crwdns2934241:0crwdne2934241:0 David

crwdns2934249:0crwdne2934249:0:

The shaft could've broken, making it spin freely.

If turning the upper blade still turns the ring-gear in the middle of the copter you need to check if the gearteeth is meshing with its corresponding motor

my 2 cents, hope it helps :)

crwdns2915684:0crwdne2915684:0:

open