I am experiencing a recurring “Potential Thrust Loss” issue on my ArduPilot quadcopter. After about 40–45 minutes of flight, the warning appears, but the affected motor is random (Motor 2, 3, or 4)
When battery voltage gets lower the commanded RPM must increase to compensate it, when it reaches a state that motors need to be commanded full thrust but it still not enough to maintain attitude and altitude you get thrust loss. So this craft is too heavy for this motors / props / battery combination.
Also there are few other problems:
There is yaw compensation - check your props are all in level, ever 2-3 degrees of rotation matters.
It’s overfiltered, with LPF too low and too much FLTT / FLTD
The dynamic throttle notch are not configured correctly, try like this
Indeed it is unpowered/overweight (what kV motors and props?). All you need to see is this section of the log with Motor 4 output maxed out in this event.
Also, the drone frame and weight distribution are well balanced, and the center of gravity has been checked.
I have attached a photo of the motor installation to show how the motors are mounted on the frame. Could you please check if the motor installation and orientation look correct?
Based on these hardware specifications and the attached log, could you please help confirm the most likely root cause? Is it related to insufficient thrust margin, battery voltage sag, filtering/configuration, or another hardware issue? I would really appreciate your guidance so I can identify the exact cause.
Based on these specifications and the log analysis, what changes would you recommend to resolve this issue? Should I change the motor, ESC, propeller, battery, filter settings, or any ArduPilot parameters? I would appreciate your recommendation on the best solution to eliminate this “Potential Thrust Loss” issue.
Looking at motors specs I would say Your issue is related to ESC calibration and/or use dshot. Motor spec with Your props should give You about 7.6kg of thrust at 50% output, which is on the very edge of getting underpowered in theory, but practically it is pass that edge due to lack of any safety margin in that area.
Not sure if output maxed out mentioned above by @dkemxr is caused by thrust loss, where AP will try to increase output of motors unsuccesfuly, or just manevours and not enough of power for the weight. Both cases are no good anyway.
If this ESC supports any type of telemetry I would use it to check motors RPMs and ESC temperatures. And… calibrate ESC, if possible switch to dshot.
Take 700g out of the craft. You have 3kg worth in battery? Sacrifice some flight time and take it out of that if you can’t change anything else. Or, a total rebuild for 12S power perhaps.
I applied the recommended notch filter parameters, and the vibration levels have improved during a short test flight. I haven’t performed a 40–45+ minute flight yet, where the Potential Thrust Loss issue usually occurs. Before I do the long-duration test, is there anything else you recommend checking or changing? Beacuse motor is little heating on changing this parameters..would you recommend something else rather than this??
I would like to share one more update about my setup.
Currently, I am using 2 × 6S 21,000 mAh solid-state batteries, and the total takeoff weight is approximately 7.2 kg.
I am planning to replace them with 2 × 6S5P battery packs built using Molicel P50B cells to provide higher current capability and reduce voltage sag under load.
Do you think this battery upgrade is likely to help resolve the Potential Thrust Loss issue, or do you believe the root cause lies elsewhere?
I am planning to try a different motor and propeller combination to see if it improves the issue.
Current setup:
Motor: Antigravity MN7005-15, 230 KV
Propeller: 24 × 7.2R Carbon Fiber
Planned setup:
Motor: MN6007, 320 KV
Propeller: 22-inch Carbon Fiber
The drone’s AUW is approximately 7.2 kg.
Do you think this new motor and propeller combination is suitable for my setup? Could it help resolve the Potential Thrust Loss issue, or do you think the root cause is elsewhere?
I would appreciate your advice before I proceed with these changes. Thank you.
If you compare both datasheets there should be no problem with 7.2kg AUW (7200/4=1800g per motor), it should hover at near 50% throttle with fully charged battery.
First thing I mentioned was yaw thrust imbalance, you need to get rid of that. 2 motors working at 60% while other 2 at 80% thrust. Please check that all your propellers are perfectly level.
When the battery discharge voltage drops from ~23v to ~19v, 23/19=~1.21, that means that at empty battery the commanded PWM willbe ~21% higher than with fully charged battery.
On the the log 205.bin the motor #4 hovers with ~71% throttle with full battery, while the battery discharge hover throttle for motor #4 increases to 84% (predicted value is 71*1.21=~86%), that’s not enough headroom for attitude control - you have 95% max throttle set. More or less safe headroom value is 20%.
So please check that first, all 4 motors should have same average commanded PWM rate.
