What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
The subject pilot stated while in cruse flight he heard a loud noise and smelled something unusual, at that point he sensed he was loosing power and attitude he then entered an autorotation. While atempting to make an emergency landing in a grassy field the right hand skid gear inpacted the ground and the aircraft rolled over on its right side and was substantually damaged. The following was noted of the engine to main rotor drive belts.1) - one of the two sets of main rotor v-drive belts were found to be separated and broken in half.2) - the remaining set of main rotor v-drive belts were found to be turned inside out with the vee groove facing outwards, there was a wear pattern on the belts indicating they were running on the pulleys in the insideout direction. Upon inspection of the aircraft maintenance records it was noted the subject aircraft had undergone a 2200 hour inspection 86.6 hours prior to this accident, at that time the drive belts were replaced. The subject airman was asked if he was aware of how long it took from when the main rotor clutch switch was engaged for the main rotor to start turning, he stated on the last flight prior to the autorotation it took at least seventeen (17) seconds or longer he also stated in the flights prior he had noticed it taking substsntually longer than ten (10) seconds for the main rotors to start turning after clutch switch engagement. The Robinson Helicopter pilot's operating handbook states during engine start up the main rotor blades should turn in less than five (5) seconds. The Robinson Helicopter maintenance manual states in a caution and note that a delay of more than five (5) seconds between clutch switch engagement and rotor turning indicates excessive slack in the belts and to preform a belt tension actuator limit screw adjustment to obtain the proper belt tension.
As the FAA filed it
THE SUBJECT PILOT STATED WHILE IN CRUSE FLIGHT HE HEARD A LOUD NOISE AND SMELLED SOMETHING UNUSUAL, AT THAT POINT HE SENSED HE WAS LOOSING POWER AND ATTITUDE HE THEN ENTERED AN AUTOROTATION. WHILE ATEMPTING TO MAKE AN EMERGENCY LANDING IN A GRASSY FIELD THE RIGHT HAND SKID GEAR INPACTED THE GROUND AND THE AIRCRAFT ROLLED OVER ON ITS RIGHT SIDE AND WAS SUBSTANTUALLY DAMAGED.THE FOLLOWING WAS NOTED OF THE ENGINE TO MAIN ROTOR DRIVE BELTS.1) - ONE OF THE TWO SETS OF MAIN ROTOR V-DRIVE BELTS WERE FOUND TO BE SEPARATED AND BROKEN IN HALF.2) - THE REMAINING SET OF MAIN ROTOR V-DRIVE BELTS WERE FOUND TO BE TURNED INSIDE OUT WITH THE VEE GROOVE FACING OUTWARDS, THERE WAS A WEAR PATTERN ON THE BELTS INDICATING THEY WERE RUNNING ON THE PULLEYS IN THE INSIDEOUT DIRECTION.UPON INSPECTION OF THE AIRCRAFT MAINTENANCE RECORDS IT WAS NOTED THE SUBJECT AIRCRAFT HAD UNDERGONE A 2200 HOUR INSPECTION 86.6 HOURS PRIOR TO THIS ACCIDENT, AT THAT TIME THE DRIVE BELTS WERE REPLACED. THE SUBJECT AIRMAN WAS ASKED IF HE WAS AWARE OF HOW LONG IT TOOK FROM WHEN THE MAIN ROTOR CLUTCH SWITCH WAS ENGAGED FOR THE MAIN ROTOR TO START TURNING, HE STATED ON THE LAST FLIGHT PRIOR TO THE AUTOROTATION IT TOOK AT LEAST SEVENTEEN (17) SECONDS OR LONGER HE ALSO STATED IN THE FLIGHTS PRIOR HE HAD NOTICED IT TAKING SUBSTSNTUALLY LONGER THAN TEN (10) SECONDS FOR THE MAIN ROTORS TO START TURNING AFTER CLUTCH SWITCH ENGAGEMENT. THE ROBINSON HELICOPTER PILOT'S OPERATING HANDBOOK STATES DURING ENGINE START UP THE MAIN ROTOR BLADES SHOULD TURN IN LESS THAN FIVE (5) SECONDS. THE ROBINSON HELICOPTER MAINTENANCE MANUAL STATES IN A CAUTION AND NOTE THAT A DELAY OF MORE THAN FIVE (5) SECONDS BETWEEN CLUTCH SWITCH ENGAGEMENT AND ROTOR TURNING INDICATES EXCESSIVE SLACK IN THE BELTS AND TO PREFORM A BELT TENSION ACTUATOR LIMIT SCREW ADJUSTMENT TO OBTAIN THE PROPER BELT TENSION.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.