What happened
On October 12, 2009, an MD Helicopter 60 and 00N, registration N613BP, performed a hard landing at Gillespie Field Airport (SEE) in San Diego, California. The aircraft, operated by the Department of Homeland Security - Customs and Border Protection, was conducting a public-use training flight to evaluate a factory training pilot's ability to conduct autorotation training.
The flight departed from Brown Field Municipal Airport (SDM) with a gross weight of 3,570 pounds. After performing several successful hovering autorotations and initial traffic patterns, the crew attempted a 180-degree autorotation starting from an altitude of 500 feet above ground level.
During the maneuver, the pilot maintained an airspeed between 85 and 90 knots, intending to use the speed for a more aggressive deceleration flare. However, the rate of descent became excessive, leaving the crew too low to execute a proper flare or power recovery. The pilot attempted to level the aircraft to minimize impact, but the helicopter landed hard on the left side. The left skid collapsed, and the aircraft slid approximately 100 yards along the runway. The training pilot was not injured, while the instructor pilot sustained one minor injury.
The investigation
Mechanical examination of the N613BP did not reveal any pre-impact malfunctions, and flight control continuity was established. The aircraft, a NOTAR design, showed no damage to the tail boom, NOTAR empennage, or fan blades. The landing gear damper attachment structure was torn and deformed due to the left skid spreading and the aft portion of the skids penetrating the fuselage.
Investigators noted that at the aircraft's weight and the day's density altitude, the main rotor RPM should have been above the 106.4 percent limit, necessitating an increase in collective pitch to maintain limits. The investigation found that the pilot had been performing the autorotations at the lower part of the green RPM arc.