Accident Summary
A helicopter operated by a student pilot and a certified flight instructor (CFI) was involved in a crash after experiencing a binding collective issue. The aircraft had been released by maintenance just prior to the flight after troubleshooting a squawk concerning a 'binding collective.' The flight was local, lasting about an hour, during which the crew practiced precision hovering and rapid decelerations.
Flight Details
During the rapid deceleration maneuvers, the aircrew felt a binding condition in the collective and noted it to inform the maintenance section. After the last rapid deceleration, the helicopter climbed to an altitude of 1,500 feet above mean sea level (MSL). While rolling level from a turn at a speed of 45 to 50 miles per hour (mph), the aircraft began to shake violently, and a loud 'bank' sound was heard. The helicopter then started a descent as if the collective had been slammed to the bottom.
Accident Sequence
With the collective fully raised and the engine and rotor RPM (revolutions per minute) above the green arc, the helicopter continued to descend as if it were in a full autorotation. The crew used the cyclic and antitorque pedals to avoid power lines, but the main rotor struck a tree, and the helicopter subsequently crashed and burned.
Post-Crash Examination
Examination of the wreckage revealed that only overload failure was found in the collective components. No other failures or anomalies were reported.