NTSB Identification: DEN00GA022.
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Accident occurred Wednesday, November 24, 1999 in RIFLE, CO
Probable Cause Approval Date: 01/02/2002
Aircraft: Bell 206 L-3, registration: N617DE
Injuries: 1 Uninjured.

: NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this public aircraft accident report.

While on a cross-country positioning flight in cruise flight, the helicopter's engine lost partial power, and the pilot conducted an autorotation to a field, which was rough and uneven. During the landing sequence, the lower wire cutter dug into the uneven ground, the helicopter rocked forward and the skid support cross tubes buckled aft. As the helicopter settled, a main rotor blade struck the left winglet of the horizontal stabilizer, and the tail boom was wrinkled. Examination of the engine revealed that the angular contact ball bearing on the power takeoff shaft had failed. The balls from the bearing had fallen into the gearbox oil sump, and a ball had lodged in the oil exit port, blocking the flow of oil out of the gearbox. The gearbox filled with oil, the oil tank emptied, and power section components began to overheat due to lubricating oil starvation. Engine records provided evidence that during maintenance performed 28.7 hours prior to the engine failure, repair station personnel had removed, inspected and reinstalled the failed bearing. Examination of the bearing provided evidence that it had been pressed apart and reassembled with the outer race reversed. The manufacturer authorizes no disassembly of the bearing. According to the manufacturer, with the outer race reversed, the bearing will immediately start to deteriorate when placed in service.

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

a forced landing on rough, unsuitable terrain. A contributing factor was the partial loss of engine power, which resulted from improper maintenance by repair station personnel.

Full narrative available

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