ATL04TA047 · Bell OH-58A

The flight was dispatched on a routine police call and was circling at 500 feet above ground level when the second pilot felt a reduction in engine power and noted a split in the rotor and turbine tachometers. After the throttle position was checked, the pilot-in-command realized that there was a reduction in engine power as the engine rpm went to idle. The pilot lowered the collective to enter an autorotation descent at 60 knots. The helicopter collided with the ground in a marshy area with a tail low attitude. The engine continued to run at idle power until the crew shut down the engine using the throttle and fuel valve handle. The pilot did not report any mechanical malfunctions with the helicopter prior to the accident. Examination of accident site revealed the wreckage crashed in a densely vegetated and marshy area, three miles east of Ruskin, Florida and 18 miles south of Tampa, Florida. Examination of the aircraft revealed damage to the bottom of the fuselage, one main rotor blade was severed three and a half feet from blade-retaining bolt, both pitch change links fractured, the tail boom severed just forward of the horizontal stabilizers, one tail rotor blade was bent 90-degrees near the root of blade and the lower leading edge of the aft vertical fin was damaged. It was also noted that the engine to transmission drive shaft exhibited a bend of 10-degrees. Examination of the engine revealed no anomalies in the general physical condition and security of the engine as it was mounted in the accident helicopter. King Laboratories in Tampa, Florida tested the fuel samples both from the helicopter and the tank from which the helicopter was refueled. The samples were determined to be in compliance with the standards established for Jet A fuel. The first five attempts to preform a functional test-run of the engine were unsuccessful and the original fuel control was replaced. On the sixth attempt, the engine ran without issue. The power turbine governor and fuel control were bench tested at the Honeywell facility and no pre-existing conditions were identified that would have prevented normal operation in either assembly. An additional engine run with the original controls installed was performed at the Rolls-Royce plant and the engine ran without irregularities and nearly to performance standards for new production engines.

Verbatim NTSB analysis and probable cause from the NTSB dataset