Back engines seems weaker than the front. Won´t Take off.

[Tornestam]

I am new to the forum and to drone flying and just went back from Bali (32 degrees) had som fun with the MM it flew pretty good. Had a notice that engines were maxed but thought they were over heated flying for almost 20 min in the sunset. Came back to Stockholm, Sweden with 0-2 degrees. I took it out and did all IMU and Compass calibrations and it worked good. Got som messages about a zone in the city and about 10k from the airport. Put flight level to 30m...When I was starting and trying to do the app-assisted take off it seems like the front engines were overpowering the rear. Result was a tilt and rear propellers touched the ground and MM shut down. I tried again but the issue w back engines working too weak and resulting in NO Take off. Anyone hade the same?

 

[new2mavic]

If you can share the .TXT and .DAT flight log files here, may be the reasons can be identified. Follow this thread to get the files : Flight log retrieval and analysis guide

 

[Meta4]

I tried again but the issue w back engines working too weak and resulting in NO Take off.

It's extremely unlikely that your rear motors are too weak.
If you launch yourself and give the drone a good kick into the air, how does that work?

 

[Tornestam]

new2mavic,
I retrieved them through iTunes. Hey! Thanks. I attach the files for the 2 attempts I did yesterday. It looks like the Matrix to me. I can not really read them and get something out of it but someone might. Thanks for engaging and caring.

 

[Tornestam]

It's extremely unlikely that your rear motors are too weak.
If you launch yourself and give the drone a good kick into the air, how does that work?

I was actually thinking in that direction for a while but chickened out in case of the MM just go straight into the concrete and break. I am a cautious old man that rather try the smooth way first and then maybe go violent when nothing else work.

 

[Meta4]

I was actually thinking in that direction for a while but chickened out in case of the MM just go straight into the concrete and break. I am a cautious old man that rather try the smooth way first and then maybe go violent when nothing else work.

No .. don't try to launch slowly and gently.
Get that drone up a metre or two very quickly and then pause.

 

[Tornestam]

No .. don't try to launch slowly and gently.
Get that drone up a metre or two very quickly and then pause.

I´ll try this afternoon, after work. You mean start and take off with manually and not physically throw it up in the air, right.

 

[Meta4]

I´ll try this afternoon, after work. You mean start and take off with manually and not physically throw it up in the air, right.

That's right.
Push the left stick full forward and get the drone away from the ground as quickly as you can.

 

[Tornestam]

That's right.
Push the left stick full forward and get the drone away from the ground as quickly as you can.

So I could not really wait. went back during lunch and tried again. First with auto takeoff and the same result. A little stagger of the front and then slid back and stopped. Then I started manually in P mode and had the same experience. I switched to S mode and tried again. Full forward on the left stick and it took off. First a little wiggly (as if it was a little rusty...) and the stabilised. I got it to hover nice. I switched to P mode and went up and down and flew around just a little. Landed manually. After that short flight my horns grew out and I tried the automate start in P-mode and it worked fine - and landing i automate too. Great. I have to rush to work but I am definitely going to hard test it tomorrow.

Thank you Meta4 for encouraging me to go a little "wild"

 

[Tornestam]

todays .txt and .dat
best
Törna

 

[slup]

The motor revs is pretty normal looking at your first supplied DAT logs ... Higher rear then front as it should.

2 thing's come to my mind ... you did the IMU calibration on a perfect leveled spot? And how about the rear props, do the blades swivel easily on the screws, if not perhaps they didn't spread apart properly when you tried to ease it up in the air?

 

[Starz]

Just a curiosity question for the op. What prompted the imu calibration?

 

[sar104]

Yes - there is something wrong with this aircraft or its props. It can fly but the takeoffs are marginal due to a very large positive pitch excursion that triggers the failed takeoff procedure:



A successful takeoff later had exactly the same problem, but just fell short of triggering the abort:



Have you tried swapping the props?

 

[Tornestam]

Just a curiosity question for the op. What prompted the imu calibration?

well, some of these youtubers saying that the IMU and Compass calibrations is vital and do it rather once too many times than less. I this thread I read the opposite and that actually make sense. I made the latest IMU and Compass with the arms (propellers) folded out like in flight mode...
Some of these youtubers also can not finish a sentence without the word "cinematic"

 

[Tornestam]

Yes - there is something wrong with this aircraft or its props. It can fly but the takeoffs are marginal due to a very large positive pitch excursion that triggers the failed takeoff procedure:

View attachment 93240

A successful takeoff later had exactly the same problem, but just fell short of triggering the abort:

View attachment 93241

Have you tried swapping the props?

No, I have not tried any modification of the vehicle. they look OK I think. I can try swapping the rear for the new ones that I got in the package. making sure I look out for whit or black tips. I will fly it tomorrow and try different flight mode and go manual and auto take offs before I start messing with the screwdriver and changing propellers.

Thank you for graphs and some explanations Sar104

 

[new2mavic]

There is definitely something wrong with the rear motors / prop. When hovering indoor ( ie , no wind ), the speed of the motors of my Mini at the back is around 11k but those of the OP's Mini is over 14k which is the maximum achievable by mine.

My Mini :

 

[Tornestam]

Yes - there is something wrong with this aircraft or its props. It can fly but the takeoffs are marginal due to a very large positive pitch excursion that triggers the failed takeoff procedure:

View attachment 93240

A successful takeoff later had exactly the same problem, but just fell short of triggering the abort:

View attachment 93241

Have you tried swapping the props?

The latter one is probably the manual one? where I went full throttle on the left stick forcing it to rise.
But it also worked with the automatic take off. But Yes I see the graphs and it does not look smooth. How should a correct graph look like? And again thanks for engaging in my matter.
Törna

 

[sar104]

The latter one is probably the manual one? where I went full throttle on the left stick forcing it to rise.
But it also worked with the automatic take off. But Yes I see the graphs and it does not look smooth. How should a correct graph look like? And again thanks for engaging in my matter.
Törna

There should be no sudden pitch excursion on takeoff. And judging by @new2mavic's data, the rear motors should not be spinning that fast in level flight.

 

[sar104]

The latter one is probably the manual one? where I went full throttle on the left stick forcing it to rise.
But it also worked with the automatic take off. But Yes I see the graphs and it does not look smooth. How should a correct graph look like? And again thanks for engaging in my matter.
Törna

Yes - that one was manual:

 

[new2mavic]

I would suggest to swap the props at the front with those at the back and try again. Make sure that thread lockers are applied to the threads of the screws holding the props and that the thread lockers are fully cured before flying.