Err: thrust_loss_check -1 and fall down [solved: bad ESC calibration]

Hello everyone, I hope someone can help me, replace the obsolete dji controller with a CUAV V5 nano, follow the steps suggested in these instructions

But without any success, It is an agricultural hexacopter with 24 inch propellers T-MOTOR P60 340KV Brushless Motor x 6
T-Motor Flame 80A x 6
T-Motor MF2211 Folfing Propeller x 6
And a quad controller pixhawk v5 nano
Battery 12S 22.000 Tattu 25C x 1
Without any weight, it flies perfect, I did an autotune and it did it without any problem, when filling it with 5 liters of water it also worked according to what was programmed, but when filling it with 9 to 10 liters, it only raised about 70 cm from the floor and it turned uncontrollable on himself in yaw i suddenly descending, turning on several occasions.
Excuse my grammar, English is not my native language.

I appreciate all the help you can give me.
Thank you
Log files: 11-48-13.bin (274.4 KB) 2021-01-21 12-23-27.bin (691.5 KB) 2021-01-21 12-33-13.bin (664.2 KB)


I am new to this, but on the face of it you appear to describe a lack of sufficient power to lift the heavier load. The limited climb ability suggests to me an inability to rise out of ground effect.

You haven’t told us what sort of battery you were using. Insufficient current capacity could be the cause of your problem.

Posting a flight log might enable one of the experts here to pinpoint the cause of your problem.

I think that you have the motors tilted, or your ESC are not properly calibrated because whereas motor 2 reaches the maximum, motor 1 is only about 1400us:

And change MOT_THST_EXPO to 0.2 for those ESCs. T-Motor linearize their PWM thrust curve.

Hi Davidae i change MOT_THST_EXPO to 0.8 acording to this graph

Thanks Paul D Yeager

My battery is a 22,000 mAh 12S tattu
Thanks for your answer

T-Motor told me they don’t do this on any of their ESC’s. I’m not suggesting a parameter value just noting how they replied when I asked the question.

That is good to know, I understood that for those ESCs that value had to be changed.

I kept seeing that posted also and then while helping someone with Flame ESC’s they said they couldn’t get an answer about it. I emailed Sales/Tech support and they replied right away saying they don’t have that function and that it is typically done on the Flight Controller.

This makes sense to me because they don’t know what motor/prop combination will be used with them unless they are supplied as a Combo-pack which of course they offer.

What is the estimated take-off-weight w/o a payload?

take-off-weight without payload 15 kilos or 33 pounds
take-off-weight with payload 20 kilos or 44 pounds

10L of water weighs 10kg but in any case that craft should fly at 30kg TOW. You say 24" props and MF2211 props, which is it?

And just to be sure 12S right?

Sorry, they really are 24 "not MF2211 props and 12S 22,000 mAh 25C battery

You should have plenty of thrust for take-off I think. No current data available?

All motors in the right order and direction when running Mission Planners Motor test (props off)? Be sure you understand the order the Test is run!

Hi Dave, the engines are in the correct order, in fact with 5 liters, I fly perfect, do the missions and apply the product in flight, but I have never been able to apply more than 7 liters

Yes, now that you mention it, it makes a lot of sense.

Can you test the rpm of each motor under heavy load? Maybe there is an electric problem with some ESC or motor. For example a bad solder point increases the resistance and makes the voltage drops under heavy current events, like when you try to lift more kg.

Can you post a log from a successful flight with 7L?We need to look at a flight off the ground with some load. It would really help if you had current logging.

Unfortunately I do not have them, delete everything when I start to have problems with weight so as not to be confused

I think you will have to make another successful flight with a known load.

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I don’t think 340 kV, 24 inch and 12S is the right combo. For 12S one needs the 170 kV P60.

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Hello everyone, thanks to those who collaborated in the solution.
I tell you that the problem was the calibration of the ESCs. The maximum pulse was 1760 and I managed to upload it to 1986 and it works perfectly.

Thank you all