MIA05TA124
MIA05TA124

On June 29, 2005, about 1242 eastern daylight time, a Bell OH-58A, N244RP, registered to and operated by St. Johns County Sheriff's Office, made a hard landing following a loss of engine power shortly after takeoff from the St. Johns County Emergency Operations Center (St. Johns EOC), St. Augustine, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the public-use, local flight from the St. Johns EOC. The helicopter was substantially damaged and the commercial-rated pilot sustained minor injury and one observer was not injured. The flight was originating at the time of the accident.

The purpose of the flight was to reposition the helicopter to a nearby high school for a static display. The pilot stated that after starting the engine, he contacted the St. Augustine Airport Air Traffic Control Tower for departure, and after lifting off the ground into a hover, he made a left pedal turn to depart across the southwest parking lot. During climb out while flying between 35 to 40 feet above ground level (agl), and between 30 to 35 knots, he heard a loud "bang" and the helicopter yawed to the right. He later reported that the right yaw could have been him overcorrecting. He lowered the collective and started a left pedal turn in an attempt to land on the grass at the edge of the parking lot. In an effort to clear vehicles below, he pulled collective and continued the turn. He heard the low rotor warning, and observed the low rotor warning and engine out lights were illuminated. He then pulled the rest of the collective to clear the vehicles, and as the helicopter cleared them, it, "...settled rapidly to the ground and impacted the ground behind the cars. The rotor blades struck a car and the top of a truck. One half of a blade departed the aircraft and struck a van in the east parking lot." He performed an emergency shutdown of the engine and he and the passenger were assisted out of the helicopter.

Examination of photographs provided by the St. Johns County Sheriff's Office revealed the helicopter departed from grass located between the front of the St. Johns EOC with a nearby antenna, and a parking lot with numerous vehicles. The helicopter came to rest upright in a northerly direction immediately adjacent to vehicles parked in a parking lot, or an estimated 100 feet from the initial departure point. A car located adjacent to where the helicopter came to rest exhibited extensive damage to the roof and rear portion of the vehicle; a crease was noted on the body of the car. Damage to the top covering the bed of a truck also located adjacent to where the helicopter came to rest was noted. A window of a St. Johns County van parked in the parking lot near where the helicopter came to rest was damaged. Examination of the helicopter revealed the left skid tube was separated but located in close proximity to the helicopter, while the right skid tube was separated only at the aft crosstube. Both main rotor blades were fractured along their length.

The helicopter was removed from the scene and the engine was examined by a representative of the engine manufacturer with FAA oversight. The examination revealed that the drive shaft from the engine to the main transmission was separated at both ends of the KAflex driveshaft. Rotational scoring was noted on the drive shaft, and "oscillatory damage" was noted to the fireshield tunnel between the engine and main transmission. A section of aluminum tubing with attached fittings was noted in the compressor inlet area, and the compressor bell housing was damaged and exhibited "circumferential scoring." A cursory examination of the helicopter by the FAA and engine manufacturer representative revealed no obvious damage to the tail rotor drive system, or tail rotor assembly. The engine compartment did not exhibit evidence of previous oil leaks, and no apparent bending of the engine mounts; the engine appeared aligned with the forward fireshield. The engine was removed from the helicopter and sent to the manufacturers facility for disassembly inspection.

Examination of the engine at the manufacturer's facility with FAA oversight revealed the compressor inlet bellmouth forward of the engine compartment forward fireshield exhibited an inward puncture and rotational scoring. All of the compressor inlet guide vanes were damaged, and the upper and lower compressor case halves had "exit holes with metal bending from outside to inside." All first and second stage compressor blades exhibited leading and trailing edge damage, and all compressor blades of the third, fourth, and fifth stages were fractured near the blade root, while the sixth stage compressor blades were fractured near the tips. The remaining section of blades of the sixth stage compressor were bent opposite the direction of rotation. The compressor impeller exhibited "heavy rub" on all blades, and all vanes of the vane diffuser were damaged. The compressor shroud was noted to be "...heavily damaged from rotational scoring into the base metal" and the compressor air discharge tubes were dented from the inside to the outside. Examination of the accessory gearbox revealed it contained oil and was noted to rotate freely. The oil was golden in color and did not have a burned aroma.

Examination of the combustion section revealed the outer combustion case and combustion liner contained compressor blade and vane material. Examination of the turbine section revealed metal splatter was noted on the first stage nozzle shield and first stage nozzle. All blades of the first stage turbine wheel (gas producer) were damaged near the tips. The second, third, and fourth stage turbine nozzles showed, "moderate deposits of unidentified material on their outer rings." The second stage turbine wheel (gas producer) exhibited metallic deposits and impact marks on all blades. The third and fourth stage turbine wheels (power turbine), exhibited, "...centrifuging of what appeared to be metallic debris to the outer ring." All internal engine shafts were noted to be "intact and unremarkable." All engine bearings were "...intact, oil wetted and rotated free and smooth." Leak check of the pneumatic system revealed no leaks.

Failure analysis personnel of the engine manufacturer examined damaged and fractured hardware to include the fractured compressor blades and vanes, as well as the vanes and blade of the first stage turbine nozzle and first stage turbine wheel, respectively. The damaged compressor blades and vanes all exhibited evidence of overload failure, while the vanes and blade of the first stage turbine nozzle and first stage turbine wheel exhibited impact and temperature damage. The damaged main drive shaft was retained for further examination by the NTSB Materials Laboratory (NTSB Met Lab) located in Washington, D.C.

Metallurgical examination of the main drive shaft by the NTSB Met Lab revealed the forward flexible coupling fractured into a number of pieces, while the aft flexible coupling fractured in 5 locations which allowed separation of the fitting from the shaft. One "frame" and a section of one of the "...shorter legs of one frame..." of the forward flexible coupling was not located nor submitted for examination while all pieces of the aft flexible coupling were located/submitted. Examination of all fracture surfaces revealed all exhibited features consistent with overstress, with no evidence of preexisting failure or malfunction. All the bolted connections for the forward and aft flexible couplings were "intact." Rotational scoring was noted on the forward and aft halves of the main drive shaft, the forward flexible coupling, and on the fractured pieces of the forward coupling, while negligible rotational scoring was noted on the aft fitting.

A review of the provided maintenance records revealed that from September 17, 1987, to October 3, 2000, the engine was installed in another helicopter and had accumulated 1,853 hours since new and 1,115 hours since overhaul. The engine was removed for repair on October 3, 2000, and the gearbox assembly, compressor assembly, and turbine assembly were inspected and repaired as necessary. The engine was preserved for long-term storage. The engine was removed from long-term storage, inspected as necessary, and installed in the accident helicopter on January 13, 2003. The engine remained installed in the accident helicopter from that date until postaccident removal. At the time of the accident the engine had accumulated 2,291.2 hours since new, 1,553.2 hours since overhaul, and 438.2 hours since installation into the accident helicopter.

The helicopter minus the NTSB retained engine and KAflex drive shaft was released to Major Chuck West of the St. Johns County Sheriff's Office on October 11, 2005. The retained engine and KAflex driveshaft were also released to Major West on September 6, 2006.

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