Madill, OK, USA
N7782H
Robinson R22
The pilot reported that about 10 minutes after takeoff, the helicopter was in level flight about 700 to 800 ft above ground level when the clutch actuator warning/caution light illuminated. He entered an autorotation intending to do a power recovery close to the ground. He indicated that, within a "short second or two" after the clutch light illuminated, he heard a "bang" and felt the helicopter shudder. He continued the autorotation and landed on rough terrain. The helicopter rolled onto its left side and sustained substantial damage to the tail boom, main rotor, and fuselage. The examination of the helicopter revealed that the two double V-belts had separated from the upper sheave and that there was a field repair on the wire connections at the clutch actuator fuse holder. The terminals were wrapped in tape and a wire tie. When the wire tie and tape were removed, the fuse holder terminal fell and fractured from the holder, and the wires separated from the solder on the terminal. The extension limiter was found at 1.65 inches, which is the maximum extension limit; the normal range was 1.1 to 1.3 inches. The improper repair of the clutch actuator fuse holder likely caused the loose condition of the V-belts, which resulted in V-belt failure and the loss of power to the helicopter's rotor system, subsequent autorotation, and forced landing.
On March 20, 2019, about 1610 central daylight time, a Robinson R22 Beta II helicopter, N7782H, sustained substantial damage during an emergency landing to a field near Madill, Oklahoma. The pilot was not injured. The helicopter was owned and operated by Rocking R Enterprises under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which was not on a flight plan. The flight departed the Madill Municipal Airport (1F4), Madill, Oklahoma, about 1600 and was en route to the Ardmore Municipal Airport (ARD), Ardmore, Oklahoma. The pilot reported that he conducted a preflight of the helicopter which included checking the condition of the V-belts that drive the rotor, and they appeared to be normal and with the proper deflection (approximately 1 ½ inches). About 10 minutes after takeoff, he was in level flight about 700 to 800 ft above ground level, when the clutch light warning light illuminated. He entered an autorotation intending to do a power recovery close to the ground. However, within a "short second or two" after the clutch light illuminated, he heard a "bang" and felt the helicopter shudder. He continued the autorotation and landed in a pasture that was rough. The helicopter rolled onto its left side and sustained substantial damage to the tail boom, main rotor, and fuselage. The examination of the helicopter revealed no preexisting anomalies to the engine, rotor system, and flight controls. However, the examination revealed that one of the two double V-belts was missing; and one belt of the other double V-belt was also missing. They were not located at the accident site. The remaining V-belt was displaced from the upper sheave and was found hanging on the output shaft. Black rubber marks were found on the clutch actuator, the forward face of the upper sheave, the centering strut, and on the frame tubes adjacent to the V-belt grooves. The examination revealed that there was a field repair on the wire connections at the clutch actuator fuse holder. The terminals were wrapped in tape and a wire tie. When the wire tie and tape were removed, the fuse holder terminal fell, fractured from the holder and the wires separated from the blob of solder on the terminal. The clutch actuator fuse was removed, and it was a 2-amp fuse instead of the specified 1.5-amp fuse. The extension limiter was found at 1.65 inches, which is the maximum extension limit; whereas, the normal range was 1.1 to 1.3 inches. The maintenance logbook indicated that the last annual maintenance inspection was performed on December 5, 2018. The helicopter total time at the time of the inspection was 6,438.2 hours with an hour meter reading of 4,243.9 hours. The helicopter hour meter was 4259.4 hours at the accident site. The helicopter had operated 15.5 hours since the last annual inspection. The Robinson R22 Series Pilot Operating Handbook stated the following concerning the clutch actuator: "After the engine is started, it is coupled to the rotor drive system through V-belts which are tensioned by raising the upper drive sheave. An electric actuator, located between the drive sheaves, raises the upper sheave when the pilot engages the clutch switch. The actuator senses compression load (belt tension) and switches off when the V-belts are properly tensioned. The clutch caution light illuminates whenever the actuator is energized, either engaging, disengaging, or retentioning the belts. The light stays on until the belts are properly tensioned or completely disengaged. Belt slack during engine start should be adjusted such that blades begin turning within 5 seconds of clutch engagement. Excessive slack may cause belts to jump out of the sheave grooves during start. Periodic readjustment by a mechanic may be required as belts wear in service. A fuse located on or near the test switch panel prevents an actuator motor overload from tripping the circuit breaker and turning off the caution light prematurely. CAUTION Never take off while clutch light is on." The Robinson R22 Series Pilot Operating Handbook stated the following concerning the clutch actuator warning/caution light: Clutch Light Warning: Indicates clutch actuator circuit is on, either engaging or disengaging clutch. When switch is in the ENGAGE position, light stays on until belts are properly tensioned. Never takeoff before the light goes out. NOTE Clutch light may come on momentarily during run-up or during flight (approximately 3 to 6 seconds) to retention belts as they warm-up and stretch slightly. This is normal. If, however, the flight flickers or comes on in flight and does no go out within 10 seconds, pull CLUTCH circuit breaker and land as soon as practical. Reduce power and land immediately if there are other indications of drive system failure (be prepared to enter autorotation). Inspect drive system for a possible malfunction.
The failure of the V-belts due to improper maintenance, which resulted in the loss of power to the helicopter's rotor system and subsequent forced landing on rough terrain.
Source: NTSB Aviation Accident Database
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