Primary finding
Probable cause
The failure of the aft segment of the tail rotor drive shaft for undertermined reasons. A contibuting factor was the lack of suitable terrain for the foced landing.
Investigator assessment
Analysis narrative
The 2,363-hour pilot reported that he was maneuvering the helicopter at an altitude of 30 to 60 feet AGL, with 5 to 10 knots forward airspeed when the nose of the helicopter started to move to the right. The pilot corrected for this with the left pedal. The nose of the helicopter stopped momentarily then started moving back to the right and could not be stopped with full left pedal. The helicopter was spinning uncontrollably to the right and the engine and rotor RPM increased. The pilot tried to hold the helicopter level with the cyclic, lowered the collective, held full left pedal and started to retard the throttle when contact with the ground occurred. The helicopter came to rest on its left side. The pilot reported that the tail rotor was not turning when the helicopter hit the ground. Examination of the helicopter by the operator revealed that the aft segment of the tail rotor drive shaft, approximately 24 inches forward of the tail rotor gear box attach point, was separated. The reason for the separation was not determined.
Source record
Factual narrative
On October 7, 2003, at approximately 1158 central daylight time, a Hughes OH-6A helicopter, N8524Z, registered to and operated by the U.S. Border Patrol, El Paso, Texas, was substantially damaged during a forced landing following a loss of tail rotor effect near Eagle Pass, Texas. The commercial helicopter pilot, sole occupant of the aircraft, sustained minor injuries. Visual meteorological conditions prevailed and a flight plan was not filed for the public use flight. The local flight originated at 1021 from the Del Rio International Airport, near Del Rio, Texas, and was destined for the Maverick County Memorial International Airport, near Eagle Pass, Texas. According to the Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2), the 2,363-hour pilot reported that he was maneuvering at an altitude of 30 to 60 feet AGL, with 5 to 10 knots forward airspeed when the nose of the helicopter started to move to the right. The pilot corrected for this by applying left pedal. The nose of the helicopter stopped momentarily then started moving back to the right and could not be stopped with full left pedal. The helicopter was spinning uncontrollably to the right and the engine and rotor RPM increased. The pilot tried to hold the helicopter level with the cyclic, lowered the collective, held full left pedal and started to retard the throttle when contact with the ground occurred. The helicopter came to rest on its left side. The pilot reported that the tail rotor was not turning when the helicopter hit the ground. Examination of the helicopter by the operator revealed that the aft segment of the tail rotor drive shaft, approximately 24 inches forward of the tail rotor gear box attach point, was separated. The reason for the separation was not determined.