Auto-start of engine upon takeoff, any tricks and tips?

After upgrading to the most recent V3 firmware, I try to adjust the TKOFF parameters for catapult launch, TKOFF_MIN_ACC as well as TKOFF_THR_DELAY.

A few questions about auto-takeoff:

Q1) How do I get a clear indication whether APM is armed and just waiting for TKOFF_MIN_ACC to be exceeded? Before triggering the catapult release, I must be sure that everything is ready.

Q2) Which TKOFF values do you propse for a catapult launch (X5 about 1.5kg on a 2.5m rail)?

Q3) Can I simulate a launch by just pushing the plane forward by hand abruptly but without releasing it? I have no idea what acceleration can be achieved, like this.

Q4) Anything else I must consider when performing auto takeoffs, except inserting a WP1 of type TakeOff?

There is unfortunately no indication that TKOFF is ready, however the MP will report when the plane is throttle armed but just to be sure I normally click Restart Mission and watch the next waypoint number change from 0 to 1 on the HUD which can be used to “confirm” readiness.

For catapult launch I used no delay and 10 m/s/s (which I think is about 1G)

Yes you can give it a pretend throw at that level to see if it starts (or lower it for this test)

You will have full control surface override including throttle so if the throttle doesn’t start so be ready to take over in case it doesn’t start.

If your plane will stay put on the catapult at ArduPlane:THR_MAX or ArduPlane:TKOFF_THR_MAX then you can set TKOFF_THR_MINACC to 0, then the motor will start when you switch to auto confirming mission start and you can release the catapult. I do this with all our hand launches now, count the launcher down, switch to Auto and he knows not to throw until the motor starts.

Question… For auto takeoff using a hand launch with TKOFF_THR_MINACC to 0 are you saying the motor will startup as soon as you go to auto? I am ready to try this but making sure I read and understand everything. Are there any other settings I should be aware of?


Yes it will start straight away.

That’s it I think, just make sure you have a takeoff command as the 1st in your mission, set the altitude of that to 50m or so and your takeoff angle to whatever you’re comfortable with, I use 16-18°. If you’re throwing throw straight at the horizon not too much up, the plane will nose up when it’s flying.