SB002 Alta X – Intermittent Motor Start Failure – Update (2/17/20)

Date Released: Feb 17 2020

Effectivity: All Alta X



This service bulletin is being issued to alert all Alta X pilots of an intermittent failure of Motors to start spinning upon initial startup. 


Freefly has received ~5 reports of Motor 1 not starting properly in the field. Freefly has completed the first stage of our investigation into the issues. We developed an automated test that power cycles the Alta X and initiates a startup command.  Over the course of 8,396 test cycles we detected 19 instances in which a motor did not start properly. We have traced the condition back to the Motor Drive and have observed that occasionally the motor drive will falsely signal a ‘phase error’ failure.  We do not understand the conditions for this error to occur and are working to understand the root cause. 


Some key points to convey regarding this issue:

  • We have received no report of motor failure in flight, the failure mode appears to only exist upon startup. Once a motor is spinning there is no evidence that the issue can occur. 
  • We observed various booms (1-4) exhibiting this behaviour.
  • A reboot of the machine has cleared the issue so that normal operation can continue.
  • Throttling up the Alta X without a motor starting can cause a tip over.


  1. Always visually confirm all motors are spinning prior to liftoff
  2. Always perform an attitude control flight check prior to takeoff (demonstrated here)
  3. In case of a motor failure to start, disconnect Alta X flight batteries and reboot machine
    • Please file a ticket with customer support so we can investigate and track this issue

See attached PDF for full details


Still need help? Get in touch with our support team.

Contact Us