WPR09FA464

The pilot was in the final phase of the landing approach. About 5 feet over the hospital landing pad, the helicopter started to yaw left in an uncommanded fashion. The pilot countered the yaw with right anti torque pedal, which had no effect. He then rapidly lowered the collective and the helicopter landed hard and came to rest facing the opposite direction. Inspection of the helicopter revealed buckled skin on the tail boom approximately 2 feet aft of where the tail boom attaches to the rear structure. Hospital surveillance video captured the landing and showed the helicopter approach the landing spot. The helicopter then yawed left and landed facing the direction it came from. The event spanned about 4 seconds from the beginning of the yaw to the landing. The pilot stated that the winds were out of the west at 2-3 knots. Winds reported at the nearest weather reporting facility (6 miles to the southeast) at the time were 350 degrees at 7 knots. Examination of the helicopter control system revealed no anomalies and all system components functioned appropriately when tested.

HISTORY OF FLIGHT On September 24, 2009, at 1843 mountain standard time, a Eurocopter AS 350 B3, N103LN, suddenly yawed left while a few feet above the landing spot, and landed hard on the hospital landing pad at St Mary's Helistop, Tucson, Arizona. Air Methods operated the medical transport helicopter under the provisions of Title 14 Code of Federal Regulations, Part 135. The airline transport pilot, flight nurse, medic, and patient were not injured. The helicopter was substantially damaged. Visual meteorological conditions prevailed, and a company flight plan had been filed. The pilot reported to the Safety Board investigator-in-charge (IIC) that during the final phase of the landing, the helicopter was about 5 feet over the landing pad at St Mary's Hospital when it started to yaw left in an uncommanded fashion. The pilot countered the yaw with right antitorque pedal, which had no effect. He then rapidly lowered the collective, rolled the throttle off, landed hard, and the helicopter came to rest facing the opposite direction. Inspection of the helicopter revealed buckled skin on the tail boom approximately 2 feet aft of where the tail boom attaches to the rear structure. The pilot reported that the winds were from the west at 2-3 knots, and the helicopter was landing to the west. Tucson International Airport, located 6 nm southeast of St Mary's Helistop, reported at 1853, winds were 350 degrees at 7 knots. Examination by a Federal Aviation Administration (FAA) inspector revealed that all control linkages were in place and control continuity was established between the antitorque pedals, cyclic, and collective to the appropriate flight control surface. The hospital had a surveillance camera system, one camera of which points toward the helicopter landing pad, and recorded the helicopter landing. The video frame rate is approximately one frame per second. At 6:41:34 pm, the recording starts. The view is of a dark screen with landing pad edge lights lit along the edge of the helipad and walkway. At 6:41:42 pm, the helicopter’s landing light comes into view in the upper left side of the recording. The tail boom can be identified as a red light behind the landing light. The helicopter makes a smooth steady approach to the landing spot. At 6:41:53 pm, the red light moves to the left of the image and the landing light moves to the right; the red light becomes a green light and the motion stops at 6:41:57 pm, with the helicopter facing in the direction it was approaching from. The video image depicts the helicopter pivoting approximately 180 degrees over a 4-second period while a few feet above the landing pad. PERSONNEL INFORMATION The pilot, age 60, held an airline transport pilot certificate for airplane multiengine land, and commercial privileges for airplane single-engine land, rotorcraft-helicopter, and instrument-helicopter, issued on September 6, 2009. He held a second-class medical certificate issued on January 14, 2009, with the limitationthat he possess glasses that correct for near vision. The pilot reported on the NTSB Pilot/Operator Accident Report that he had 12,841 hours of flight time, 6,710 hours in rotorcraft, and 204 hours in the AS 350 B3. AIRCRAFT INFORMATION The four seat, single-engine helicopter, serial number (S/N) 3128, was manufactured in 1998, and configured for emergency medical services. It was powered by a Turbomeca Arriel 2B, 747-hp engine. The operator reported on the NTSB Pilot/Operator Accident Report that the last inspection was on July 17, 2009, in accordance with an approved aircraft inspection program (AAIP). Total time on the airframe at the time of the accident was 5,244 hours; total time on the engine was 4,969 hours. TESTS AND RESEARCH Pages of the Vehicle and Engine Multifunction Display (VEMD) screens pertaining to the accident flight were captured using a digital camera. The accident flight was identified as flight 368. There was no failure diagnosis pages associated with flight 368. The most recent flight that had failure diagnosis pages was flight 324, 45 flights prior to the accident flight. Failure diagnosis pages are only generated when an anomaly is detected. The tail rotor servo actuator, part number (P/N) SC5072, serial number (S/N) 1275, was removed from the helicopter under the supervision of a FAA inspector, and sent to the Safety Board (IIC). On December 2, 2009, the servo was examined at Hawker Pacific Aerospace, Sun Valley, California, under the supervision of the Safety Board IIC. The servo was visually examined for damage and leaks; nothing unusual was noted. The servo was then placed in a test fixture, pressurized to 580 psi, and a normal acceptance test was conducted involving 100 extension-retraction cycles. The servo exhibited no leaks, and performed within designed parameters.