WPR18LA041 · Robinson Helicopter Company R22 MARINER

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.

Verbatim NTSB analysis and probable cause from the NTSB dataset