Incident Overview
During an annual standardization check ride in a public-use helicopter, the check pilot evaluated a simulated hydraulic failure maneuver. The maneuver was intended to culminate in a run-on landing. The incident occurred when the helicopter, after initiating the simulation, experienced a rapid left yaw and subsequent rotor strike.
Maneuver Sequence
The evaluated pilot established an out-of-ground-effect hover on the downwind leg. The check pilot then engaged the hydraulic test button to simulate a failure. The evaluated pilot lowered the nose and built forward airspeed to maintain control. After stabilizing flight on the downwind leg, the check pilot disengaged the test button and moved the hydraulic cutoff switch to the off position, fully disabling the hydraulic system. The evaluated pilot maintained control and initiated a shallow approach, descending to about three feet above the runway.
Incident Description
Over the runway, the evaluated pilot allowed the helicopter's airspeed to decrease. The check pilot instructed, "Keep the speed up." In response, the evaluated pilot lowered the nose, but an uncontrollable rapid left yaw developed. The check pilot took over the controls, attempting to keep the helicopter over the runway. However, the nose pitched down, and the main rotor blades struck the ground. The check pilot then reduced the fuel control, and the helicopter settled upright on the runway.
Damage
The helicopter sustained substantial damage to the windscreen above the cabin, the tailboom, and the tail rotor drive system.
Environmental Conditions
Weather recorded at the accident airport at the time of the incident included wind from 250 degrees at 3 knots, clear skies, and a temperature of 72°F.
Guidance from Operator's Flight Manual
The Operator's Flight Manual stated that in case of loss of hydraulic pressure, the recommended safety speed range is 40 to 60 knots. A caution noted that hover flight or low-speed maneuvers should not be attempted without hydraulic pressure assistance, warning of rapid changes in control feedback forces, excessive pilot workload, poor aircraft control, and possible loss of control.
Investigation Findings
No mechanical malfunctions or anomalies were identified as a result of the investigation.