WPR18LA041

The flight instructor was demonstrating an autorotation with a 180° left turn at a density altitude of about 6,470 ft. He entered the maneuver from 700 ft above ground level (agl) and about 80 kts indicated airspeed, established engine rpm, and started the 180° turn. About 1/3 of the way through the turn, he felt he needed a “desirable” speed through the turn and moved the cyclic forward and adjusted the collectively accordingly. The flight instructor stated that when he should have been 2/3 through the turn, he felt that he did not have the cyclic and collective control of the helicopter and he knew they were going to crash. He further stated that he continued “teaching,” and called out “rpm, airspeed, and outside,” while pointing to the tachometer, airspeed indicator, and intended landing spot; he also made control inputs and continued to fly what “had become an unresponsive aircraft.” He also stated that there was no flare at the end of the autorotation and no time for an engine rpm recovery. Postaccident examination of the airframe and engine revealed no mechanical anomalies that would have precluded normal operation. The helicopter manufacturer’s Safety Notice SN-38 stated that if any of the parameters for rotor rpm, a stabilized airspeed, a stabilized rate of descent or turns (if any) completed are not correct, an immediate power recovery should be initiated; salvaging the situation by coaching the student or trying to correct below 100 ft agl (200 ft when operating at or above 4000 ft density altitude) should not be attempted. Had the flight instructor aborted the autorotation early on, it is likely he would have regained helicopter control.

On November 30, 2017, at 1540 Pacific standard time, a Robinson Helicopter Company (RHC) R22, N47WH, was substantially damaged when it was involved in an accident near Truckee, California. The two pilots were seriously injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor reported that the pilot/owner had just purchased the helicopter and it was delivered the morning of the accident. The flight instructor had flown the helicopter earlier in the day to comply with his recent flight experience requirements. The accident occurred in the afternoon, with the owner of the helicopter also onboard. The purpose of the afternoon flight was to check out the flight characteristics with two full size adults on board to determine if it could serve as a viable training helicopter for the operator. If the helicopter performed well, then he and the owner would practice some procedures and maneuvers required for a biennial flight review for the owner. According to the flight instructor they practiced several different maneuvers, normal takeoffs, pattern work, normal approaches, steep approaches, landings, hover work, governor off work, hovering autorotations, and low rpm recovery in a hover. The flight instructor stated that the flight went well, and they decided to do straight-in autorotations as well as 180° autorotations. After completion of the straight-in autorotations, they moved on to 180° autorotations. The flight instructor set up for a 180° autorotation; while on downwind they commented that the helicopter was not flying smoothly and thought the main rotor was unbalanced and had a “little hop.” He had not noticed the vibration on the earlier flights. They continued with the flight and the maneuver. After they passed the intended landing point, he entered from 700 ft above ground level (agl) and about 80 kts indicated airspeed, he established his rpm, and started the 180° turn. About 1/3 of the way through the turn, he felt he needed a “desirable” speed through the turn and moved the cyclic forward and adjusted the collectively accordingly. The flight instructor stated that when he should have been 2/3 through the turn, he felt that he did not have the cyclic and collective control of the helicopter and he knew they were going to crash. He further stated that he continued “teaching,” and called out “rpm, airspeed, and outside,” while pointing to the tachometer, airspeed indicator, and intended landing spot; he also made control inputs and continued to fly what “had become an unresponsive aircraft.” The flight instructor stated that there was no flare at the end of the autorotation and no time for an engine rpm recovery. A witness at the airport watched the helicopter practicing pattern work east of runway 29. He saw the helicopter turn onto its base leg at a normal attitude and then it entered a rapid descent toward the runway. The witness reported that the helicopter flaredabout 30 yards from the runway, impacted the ground, tail rotor first, followed by the main body of the helicopter. The main rotor blades sheared off the tail boom and the helicopter came to rest on its side. Postaccident examination of the airframe established flight control continuity. The tail cone separated after contact by a main rotor blade. The throttle linkage was intact and in the closed position. The mixture was full rich, and the carburetor heat was in the OFF position. Both V-belts were out of the sheave grooves. One V-belt was fractured across the vees. The fuel tanks were half-full as verified visually and by the fuel gauges. The engine sustained minimal impact damage. The crankshaft rotated by hand using the cooling fan with no anomalies noted. Thumb compression was established in all cylinders, and spark was produced at the lower ignition leads during rotation of the crankshaft. The automated weather observation station at the Truckee-Tahoe Airport (TRK), Truckee, California, reported at 1545 wind from 290° at 5 knots, temperature 50°, dewpoint 23°, and altimeter setting of 30.17 inches of mercury. TRK was located at an elevation of 5,904.3 ft mean sea level (msl); density altitude was calculated to be 6,469 ft. The maximum gross takeoff weight for the R22 Beta II is 1,370 lbs. The estimated gross weight at the time of the accident was calculated to be about 1,356 lbs. Information pertaining to the execution of autorotations can be found in the Helicopter Flying Handbook, as well as the FAA Practical Test Standard, Private Pilot Rotorcraft, along with additional information from RHC Safety Notice SN-38, Practice Autorotations Cause Many Training Accidents. SN-38, in part, indicated a 100 ft decision check that identified rotor rpm, stabilized airspeed, stabilized rate of descent, and turns. An immediate power recovery should be made if any of the parameters are not correct. It also stated that there should be no attempt to salvage the situation by coaching the student or trying to correct below 100 ft above ground level (agl). At density altitudes above 4,000 ft, the decision height should be increased to 200 ft above the ground or higher. The safety notice also indicated that practice should be limited to no more than three or four consecutive autorotations to maintain instructor focus and minimize student fatigue.