20010725023509A

(-23) On July 25, 2001, at approximately 1820 hours (local), Jacksonville sheriff's helicopter N313JP, piloted by hector jose rivera, was asked to perfrom an aerial reconnaissance of a lake in argyle forest; a housing subdivision located in the west/southwest part of Jacksonville. The request was to determine if an automobile might be submerged in the lake. Mr. Rivera, and his designated observer, Mr. John byron colgrove, arrived at the area around 1840 hours and began a visual reconnaissance of the lake. They initially make a high reconnaissance of the lake (500 feet AGL) and then circled back to make a low reconnaissance (150-300 feet AGL). The flight path over the lake was to the east with the wind being out of the east at about 6-12 knots. After the second (final) pass Mr. Rivera made a left turn to the north/northwest followed by a right pedal turn. According to the observer the aircraft started slowing down and the pilot had to increase power to maintain altitude. The aircraft then started making uncontrolled right turns (estimated to be between 8-12 turns) and the helicopter continued to descend with a high engine power/low rotor RPM contacting the roofs of two houses and crashing between them. (.4) on July 25, 2001, about 1840 eastern daylight time, a Bell 206B-III helicopter, N313JP, registered to, and operated by the Jacksonville sheriff's office, as a title 14 CFR part 91 public-use flight, crashed in a residential area in Jacksonville, Florida. Visual meteorological conditions prevailed, and no flight plan was filed. The pilot and copilot received minor injuries, and the helicopter was destroyed. The flight had originated from craig municipal airport, Jacksonville, Florida, the same day, about 1705. The pilot stated that he departed from craig airport on a routine law enforcement patrol, and responded to a call to look for a submerged car in a small lake. The pilot further stated that he started a descent into the area heading east into the wind, and down to 300 feet. He said he made several passes, and on the last pass he made a left turn, and had started turning to the right when the aircraft developed a fast yaw to the right, indicative of imminent loss of tail rotor effectiveness (lte). The pilot said he immediately reduced collective and nosed the aircraft forward, and started losing alti tude altitude fast with no significant improvement in the yaw rate to the right. He said he pulled power to arrest the descent rate, and the yaw rate got faster, and he made a forced landing between two houses, pulling power at the bottom to arrest the descent rate. During the forced landing, the right skid touched down on the side of the roof, the aircraft then rolled left and came down to the ground. The pilot said that prior to the accident, there had been no mechanical failure or malfunction to the aircraft, or to any of its systems. FAA advisory circular 90-95 describes unanticipated right yaw in helicopters, or loss of tail rotor effectiveness (lte) as a critical, low-speed aerodynamic flight characteristic which can result in an uncommanded rapid yaw rate, which does not subside of its own accord, and if not corrected can result in a loss of aircraft control. Ac 90-95 further describes lte as a condition which is not related to a maintenance malfunction, but one which may occur in varying degrees in all single main rotor helicopters at airspeeds less than 30 knots. For further detail on lte please refer to FAA advisory circular 90-95.