The U.S. National Transportation Safety Board (NTSB) says a EUROCOPTER AS365N2, (N61MD) was substantially damaged Feb. 11, 2010 during a takeoff attempt from a ground-level helipad at Prince George's General Hospital (1MD4), Cheverly, MD.

The AS365N2 operated by the Maryland State Police (MSP) was damaged while departing the shock trauma medical facility about 2236 Eastern Standard Time. The commercial pilot and the pilot-rated flight paramedic were not injured. The public medical evacuation flight was being operated in night visual meteorological conditions, and no flight plan was filed.

The emergency medical services (EMS) helicopter had earlier departed Andrews AFB (ADW), Camp Springs, MD, under visual flight rules (VFR), to transport two patients from an automobile accident site to 1MD4. The chopper landed at the accident site, the patients were loaded, and about 2200, the helicopter departed for 1MD4. While enroute to 1MD4, the pilot was advised by hospital personnel to land on the ground-level helipad, due to the presence of ice on the hospital's elevated helipad.

According to the pilot, due to noise abatement procedures and the reported winds at ADW, he approached 1MD4 from the south-southeast. He stated that when he was on final approach to the pad, he observed that it was clear of snow, but that it had snow banks around the perimeter. He also noted that a paved path was cleared of snow to allow the hospital receiving team to access the helipad from the hospital building.

The pilot stated that during the final approach, he was concerned about creating "white out" conditions as the helicopter neared the ground. In addition, he wanted to position the helicopter so that the clearance between the snow banks and the front of the helicopter would permit the receiving team to maneuver around the helicopter.

The pilot stated that "the approach was made to a high hover with straight let down," and that it "was completed to the center of the ground pad to ensure safe clearance for the hospital personnel to safely maneuver to unload the patients."

The helicopter landed about 2209, facing slightly south of west. The pilot stated that "the landing...was accomplished with no incidents detected."

After landing, the flight paramedic and the hospital receiving team offloaded and transported the patients to the hospital emergency room, while the pilot shut down the helicopter. The pilot reported that the shutdown was normal, and after he secured the helicopter, he joined the flight paramedic in the hospital.

About 2229, when the crew returned to the helicopter, the pilot noted that "the crew observed that the aircraft's fenestron (shrouded tail rotor) was resting on top of an a three-foot-high snow bank," and that "further inspection detected no damage to the fenestron." The flight paramedic suggested to the pilot that it might be appropriate to remove some of the snow beneath the fenestron, in order to provide more clearance for the takeoff.

The pilot determined that "since there was no damage" and that "the tail rotor itself was clear of the snow, a straight up take off with no yaw movement would be made." About 2234, engine start was completed, without any anomalies. The pilot stated that "a slow deliberate takeoff was then initiated," and when the helicopter "became light on the wheels, but prior to takeoff, a vibration was detected, emanating from the rear of the aircraft." In response to the vibration, the pilot lowered the collective, shut down both engines, and applied the rotor brake.

The pilot stated that after he shut down and secured the helicopter, he and the flight paramedic visually inspected the helicopter. The pilot stated that the inspection revealed that "the fenestron was severely damaged by the tail rotor blades, the right tail rotor gear box cap appeared to have been ingested by the tail rotor, and numerous tail rotor blades were damaged." Preliminary examination by MSP and Federal Aviation Administration personnel revealed substantial damage to the tail rotor blades, the fenestron, the tail rotor gear box (TGB), the TGB drive coupling, and the TGB mounting structure.

The helicopter was manufactured in 1993, and registered to the MSP in 1995. The landing gear is retractable, tricycle-style, with wheels and tires. The manufacturer's published technical data indicated an overall length of 45.05 feet, fuselage length of 38.15 feet, pilot's station about 32 feet forward of the fenestron, and fenestron ground clearance of 2.17 feet.

1MD4 is equipped with two separate helipads; one at ground level, designated "H1," and one on the hospital rooftop, designated "H2." Helipad elevation was listed as 297 feet above mean sea level. The H1 pad, which is 67 feet square, is equipped with perimeter lights and a lighted wind indicator. The H1 pad is oriented about 10 degrees counter- clockwise from true north-south alignment. The paved pad surface is black in color, and a white stripe, approximately 2 feet wide, is painted around the entire perimeter.

Photographs taken the night of the accident showed that the snow had been cleared to expose the majority of the perimeter stripe, and was pushed into snowbanks that bordered all four sides of the pad. The snowbanks ranged from 2 to 5 feet in height. The path that was cleared through the snow between the pad and the hospital joined the pad near the south end of the west edge.

The pilot held a commercial pilot certificate with rotorcraft helicopter and instrument helicopter ratings. His most recent FAA second-class medical certificate was issued in June 2009.

The pilot had 2,452 total hours of flight experience, including 360 hours in the accident helicopter make and model. He had 25 hours in the helicopter make and model in the 90 days prior to the accident, and six hours in the 30 days prior to the accident.

The flight paramedic held a private pilot certificate with several ratings, including rotorcraft helicopter.