M2E - Tilting forward under takeoff

[BobbyXo]

Hi!

Have an M2E Dual.

While starting the drone, and starting to takeoff, the drone tilts forward and crash.
Try to hold it in my hand while starting up, and it tilts about 30-40 degrees forward before having the same speed on all motors (listened, so approx)
Tried changing all the blades, checking the motors, they feel the same, checked direction of motors and blades, ok.
Calibrated RC, Compass, IMU (several times) Result is the same.
Any suggestions? Have downloaded a .dat file if interested.

Br Bobby.

 

[Phantomrain.org]

Are you using the Auto Take off or are you lifting it up on your own to slowly ?

 

[BobbyXo]

Tried both, same result

 

[BobbyXo]

Have had hundred of flights with it, first time i have experienced this problem

 

[Phantomrain.org]

Seems you have no choice but to isolate each Prop now.

Phantomrain.org
Gear to fly your Mavic 2E in the Rain land Land on the Water.

 

[sar104]

Post the DAT file.

 

[sar104]

Take a look here. M2E Log files - Crash

Those are aircraft DAT files, not mobile device DAT files which are what is needed. Aircraft DAT files for the Mavic 2 are only readable by DJI.

 

[BobbyXo]

I Think this can be used then

 

[slup]

I Think this can be used then

Mmm ... doesn't seem to be a simple case of swooped props, it's something else.

The AC pitch forward ... & that is consistent with how the motors behave & how they are commanded. The rear motors rev definitely up much more than the front's ... & the command percentage tells the same story, the rear's is commanded much more than the front's. And it's equal with the current draw.

If the motors are commanded like this & the props are on in a correct way the AC shall flip forward.

Do you hold the AC in your hand... according to the DAT the AC have an unusually large back tilt of 20 degrees before the take-off?

Haven't seen a case like this before @sar104 ... ESC problems?

 

[Rabber]

Hi!

Have an M2E Dual.

While starting the drone, and starting to takeoff, the drone tilts forward and crash.
Try to hold it in my hand while starting up, and it tilts about 30-40 degrees forward before having the same speed on all motors (listened, so approx)
Tried changing all the blades, checking the motors, they feel the same, checked direction of motors and blades, ok.
Calibrated RC, Compass, IMU (several times) Result is the same.
Any suggestions? Have downloaded a .dat file if interested.

Br Bobby.

If it is tilting forward, the front is either not generating enough thrust or the rear is generating too much

 

[GFields]

Interesting, Following. Thanks for sharing!

 

[BobbyXo]

If it is tilting forward, the front is either not generating enough thrust or the rear is generating too much

Yes, but why?

 

[360 Guy]

What happens at take off when you have the forward stick held back a tad?
You could have a sticky forward stick.

 

[slup]

What happens at take off when you have the forward stick held back a tad?
You could have a sticky forward stick.

If you look at the log it's pretty clear that this have nothing to do with any stick inputs ... the blue graph is the pitch stick & it's not touched but the AC pitch heavily forward (red graph) immediately after the take-off.

(click on all charts below to make them larger)


Comparing the motor rpm's vs. how they are commanded by the FC in percent show that something make the rear motors spin nearly twice as fast than the fronts ... & the amount of command agrees with that, the fronts are much less commanded than the rears.

Here the rear motors with the rpm's & command percentage ...



And here the fronts ... (look at the chart legend below the chart for comparison, the chart axis is different scaled)



So ... if this would have been a simple case of mixed props on the fronts & therefore not creating any thrust, the front motors had been commanded to 100% by the FC resulting in max rpm's as the AC pitches forward uncommanded. But this isn't the case, the rpm's is consistent with how the FC commands them. Something else is going on ...

 

[sar104]

If you look at the log it's pretty clear that this have nothing to do with any stick inputs ... the blue graph is the pitch stick & it's not touched but the AC pitch heavily forward (red graph) immediately after the take-off.

....Something else is going on ...

I think it has everything to do with stick input, assuming this was a manual takeoff, which it appears to be. Look at the stick inputs - in particular the throttle and the resulting motor speeds:



After the initial CSC to start the motors, at 3.6 seconds that's not remotely enough throttle to take off; all the motors are too slow, and gentle throttle inputs while on the ground will always lead to tipping over. Which it promptly did, flipping over forwards:



For comparison, here are the equivalent data for a manual takeoff of my M2EA, with full throttle applied, as required:

 

[slup]

I think it has everything to do with stick input...

Mmm ... not convinced.

2 reasons mainly ... according to the OP this happens both in auto & manual take-off. Then it appears that that minimal blip on the throttle (0,09=10%) is ended when the pitch start to move, can really such a short small blip lasting only for half a second flip it from a +20 degree pitch all over?

 

[sar104]

Mmm ... not convinced.

2 reasons mainly ... according to the OP this happens both in auto & manual take-off. Then it appears that that minimal blip on the throttle (0,09=10%) is ended when the pitch start to move, can really such a short small blip lasting only for half a second flip it from a +20 degree pitch all over?

Yes - if the aircraft state flag has transitioned from ground to air, which it did. I missed the comment regarding having tried auto takeoff due to an "ignore" setting. The DAT file in question shows assisted takeoff, which is a regular takeoff, not an auto takeoff.

 

[Cagey]

This could be an IMU issue.
I would suggest trying a recalibration?

 

[sar104]

This could be an IMU issue.
I would suggest trying a recalibration?

The IMUs appear to be fine - see the pitch/roll data above.

 

[slup]

@sar104 ... any ideas too what it can be, seen anything similar before, can the ESC's cause this?

Also... +20 degrees pitch at take-off, is that the normal position standing flat for a M2... my MA1 only stand at +7. Can a placement in a up-slope for take-off cause the rears rev up to much making it flip forward?... Or isn't the +20 degrees true & something is actually wrong with the IMU calibration there?