Lorida, FL, USA
N91281
Bell UH-1B
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.
On July 16, 2002, about 0930 eastern daylight time, a Bell UH-1B, N91281, registered to Colony Helicopters, Inc., operating as a Title 14 CFR Part 137 aerial application flight, crashed in the vicinity of Lorida, Florida. Visual meteorological conditions prevailed and no flight plan was filed. The aircraft received substantial damage, and the commercial-rated pilot, the sole occupant, received serious injuries. The flight departed a field near the spray grove about 5 minutes before the accident. The pilot stated he was spraying an orange grove and was heading south. He started to make a turn to the west and his airspeed was 22 mph. He was making a spray turn at the end, slow, 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. About 7-12 minutes passed from the time they arrived on the scene to the time the engine was shut down. 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. The ground crewmember reported this to a company mechanic and the mechanic wanted the pilot to call him. Before the pilot could be told to call the mechanic the helicopter had already crashed. A postaccident test run of the engine was attempted at an engine overhaul facility in September 2003. The engine rotated normally and ignition occurred. The engine stopped accelerating after reaching 30 percent speed. Fuel flow was observed to increase during the start attempt to 250 lb/hr and then drop to 125 lb/hr. Three attempts to start the engine were made with the same results. The engine was then removed from the test cell and the fuel control was removed for testing and disassembly inspection. The fuel control was placed on test bench at the engine overhaul facility and a functional test was attempted. The fuel control would produce no more than 90 lb/hr fuel flow regardless of the test position. The fuel control was then removed from the test bench for disassembly examination. Disassembly 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 resulting in the hang starts experienced during the post accident engine test attempts. 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. Maintenance records showed the engine assembly, which included the fuel control, was installed on the helicopter on June 29, 2002, about 40 flight hours before the accident. The helicopter operator had purchased the engine assembly from another company. No records concerning the history of the fuel control were located after the accident.
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.
Source: NTSB Aviation Accident Database
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