I have not ha a fan break off during battle, and even when Wanna Chopper made its high powered leap into the rafters, so i believe they could sustain alot of knocks. What did fail in that launch - wish i had a G force meter fitted, was the brass lever that hols the carbon brush onto the stator? had snapped. so fan i think is fine.
I may put a call out asking for broken gearboxes from drills as im working on some things atm that could use these.