With the advancement of firmware, (2.9.1), is it OK if I don't launch / arm from a horizontal attitude?

I use a DJI F450 frame, so the APM2 sits on the top plate, and my 4S 4000mAh lipo pack has to be strapped to the bottom, resulting in the quad actually resting on the lipo pack rather than the 4 legs. And I might be adding a GoPro on the bottom which will make things worse. And I often fly from a lumpy grass field.

I would prefer not to have to make the legs taller, if I don't have to.

So question is, is it OK to arm and launch from a tilted position? Say less than 30 degrees.

Oh, and an unrelated question, about RTL in 2.9.1.

Suppose I go the field without a laptop.

Am I correct that if I should wait for GPS fix (steady blue LED on the onboard GPS of APM2), then arm the APM2.  Then the GPS position is stored as the position that RTL will seek to? And everytime I re-arm, the current position is stored as the RTL position?

I ask because I got a bit confused in Flight Planner way point planning page, where there are possibilities to set a certain point as HOME... Does this get overwritten during arming?

Thank you very much!

f450-apm2-20130512.jpg

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  • Developer

    Hi RedPalm, It is not a problem to arm tilted because the only things calibrated during arming are the gyro. Because they are gyro devices, they are calibrated for angular speed, not angular position.

    Accelerometers are calibrated one time through the accelerometer calibration procedure according to the wiki. That calibration is fix. Then it is not influenced by a tilted take off.

    But... If you are using a Rate I amount in your PID rate pitch and rate roll parameters (it is the case for default parameters), then you'll need to take off fastly (throttle should be rised fastly). If not I term will accumulate on the ground and you could end up with a pitched or rolled take off and the associated eventual take off crash.

    Home is stored in the APM each time you re-arm if there is a GPS 3D Lock. If no 3D lock, then home is stored as soon as 3D lock is acquiered.

    So you need to wait for GPS 3D lock to get Home and launch points identicals. Be warned that on the ground, GPS position can be wrong if you have a bad satellite reception specially with building around (multipathing).

    Mission Planner use it only for HIL simulation and to show the resulting heading between Home and the first waypoint.

    Olivier

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