{"id":37194,"date":"2020-07-13T16:58:20","date_gmt":"2020-07-13T16:58:20","guid":{"rendered":"https:\/\/freeflysystems.com\/?post_type=kb_article&p=37194"},"modified":"2020-07-13T16:58:20","modified_gmt":"2020-07-13T16:58:20","slug":"sb003-alta-x-motor-stall-on-fast-vertical-descent-7-10-20","status":"publish","type":"kb_article","link":"https:\/\/freeflysystems.com\/knowledge-base\/sb003-alta-x-motor-stall-on-fast-vertical-descent-7-10-20","title":{"rendered":"SB003 Alta X \u2013 Motor Stall on Fast Vertical Descent (7\/10\/20)"},"content":{"rendered":"

Date Released:<\/strong> July 10th 2020<\/p>\n

Subject:<\/strong> Alta X Motor Stall on Fast Vertical Descents<\/p>\n

Effectivity:<\/strong> All Alta X<\/p>\n

Require Action:<\/strong> Modify flight envelope (reduce vertical velocities)<\/p>\n

INTRODUCTION<\/strong><\/p>\n

This service bulletin is being issued to alert all Alta X pilots of an in-flight failure that a Freefly test pilot experienced on July 9th 2020.<\/p>\n

BACKGROUND<\/strong><\/p>\n

During flight testing a Freefly test pilot executed an aggressive maneuver in manual mode that involved climbing to ~400ft while initiating a zero throttle zero horizontal speed descent.\u00a0 The pilot let the Alta X fall at zero commanded throttle for 4 seconds.\u00a0 At the end of the 4 second fall the Alta X was traveling vertically at\u00a0 ~ 16m\/s (35mph).\u00a0 At this point Motor 1 (front right) stalled and shut down and the Alta X crashed.\u00a0 The Alta X was equipped with a 20lb payload for this test.<\/p>\n

Freefly replicated the issue by testing on our ground test setup (truck with Alta X motor and prop mounted) and was able to replicate the issue at speeds of 20m\/s to 22.5 m\/s (45 to 50mph)<\/p>\n

Video from the ground test<\/a><\/p>\n

DISCUSSION<\/strong><\/p>\n

Some key points to convey regarding this issue:<\/p>\n