Zebulon, GA, USA
N942SC
BELL OH 58C
The flight instructor was providing training to a student pilot during a local public flight. According to the flight instructor, during the fifth simulated engine failure of the flight, the helicopter throttle was advanced for the power recovery. The engine then accelerated, and the engine and rotor tachometer needles were in their normal operating range. At that time, the flight instructor initiated a climb. About 4 to 5 seconds into the climb, when the speed was about 25 knots and the helicopter was at an altitude of 125 ft above ground level, the engine lost power. The instructor made a forced landing into a field, which resulted in substantial damage to the tailboom. Postaccident examination of the helicopter showed proper throttle continuity and rigging as well as fuel system continuity. The engine was placed in a test cell, and the engine started immediately, accelerated smoothly, and ran continuously throughout the test protocol prescribed by the manufacturer. All measured performance parameters were within the manufacturer's acceptable range, which demonstrated that the engine, fuel control, and governor functioned as designed. The available evidence indicated that the throttle was likely not fully opened at the initiation of the power recovery and that, when collective pitch was applied, the fuel control (while governed) could not provide the fuel required to sustain the climb. A decay of engine and rotor rpm resulted, which likely led to the instructor's perception that the engine had failed and his subsequent decision to make a forced landing. The altitude and time available at the point of the perceived failure was likely inadequate to overcome the time requirements for throttle inputs and turbine lag.
On January 29, 2018, about 1725 eastern standard time, a Bell OH-58C, N942SC, operated by the Spalding County Sheriff's Department, was substantially damaged during a hard landing after a loss of engine power near Zebulon, Georgia. The certificated flight instructor and the student pilot were not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local public use instructional flight.In written statement and a telephone interview, the instructor stated the purpose of the flight was to provide flight training to a sheriff's department detective. He said that the accident occurred at the completion of the 5th simulated engine failure of the flight. When the throttle was advanced for the power recovery, the engine accelerated and the engine and rotor tachometer needles "joined" in the normal operating range of the dual engine/rotor tachometer. Once normal operating rpm was achieved for the engine and rotor, the instructor initiated a climb. Approximately "4 to 5 seconds" into the climb, and about 25 knots and 125 feet above ground level, there was a "loss of power from the engine." The instructor stated he checked the throttle position and crossed checked the dual tachometer. He said the engine rpm had decayed to 70 percent, and he reduced collective pitch to maintain rotor rpm. He then cycled the throttle to idle and back to full open, but sensed no corresponding response from the engine. The instructor selected a field and completed the forced landing. He said that due to "low rotor rpm" he performed an aggressive flare to build rpm and cushion the landing. The tail of one skid along with the tail stinger struck the ground and the main rotor contacted the tailboom before the helicopter came to rest upright. The instructor held a commercial pilot certificate with ratings for airplane single engine land, rotorcraft-helicopter, as well as instrument airplane and helicopter. He held a flight instructor certificate with the same ratings. His most recent Federal Aviation Administration (FAA) third-class medical certificate was issued March 22, 2016. The pilot estimated he had 5,800 total hours of flight experience of which 200 hours were in the OH-58C. The helicopter was manufactured in 1968 for the United States Army and was acquired by the Spalding County Sheriff's Department for public use. It was maintained under an annual inspection program. The most recent annual inspection was completed July 14, 2017 at 8,596 total aircraft hours and had accrued 56.9 hours since that date. At 1755, the weather reported at Griffin-Spalding County Airport (6A2), 6 miles northeast of the accident site included clear skies, 10 miles visibility, and winds from 350 degrees at 8 knots gusting to 19 knots. The temperature was 14° C, the dewpoint was -7° C, and the altimeter setting was 30.08 inches of mercury. The wreckage was examined at the accident site by an FAA inspector and all major components were accounted for at the scene. Examination of photographs revealed substantial damage to the tailboom near the fuselage (buckling) and evidence of a strike to the tail rotor driveshaft cover. Continuity of flight and engine controls was confirmed by an airframe and powerplant mechanic. The helicopter was retained for further examination. Detailed examination of the helicopter confirmed proper throttle continuity and rigging. The throttle position was measured at the fuel control across a 90-degree arc. Idle cut-off was 0-5 degrees, ground idle was 30 degrees, and 90 degrees was full throttle. The governor came out of "lock-out" at 39 degrees, but full fuel flow was not available until the throttle was fully open at 90 degrees. The engine was then removed for operational testing. Fuel system continuity and boost-pump pressurization of the system was confirmed, with no leaks noted. The engine was placed in a test cell where it started immediately, accelerated smoothly, and ran continuously without interruption through the entire test protocol prescribed by the manufacturer. The engine successfully completed ground idle, flight-idle, max-continuous-power, and take-off power runs. When corrected for standard atmospheric conditions, the engine yielded performance 6.3% above new-production standards at "low cruise? (300 horsepower), 4.9% above new-production standards at normal cruise (370 horsepower), and 10.5% above new-production standards at maximum (Take-Off) power (420 horsepower). The engine then completed "wave-off" max-power transients where the power was reduced to flight idle and then rapidly increased to take-off power. The engine responded normally and responded with maximum power without surging or hesitation.
The pilot's failure to fully open the throttle before initiating the power recovery in response to a simulated engine failure.
Source: NTSB Aviation Accident Database
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