NTSB Identification: MIA02LA133.
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Accident occurred Tuesday, July 16, 2002 in Lorida, FL
Probable Cause Approval Date: 03/30/2004
Aircraft: Bell UH-1B, registration: N91281
Injuries: 1 Serious.
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 pilot stated he was making a spray turn at the south end of a grove and when he started to initiate the turn and pull a little power, he heard a noise, not a real loud boom, just a noise. The helicopter yawed a little bit and lost all lift. It just fell straight down. He didn't have time to look at instruments or anything, it just came straight down like a rock. The ground crew for the spray operation stated they had just refueled the helicopter and put chemical in the tank prior to the pilot departing. A short time later they heard the pilot call on the radio that he had crashed. They went searching and found the helicopter and pilot at the south end of the grove. As they approached the helicopter, the main rotor was still turning and the engine was still running. The pilot was still in the cockpit. They attempted to shut down the engine with the cockpit controls but they were jammed. They then went to the engine compartment and shut the engine off with the fuel control lever. The pilot reported to them that he was attempting to come out of a turn and the engine lost power and the helicopter went down. One of the ground crewmembers reported that the pilot stated during the previous servicing stop that the engine was running hot and losing power. Post accident examination of the engine fuel control showed the pump drive clutch assembly was fractured into two pieces. According to the technician performing the disassembly this resulted in disengagement from the N1 flyweight assembly. The N1 flyweight assembly drives the N1 servo system during normal fuel control operation. The N1 servo assembly determines the amount of fuel supplied to the engine based on the speed at which it is driven. With the N1 servo system effectively disengaged from the fuel control, the system would remain in the start position and the amount of fuel supplied would not be enough to sustain normal engine operation. The technician further stated the pump drive clutch, the mating surface on the flyweight assembly and the bearing located below the drive clutch exhibit excessive wear. The failure of the pump drive clutch can be attributed to this wear. This type of wear occurs over an extended period of operation and is not usually caused by one incident or a sudden impact.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's continued operation with known engine anomalies resulting in loss of engine power due to failure of the engine fuel control pump drive clutch assembly due to wear and collision with the terrain during the resultant descent. Full narrative available
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