NTSB Identification: LAX02LA121.
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Accident occurred Monday, April 01, 2002 in Chandler, AZ
Probable Cause Approval Date: 02/05/2004
Aircraft: Rotorway Exec 165F, registration: N21901
Injuries: 1 Serious,1 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The helicopter collided with the ground following a loss of tail rotor drive during a steep approach. After performing various maneuvers, the certified flight instructor (CFI) and the student began traffic patterns to a landing zone (LZ). On short final, approximately 40 feet agl, and 40 mph, the helicopter yawed left slowly. When the helicopter had reached a 45-degree left yaw, the CFI took the controls. As the helicopter approached a 90-degree left yaw, the CFI had applied full right pedal. Simultaneously, he lowered the collective and reduced power. The helicopter rotated 360 degrees about 3 times before impact. Post accident inspection revealed incorrect installation of the forward end of the intermediate drive belt on the intermediate pulley group. The tail rotor drive system uses three belts, interconnected via pulleys at various points within the tail boom, to drive the tail rotor. The forward and aft belts and pulleys were normal. The intermediate belt was found shredded, burned, and separated. The aft end of the intermediate belt was positioned correctly on the rear pulley; however, the forward end was around the wrong pulley, the one meant for the forward belt, which induced a large misalignment of the intermediate belt and consequent rub between it and the pulley side. All pulleys were installed with specified tightness and with fore/aft play as stated in the maintenance manual. Maintenance records for the helicopter indicated that the belts were replaced twice in the past 8 months, both times by the manufacturer. The first time was in August 2001, for a heavy maintenance rebuild. The second time was in November 2001 following a tail rotor strike. The belts had about 200 hours operating time since their last replacement in November.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The tail rotor drive system failure as a result of incorrect installation procedures by the manufacturer's personnel.

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