What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
On takeoff engine lost power, aircraft settled to ground and rolled over onto its side. (-4)the pilot of a turbine powered helicopter said he began a hover about three feet above the ground, turned the helicopter into the wind, and initiated a takeoff. According to witnesses, the helicopter had started to move forward and had attained an altitude of about 25 feet, when they heard a change in the sound of the engine. The pilot stated 'as power was brought in, a loud metallic type pop was heard.' He said the helicopter yawed left after the 'pop' was heard, and that it did not respond to control inputs. The helicopter flew over an embankment, and its rotor blades struck the side of the embankment. After the blade strike, the helicopter rolled over onto its left side, then on its right side and came to rest. Examination of the helicopter and its components revealed the attachment bolts that connected the driveshaft to the geared portion of the driveshaft coupling had failed. Metallurgical examination revealed that two of the bolts had failed from fatigue, the other two bolts had evidence of overload failure. Also, after di assembly, a tension (centering) spring was discovered to be missing from the transmission end of the driveshaft (which would have allowed the bolt heads to contact the grease retaining plate). The last annual inspection of the helicopter and engine was on 11/3/93.
As the FAA filed it
ON TAKEOFF ENGINE LOST POWER, AIRCRAFT SETTLED TO GROUND AND ROLLED OVER ONTO ITS SIDE. (-4)THE PILOT OF A TURBINE POWERED HELICOPTER SAID HE BEGAN A HOVER ABOUT THREE FEET ABOVE THE GROUND, TURNED THE HELICOPTER INTO THE WIND, AND INITIATED A TAKEOFF. ACCORDING TO WITNESSES, THE HELICOPTER HAD STARTED TO MOVE FORWARD AND HAD ATTAINED AN ALTITUDE OF ABOUT 25 FEET, WHEN THEY HEARD A CHANGE IN THE SOUND OF THE ENGINE. THE PILOT STATED 'AS POWER WAS BROUGHT IN, A LOUD METALLIC TYPE POP WAS HEARD.' HE SAID THE HELICOPTER YAWED LEFT AFTER THE 'POP' WAS HEARD, AND THAT IT DID NOT RESPOND TO CONTROL INPUTS. THE HELICOPTER FLEW OVER AN EMBANKMENT, AND ITS ROTOR BLADES STRUCK THE SIDE OF THE EMBANKMENT. AFTER THE BLADE STRIKE, THE HELICOPTER ROLLED OVER ONTO ITS LEFT SIDE, THEN ON ITS RIGHT SIDE AND CAME TO REST. EXAMINATION OF THE HELICOPTER AND ITS COMPONENTS REVEALED THE ATTACHMENT BOLTS THAT CONNECTED THE DRIVESHAFT TO THE GEARED PORTION OF THE DRIVESHAFT COUPLING HAD FAILED. METALLURGICAL EXAMINATION REVEALED THAT TWO OF THE BOLTS HAD FAILED FROM FATIGUE, THE OTHER TWO BOLTS HAD EVIDENCE OF OVERLOAD FAILURE. ALSO, AFTER DI ASSEMBLY, A TENSION (CENTERING) SPRING WAS DISCOVERED TO BE MISSING FROM THE TRANSMISSION END OF THE DRIVESHAFT (WHICH WOULD HAVE ALLOWED THE BOLT HEADS TO CONTACT THE GREASE RETAINING PLATE). THE LAST ANNUAL INSPECTION OF THE HELICOPTER AND ENGINE WAS ON 11/3/93.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.