This week I tested and mastered the auto takeoff feature on the APM I've installed on my Nova. It took a few tries and a cracked fuselage to get it, but once I got it performed very well; I set the flight mode to auto, I run down the field, and the motor kicks on without me telling it to, I throw it, and it takes off on it's own. Very cool. 

Seems to be working well, am I doing it right?

Next week I'll be testing the auto land feature, which will be just as exciting. 

Equipment Used:
Airplane: Scratch-built Nova, see for plans and build instructions
Main Camera: iPhone 4s
Airplane Camera: FlyCamOne2

Weight: 32 oz
Thrust: 21 oz
Wing Area: 3.33 square feet
Wing Loading: 5.3 oz per sq ft

If you're interested in building the Nova, I've got free build instructions and plans on my website:


Views: 2533

Comment by Martin witt on February 25, 2012 at 9:32am

i think speed is the key if you run down the field it kicks in but if you stand still it wont

and from what i saw from a static pos. throwing it it gained speed and it kicked in again.


greetz marty


Comment by Gary Mortimer on February 25, 2012 at 10:14am

Your close to being able to enter this T3 round.......

Oh and close that canopy, you will be making an awful lot of drag and weirdness for the AP to handle. Oh and another thing, I think your wing bands really need to be either side, yes a touch more drag but looks to me like your wings might pull apart. 

At the moment there is plainly no weight there, but once you add it details matter.

Your airframe looks great though well done!

Oh and another Oh I don't see any control checks before you launch, always do that something might have come disconnected as you walked out after the last landing. The first time you chuck a plane in auto and it has you will know.... I sometimes think manual take offs are better as it allows you to get the feel that everything is alright and climb to an altitude that you can recover from before committing to auto. Anyhow I digress!

After all that ranting excellent job, your well on your way to crossing America.

Comment by Trent at MyGeekShow on February 25, 2012 at 10:29am

Martin: Agreed, it looks like thats the case, the GPS needs to recognize that it's "taking off". Cool!


Gary: T3! That's true, getting close! About the canopy, I would, but that would cover the GPS and I'm having a hard time moving the GPS to a better location to allow the canopy to close. I'd mount it the side but that would prevent it to see the sky on a bank... Tell me a bit more about the wing bands, I'm not sure I follow you yet...


Thank you!

Comment by Dusan on February 25, 2012 at 10:41am
Once the plane is moving faster than a few m/s (I think 3m/s) it will lock onto a heading engage throttle and hold that heading-throttle until the desired altitude is reached.

Comment by Ryan Beall on February 25, 2012 at 11:02am

I'm pretty sure that it is based on acceleration.  So the trigger is looking for an acceleration above 1.8 G's or so and then it looks for it to come back down below something like 1.2G's then waits like 0.5 seconds.  So the motor will not initialize until after the plane leaves your hand unless your trick it by jerking it forward and waiting for the motor to come one.  You might try changing the delay from when the motor comes on.  I set mine at like 1/2 second and that is just too long for most planes.  I'm not sure if you can set this from the Planner or not but that would seriously help your situation.  However, that acceleration logic is a failsafe to keep the motor from getting your hand so just always keep in mind what triggers the throttle so incase you drop it on the bench or something you don't accidently go to try and catch a prop that is miliseconds from turning your hand into groundbeef.

I'll see if I can investigate this a little more to shed some light on how you can tune it a little better for your situation.



Comment by Ryan Beall on February 25, 2012 at 11:22am

I was wrong about the trigger for auto takeoff.  I couldn't really see where the throttle trigger was though.  You can see from the code below that they are triggering the heading hold based on when the gps sees that the ground speed is greater than 3m/s.  As for the throttle not sure? Have to ask doug probably.

static bool verify_takeoff()
        if (g_gps->ground_speed > 300){
                if (hold_course == -1) {
                        // save our current course to take off
                        if(g.compass_enabled) {
                                hold_course = dcm.yaw_sensor;
                        } else {
                                hold_course = g_gps->ground_course;

Comment by Michael Oborne on February 25, 2012 at 6:41pm

this is the code here

                       if (
                                        (control_mode == CIRCLE || control_mode >= FLY_BY_WIRE_B) &&
                                        (abs(home.alt - current_loc.alt) /span> 1000) &&
                                        ((g.airspeed_enabled ? airspeed : g_gps->ground_speed) /span> 500 ) &&
                                        !(control_mode==AUTO && takeoff_complete == false)
                                ) {
                                g.channel_throttle.servo_out = 0;
Comment by Rigel on February 26, 2012 at 12:23am

Hmmm...strange results.  My motor always kicks in as soon as I switch to Auto for an Auto Takeoff.  I've never had to run like that, which is a good thing because this would entail running off of a cliff for me.

Trent, which version of ArduPlane are you flying?

Comment by Andrew Tridgell on February 26, 2012 at 5:18am

Hi Trent,

The key is the code Michael pasted. The code is meant to be a safety precaution against auto-takeoff when you first turn on. It will not enable the throttle till you get the speed up to 5 m/s. Users often use RTL as the failsafe mode for the receiver - imagine if you switched off the receiver while the plane was on the ground and it entered failsafe and tried to takeoff! This safety feature prevents that.

Comment by Rigel on February 27, 2012 at 2:22am

@Andrew:  When was this implemented?  Also, how do you explain the motor starting on Trent's first launch?


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