Robinson R22
Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Commercial; Flight Crew Rotorcraft
Flight Crew Last 90 Days 250; Flight Crew Total 1900; Flight Crew Type 476
Other / Unknown
Aircraft Equipment Problem Critical
Aircraft Aircraft Damaged; General Flight Cancelled / Delayed
Aircraft
I had just completed all run-up checks and was increasing the throttle to operating RPM.  I heard a thud from behind.  My initial thought was that a drive belt had broken.  When I looked out the door I saw the entire empennage and tail rotor assembly hanging by the rear position light wire.  After inspection the tail rotor gear box mounting bracket had broken in half and the aluminum of the tail cone had ripped and completely separated.  The tail rotor blades struck the bottom of the vertical fin and separated from the aircraft.  No one was injured.  The aircraft owner was notified and came to pick the helicopter up with a trailer.
R22 helicopter pilot reported empennage and tail rotor assembly separated from aircraft.