want to just stop motors it’s hard to have the presence of mind to cut throttle first, then go manual (and arguably less safe in weird scenarios).
The method I use is to switch to Q-Stabilize as soon as it touches the ground, and then hit a switch on my transmitter that holds throttle output at 0. Any decent computer radio should have this.
Of course, if you bump it in flight, you’re going to have some weird behavior depending on which flight mode you’re in.
I’d love to see a universal kill switch, with protection against triggering in flight. Of course, you may WANT to trigger it during flight in flight in case of emergency, so drawing the line for that will be tough.
I have a kill switch on my automated zero turn mower. I don’t think you are looking for this drastic a kill action, but for what it’s worth I will describe it.
The RC receiver is connected to the Pixhawk via SBUS, but the individual PWM outputs function also. So I connect output 5, which I have activated by the Channel 5 switch on the transmitter, to an Arduino which will open a relay that kills the engine when I flip the switch. In addition, the RC receiver will hold previous value on the PWM outputs if it loses communication with the transmitter, except for Channel 3 (normally throttle) which will drop below minimum. I connect channel 3 to the Arduino also, and have it watch for the low PWM. So, if the mower gets out of range of the RC transmitter, the engine is killed also.
What I like about this is that the kill function via the channel 5 switch is totally independent of the Pixhawk. My rover could really hurt someone if things got out of hand.
“in flight” is always a heuristic. We do not use it for safety stuff.