N23Y

On September 10, 1996, approximately 0850 mountain daylight time, a Bell UH-1H, N23Y, was destroyed during an intentional autorotation at Leadville, Colorado. The commercial pilot in command received minor injuries, and the airline transport rated-designated engineering representative (DER) sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the test flight that originated at Leadville on September 10, approximately 0830.

According to an FAA inspector, the crew was conducting high altitude flight tests pursuant to obtaining two STCs (Supplemental Type Certificates): SR000267, for the T53-L-703 engine installation, and SR00266SE, for the installation of a tractor tail rotor system from a Bell 205.

According to the Pilot/Operator Aircraft Accident Report, the pilot entered an autorotation from an altitude of 200 feet agl (above ground level) and at 8,000 pounds maximum gross weight. The maneuver was entered at 42 kias (knots indicated airspeed) with a one second delay before lowering the collective control. The pilot said he was unable to arrest the descent rate as the helicopter approached the runway at 40 knots. The helicopter struck the ground tail first.

A video camera was used to record the flight tests and showed impact occurring on the centerline of runway 34. The tail boom and both skids separated on impact, and the helicopter skidded on its fuselage for 370 feet before coming to a rest on the left side of the runway. The helicopter was equipped with a self sealing fuel system. There was no fire and minimal fuel spillage.

Further examination of the tape revealed the tail boom stinger struck the ground on at least two previous autorotations. According to one FAA helicopter operations inspector, this was indicative that the pilot was "outside the low end of the height-velocity curve." He said that "either there was insufficient airspeed for the altitude used, or there was insufficient altitude for the airspeed used."