Plane crash during Auto TakeOff

The direction the plane is facing when you trigger take off mode armed.

Well… its definitely as the Wiki says - when we unsupress the throttle
we lock in that heading - and not before.

Do you think the wiki description needs clarification?

If so, do you have any suggestion?

We could explicitly mention it’s nothing to do with heading-at-power-on
(which FWIU is used by some “just-get-me-home” autopilots). Note that
there are several good reasons for us not to do that - one good one is
that we might not really know our heading if you don’t have a compass (we
then generally require movement to determine our heading).

Painless360 has a detailed video on this . The takeoff bearing is fixed upon GPS lock .
To me that is synonymous with initializing the IMI since they happen together upon startup .

Thanks for the clarification. I noticed this I need to point the plane to the north if not use a compass during startup. If not, the heading degree will not be correct.

Does this suggest set up a takeoff waypoint is better than using takeoff mode? at least the plane knows the takeoff wp is the target direction.

… are you talking ArduPilot there? Link to video if so.

Thanks for the clarification. I noticed this I need to point plane to north if not use compass during start up.

… what difference do you see based on the plane’s initial yaw value?

Does this suggest set up a takeoff waypoint is better than using takeoff mode? at least the plane knows the takeoff wp is the target direction.

There’s less that can go wrong with a takeoff wp - but its far less
convenient than takeoff mode. We do a chunk of work to try to deal with
bad headings in takeoff mode.

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The difference I noticed is before taking off.

The different is the delta between north and the direction the plane point to when power up.

For example, if the plane is pointed to east during powering up, there is 90 degree delta between the plane pointing and real direction when rotating plane before taking off. I think this is due to the initial degree is zero when powering up without a compass.

That’s why I point the plane to north when plug in battery. Not sure if I need to do this or not. I think the arduplane will learn the direction from gps track when moving enough distance.

That’s not right. You need to sort out that compass.

Yes. I solved this by pointing the plane to north when power up. There is no delta if I do this.

I noticed the case in the example if I didn’t point the plane north before.

There is no compass on my wing. I disabled it due to mag interference.

Then I suggest you stop using auto-take off. Or fix the compass. AFAIK Auto-take off needs the compass for the heading at slow speed.

Hi Alister,

This is not true. I have performed a 3 digit number (more than 100) of successful “Auto Take off’s” on different ArduPlane versions from 3.9.4 up to 4.0.6 without the need of a compass.

Normally the EKF performs a Yaw alignment after achieving sufficient speed (greather than 5m/s AFAIK).

The usual messages of a typical “Auto Take Off” are shown below.
The status message of the EKF yaw alignment is shown bold.

2020-10-17 17:43:49 ArduPlane V4.0.5 (0bfa2638)
2020-10-17 17:43:49 ChibiOS: d4fce84e
2020-10-17 17:43:49 omnibusf4pro 00330042 3137470B 30363730
2020-10-17 17:43:49 Param space used: 1920/9728
2020-10-17 17:43:49 RC Protocol: SBUS
2020-10-17 17:43:49 New mission
2020-10-17 17:43:49 New rally
2020-10-17 17:43:49 GPS 1: detected as u-blox at 115200 baud
2020-10-17 17:43:49 u-blox 1 HW: 00080000 SW: ROM CORE 3.01 (107888)
2020-10-17 17:44:01 Mission: 1 Takeoff
2020-10-17 17:44:01 Resetting previous waypoint
2020-10-17 17:44:04 Armed AUTO, xaccel = 5.9 m/s/s, waiting 0.0 sec
2020-10-17 17:44:04 Triggered AUTO. GPS speed = 0.1
2020-10-17 17:44:07 EKF2 IMU0 yaw aligned to GPS velocity
2020-10-17 17:44:07 EKF2 IMU0 is using GPS
2020-10-17 17:44:09 Holding course 18505 at 15.2m/s (-8.8)
2020-10-17 17:44:10 Takeoff level-off starting at 9m
2020-10-17 17:44:11 Takeoff complete at 22.72m

Using a compass (on a conventional plane) can make the ground handling before takeoff a lot easier.


As a married man I’m used to be wrong. :slight_smile:

I see you are using auto-take off as part of a waypoint mission. Have you also been successful using auto-take off mode without a compass?


+1 Same for me.

@mavic How do you calibrate your FC ? With Mission planner or QGroundcontrol ? I found one issue with QGC calibration, it reverse board orientation : it costs me a motor and servo …

I only used mission planner.

I had the exact same problem and here is my solution also:

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Most of the time I use Auto take off as part of a mission in “auto” mode. Back in the days of AP3.9.xx versions the option of AutoTakeOff as flight mode was not available. I kept using the old way. It just works for me.
PS: I like your kind of humor. We all know this situations …

Thanks for confirmation. I would be amazed if I would be only one who achieved this.

After watching the videos of the failed attempts to me it looks like you throw the plane with a lot of spin. This is too much for the flight controller to compensate. Especially at low speeds after a tame launch.
Try to push the plane more straight in to the wind.

Your settings should be good enough, You already achieved a successful flight.

A few more tips which worked for me:

  • Try the first flights (take offs) with more wind. It helps at launch.
  • If it does not work. Remove some equipement to make the plane lighter
  • Try a lighter battery (while maintaining the right CoG)
  • After some successful launches you will be more confident and get a better understanding of the weight the plane can handle
  • last but not least: make a few fast steps against the wind while throwing the plane to increase the launch speed

Hope this helps.


@VRquaeler @kikislater
You guys have me questioning some of my understanding of compasses during take off. (not a bad thing, it’s how we learn) I started another thread to discuss it so I don’t derail this one too much. Thanks!

I finally got stable takeoffs by following these tips and analysis logs. Two more changes helped my launching are

  1. overhead launch works better than side throw for my ar wing pro
  2. raise the nose 5 degrees up when calibrating level. This makes the take off much better.

Thanks again @Allister and all guys.


hello i do not have compass.

Do the plane need to face the same heading when in takeoff mode as the same same when i plug in the battery?