NTSB Factual Report

On May 18, 2001, at 0925 central daylight time, a Eurocopter AS-350-B2 helicopter, N311TV, was substantially damaged while landing when it impacted the helipad at the KHOU-TV heliport near Houston, Texas. The helicopter was registered to and operated by U.S. Helicopters Inc., of Marshville, North Carolina. The commercial pilot, sole occupant of the helicopter, sustained minor injuries. Visual meteorological conditions prevailed and a company visual flight rules (VFR) flight plan was filed for the 14 Code of Federal Regulations Part 91 business flight. The local flight originated from the Sugarland Municipal Airport, Houston, Texas, at 0915, and was destined for the KHOU helipad.

According to the pilot, during the approach to the roof top helipad, just as the helicopter crossed over the edge of the building (approximately 15-20 feet above the helipad), the helicopter's controls "became very stiff." He looked at the caution panel and noted that the "HYD" light was illuminated; however, the hydraulic warning horn did not activate. Subsequently, the helicopter impacted the helipad with the right skid, and rolled over onto its right side.

Two FAA inspectors and a representative from American Eurocopter examined the helicopter and the accident site. They reported that the hydraulic cut-off switch, which is located on the collective control, was found in the cut-off position (when the switch is in the cut-off position the hydraulic warning horn will not sound). The switch's red plastic guard was found broken, therefore exposing the switch. The cockpit was examined for shattered pieces of the guard and no pieces were recovered. The emergency responders did not indicate that they had moved the hydraulic cut-off switch. The main rotor servos, the hydraulic pump and hydraulic lines were examined, and no leakage was noted. The hydraulic pump pulley/belt assembly was intact. The belt was examined for thermal damage and slippage marks, and none were observed. The hydraulic pump and regulator/manifold were removed from the helicopter for a functional test. All three main rotor blades were damaged and the engine mounts and the tail rotor drive shaft were separated.

The hydraulic pump and regulator/manifold were functionally tested at American Eurocopter, Grand Prairie, Texas, under supervision of the NTSB. The pump operated within manufacturer's specifications and no anomalies were noted. According to a report provided by American Eurocopter, "the pump provided continuous hydraulic pressure once primed, and the manifold/regulator kept the pressure constant at 40 bars while supplied by the pump."

The helicopter's maintenance logbooks and records were reviewed. On April 21, 2001, the airframe and engine underwent their most recent 100-hour inspections at which time the airframe and engine had accumulated a total of 1,751.3 hours. No additional pertinent logbook entries were noted.

NTSB Probable Cause

the failure of the pilot to maintain control of the helicopter following an inadvertent deactivation of the hydraulic system, during final approach. A contributory factor was the unguarded hydraulic cut-off switch.