Motor spin slow than others

Hello, all , im working with APM 2.5, in X configuration, when i arm the APM, one motor (motor 4) spin slow than others 3.

When i calibrate the ESC's in automatic mode, all spin with same speed and work fine, but when
 i arm the APM and test, motor 4 speed slower. 

I changed the motor, but this continue...

Some configuration?

Any help?



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  • Hi, I've just figured out I have the same issue here ( GE260 folding frame with mini APM 3.1 controller )

    - Motor#3 ( back left ) spins slower than others at low throttle commands ( approx less than 30% )
    ESC and motors are soldered, so I really can't swap them for testing, used to shorten previous #3 ESC one year ago .. replaced it, everything was fine using FLIP32 controller, issue appeared as soon as using the Mini APM.. thought it was some PID settings misconfiguration at first glance ..

    I did recalibrate the ESC then ( 4 at the same time ), at "slow" takeoffs the quad flips over itselfs in the #3 direction .. with a quick "40% throttle burst" the motor #3 will behave like the others, allowing a regular takeoff, stabilized, everything's fine ..

    Until I want to reduce my altitude, it most of the time results in a destab into #3 avis, then the quad reacts, bring it back, and destab again in quite a "funny" dance which ends only I if i use the pitch / roll command or throttle up a little bit .. everything's fine again

    At some points, it might lead to a crash ( as testing RTL , the AltHold mode, sometimes has baroglitches, resulting to altitude drop, same #3 issue and crashes this way, or at lower battery levels, it never compensates enough the motor #3 glitch and crashes again .. )

    - Here's a basic scheme of my problem :


    Thanks for any help, notes, ideas ;) 

    Cheers :)

    • I too am having this issue with the Mini APM Pro on Motor 3!  All motors spin at the same speed when armed, but motor #3 only starts spinning up at 1/4 throttle..  I moved the PWM wires to another prop connection and it ran fine, but any motor connected to #3 spins slower..  it is most likely a bad APM..  Bought mine off Amazon and left bad feedback for the seller..  I did not opt to return it because I like its size and everything else seemed to work ok so will try it out in a plane where only one prop is needed.  

      I did notice an issue that if I arm it and the props are spinning slowly, it will automatically disarm if I don't try to power them up..  not sure what that is all about.  If I run the throttle up and then back down, it will stay armed.

      I fooled with this thing far too long, got to try something else now..  Going to put my Pixhawk in it to see how it does.

      Tarot 650 Sport

      DJI E800 Propulsion

      Nano-Tech 8000mah 6S battery

      Atto Pilot 180A for battery monitor

      5v BEC powering the APM

      RFD900 Modem

      DragonLink (Copter version)

    • Think I figured it out..  Still a bad APM though..

      When I lift the APM while in stabilize mode and wobble it around, nothing happens..  Though the artificial horizon in MP does move..

      I put in a regular APM 2.6 and when moved around all the motors go nuts adjusting RPM's while in stabilize mode..  Odd that the artificial horizon is getting input from the gyro but not the motors..  I checked, rechecked and triple checked to make sure I was in stab mode.  

    • Solved the issue of the one motor not spinning up as fast..  I tried EVERYTHING, just about every firmware old, new and beta I could find with no luck..   I installed a regular APM 2.6 on my frame and everything worked fine.. ARGH!  

      Then I save it's parameter file and wrote it to the Mini APM Pro..  it fires up and all motors spin as they should, a lot smoother even! and plenty of power..  They max out at a lot faster RPM now..  Maybe this will help someone else..  Wonder why this happened?  Wouldn't a new firmware install replace all the parameters?

      I'm attaching my file n case you want to try it..

    • Hi, except PID tuning and radio's trimming here are the main differences with mine :
      ( did this with np++ excelent compare plugin .. )

      BAROGLTCH_DIST    250  500  ( yeah I do have some baroglitch appearing, and hate having them in auto / rtl mode -> this causes altitude loss and further unstabilities )
      ARMING_CHECK      1      0     ( arf )

      DCM_CHECK_THRESH    5=>0.8
      EKF_CHECK_THRESH     0=>0.8   ( put it to 0 because this caused me auto-mission to land in the trees once waypoint one reached )

      THR_ALT_P                     0.4 => 1 ( had huge stability issues when loosing altitude, some flips etc .. leaded to previous crashes )
      MOT_SPIN_ARMED         0=>70
      POSCON_THR_HOVER    461=>513

    • Did you have any luck figuring this out? I've had a similar issue... my faulty position will actually cut out completely if I lower the throttle too quickly.

    • its seems new diy builder having the same problem, hehe, i face it too, and still searching for the solution, omg

    • @Christian, just moved on to page 2. Do you have a flight log file? I think some of our developers can help you out. Also, have you tried getting new firmware? Hope you get the guy flying soon!

  • HELLO i checked in status and channel 4 output is lower than other channels.

    I tested in low and high speed, Please see the attached images.

    Can you help me to correct this please?




  • I changed all ESC's to CX-ESC-40A , and the problem persist, motor 4 spin slow

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