Suffolk, VA, USA
N442FA
Robinson R22
The pilot was circling the helicopter near friends, about 600 feet above the ground. After a few turns, as he was departing the area, the pilot noticed that the clutch light was illuminated. About 5 seconds later, he pulled the clutch circuit breaker. At the same time, the engine's rpm "sharply" increased and the main rotor rpm alarm sounded. The pilot immediately lowered the collective and "rolled on the throttle" in an attempt to increase rotor rpm. When that failed, the pilot performed an autorotation to the ground; however, during the descent, he was unable to bring the rotor rpm back into the "green" range. The helicopter landed hard, the skids spread, and a main rotor blade impacted the tail boom. Postaccident examination of the helicopter drive system revealed that the V-drive belts had rolled off the sheaves, but the reason they did so could not be determined.
On November 24, 2007, about 1245 eastern standard time, a Robinson R22, N442FA, was substantially damaged during an autorotation in Suffolk, Virginia. The certificated commercial pilot was not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the flight, which originated in a field in Whaleyville, Virginia, destined for Suffolk Executive Airport (SFQ), Suffolk, Virginia. The personal flight was conducted under 14 Code of Federal Regulations Part 91. According to the pilot, he was circling in an area near friends, about 600 feet above the ground. After a few turns, as he was leveling the helicopter to depart, the pilot noticed that the clutch light was illuminated. About 5 seconds later, he pulled the clutch circuit breaker. At the same time, the engine's rpm "sharply" increased and the main rotor rpm alarm sounded. The pilot immediately lowered the collective and "rolled on the throttle" in an attempt to increase rotor rpm. When that failed, the pilot completed an autorotation to a neighbor's field. The pilot stated that he did not attempt to slide the aircraft on the ground because he didn’t want to risk the chance that one or both of the skids became stuck in uneven terrain. Instead, he "selected to and successfully landed the helicopter solidly on the skids." The pilot further noted that once the rotor rpm had decreased, he was not able to bring it back up into the "green" range during the descent. On November 26, 2007, a Federal Aviation Administration (FAA) inspector examined the helicopter after it had been recovered to the airport. According to the inspector, the V-drive belts appeared to have rolled off the sheaves, and the clutch actuator was engaged. The skids were spread, and the aft portion of the tail boom and the tail rotor drive shaft were separated from the helicopter. The FAA inspector contacted a representative at Robinson Helicopter Company who advised that possible reasons V-drive belts could roll off the sheaves were defective belts, misalignment of the sheaves, excessive wear in the sheave grooves, the helicopter operating over gross weight, or an excessive power setting. The V-drive belts were installed during the last annual inspection, on October 4, 2007, at a total airframe time of 3,872 hours. The serviceability tag noted that a 5-hour bench test had been completed on the belts on July 21, 2006. After photographing the belts, the inspector attempted to reinstall them on the sheaves to check alignment. The belts were damaged to the extent that they would not align within the sheave grooves. On November 28, 2007, the inspector again examined the helicopter. He reinstalled the V-drive belts that were removed during the annual inspection. He then verified that the engine ring gear-to-upper frame cross tube dimensions and the V-drive belts' nominal deflection with the actuator disengaged were within limits, and the clutch actuator readily engaged and disengaged. He also verified that the V-drive belts’ guide and tension measurements were within limits. The sheave alignment was measured at .102 inch on both the right and left sides. The Robinson Maintenance Manual requires the right gap to be .010 to .050 inch and the left gap to be .030 to .070 inch and .010 to .030 inch larger than the right gap. No excessive wear was apparent in the sheave grooves, and there was no corrosion. An inspection of the tapered mating surface on the cooling fan hub and fan drive shaft revealed galling marks. On July 16, 2007, the V-drive belts were examined at Robinson facilities, under Safety Board oversight. The forward drive belt was visually inspected and found to be split along its entire length, with the outer layer missing. There were no additional defects or abnormal wear patterns present, and no identifying lettering. The belt measured 24.314 inches, while the maximum allowable length, when new, was 24.160 inches. Robinson personnel indicated that it was normal for new belts to stretch slightly during the first hours of operation. The aft drive belt was also visually inspected, and exhibited splitting along half of its length. There were no additional defects or abnormal wear patterns present. The belt was marked "Robinson Helicopter A190-2 Rev X," and its length was 24.506 inches. According to Robinson personnel, the aft belt would typically be slightly longer than the forward belt. Robinson personnel also confirmed that both belts exhibited damage consistent with rolling off the drive sheaves. An examination of the clutch actuator (belt tension actuator) revealed a small dent on the bottom edge, but otherwise appeared normal and undamaged. Robinson personnel also noted that the clutch actuator controlled the tension of the drive belts by expanding and contracting, thus increasing and decreasing the distance between the two sets of drive belt sheaves. The actuator was tested, and ceased extending at 1,239 pounds as compared to 1,200 pounds when new. The actuator ceased contracting at 983 pounds, as compared to a minimum of 900 pounds when new. The actuator’s maximum extension length was 1.84 inches, with a maximum allowable length of 1.85 inches. Robinson personnel indicated that the actuator was functioning normally. An additional examination of the helicopter revealed that the upper and lower clutch support bearings rotated smoothly, and that the sprag clutch rotated and freewheeled smoothly. There was no visible damage to the lower belt sheave. The actuator system fuse appeared normal, and electrical continuity was confirmed to the actuator system. The pilot held a commercial pilot certificate for rotorcraft-helicopter, and a private pilot certificate for airplane single engine land. He reported 780 hours of total flight time, with 295 hours in helicopters, and 232 hours in make and model. The pilot also noted that the winds were calm at the time of the accident. According to the Robinson R22 Pilot Operating Handbook, a power failure is defined as either an engine failure or a drive system failure. A drive system failure would be indicated "by an unusual noise or vibration, nose right or left yaw, or decreasing rotor rpm while engine rpm is increasing." A caution also noted: "Avoid using aft cyclic during touchdown or during ground slide to prevent possible blade strike to tailcone." Power failure procedures included lowering the collective immediately to maintain rpm and enter a normal autorotation; establishing a "steady glide" about 65 knots; adjusting collective to keep the rotor rpm in the green arc; beginning a flare about 40 feet above the ground to reduce the rate of descent and forward speed; applying forward collective about 8 feet above the ground to level the helicopter; raising the collective just before touchdown to cushion the landing; and landing in a level attitude with the nose straight ahead.
The V-drive belts' rolling off the sheaves for undetermined reasons, resulting in a loss of power to the rotor system, and the pilot's failure to maintain adequate rotor rpm during the autorotation, resulting in a hard landing.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
