History of Flight
On February 11, 2010, at approximately 2236 Eastern Standard Time, a Eurocopter AS 365 N2, registration N61MD, operated by the Maryland State Police Aviation Command (MSPAC), sustained substantial damage when its fenestron (shrouded tail rotor) contacted a snow bank on the ground-level helipad (H1) at Prince George's General Hospital (1MD4) in Cheverly, Maryland. The commercial pilot and the pilot-rated flight paramedic were not injured. The flight was a public medical evacuation operating in night visual meteorological conditions; no flight plan was filed.
The helicopter departed Andrews Air Force Base (ADW) at approximately 2112 under visual flight rules to retrieve two patients from an automobile accident site. After loading the patients, it departed for the hospital around 2200. En route, hospital personnel advised the pilot to land on the ground-level helipad due to ice on the elevated rooftop pad.
The pilot approached from the south-southeast for noise abatement and due to reported winds. During final approach, he observed the pad was clear of snow but had snow banks around its perimeter, with a cleared path for hospital personnel. He performed a high hover with a straight letdown, landing at about 2212 facing slightly south of west. After landing, the flight paramedic and receiving team offloaded the patients; the pilot shut down the helicopter normally and joined the paramedic in the hospital.
At approximately 2229, the crew returned to the helicopter and found the fenestron resting on a snow bank about 3 feet high. The pilot inspected and detected no damage. The flight paramedic suggested removing snow beneath the fenestron, but the pilot decided to attempt a straight vertical takeoff with no yaw movement. After engine start, at about 2236, during a slow deliberate takeoff, a vibration was felt from the rear of the aircraft. The pilot lowered the collective, shut down both engines, and applied the rotor brake.
Post-accident examination revealed severe damage to the tail rotor blades, fenestron, tail rotor gearbox, and mounting structure. The pilot reported that the fenestron was severely damaged by the tail rotor blades, and the right tail rotor gearbox cap appeared to have been ingested.
Personnel Information
FAA records showed the pilot held a commercial pilot certificate with rotorcraft helicopter and instrument helicopter ratings, and a second-class medical certificate issued in June 2009. MSPAC reported he had 2,452 total flight hours, including 360 hours in the accident make/model. He had 25 hours in the preceding 90 days and 6 hours in the preceding 30 days. The flight paramedic held a private pilot certificate with multiple ratings, including rotorcraft helicopter.
Aircraft Information
The helicopter was manufactured in 1993 and registered to MSPAC in 1995. It was equipped with two Turbomeca Arriel turboshaft engines, a single main rotor, and a fenestron tail rotor. The landing gear was tricycle-style retractable. The overall length was 45.1 feet, main rotor diameter 39.2 feet, fuselage length 38.2 feet, fenestron ground clearance 2.2 feet, and the pilot's station was about 32 feet forward of the fenestron. The helicopter was within weight and balance limits for both arrival and attempted departure.
Meteorological Information
The 2255 automated weather observation at ADW (7 miles south) recorded wind from 310° at 9 knots, visibility 10 miles, clear skies, temperature -2°C, dew point -7°C, and altimeter 29.88 inHg.
Heliport Information
1MD4 had two helipads: ground-level H1 (67x67 feet per FAA database) and rooftop H2 (40x40 feet). The ground pad was equipped with perimeter lights and a lighted wind indicator. A brick hospital wall was about 20 feet west of the pad's west edge. The paved surface was black with a 3-foot-wide white perimeter stripe. NOTAMs obtained by the pilot included snow banks at local airports but not at 1MD4.
Additional Information
Hospital surveillance imagery captured the arrival and attempted departure. The camera showed the helicopter approaching from the southwest at 2211:21, landing at 2212:02.5 with a white cloud at the fenestron. After unloading, the crew returned at 2229:45 and inspected the fenestron without auxiliary lighting. At 2236:26, liftoff began; at 2236:40, a large white cloud appeared, and the helicopter rolled right and yawed nose left about 10 degrees before stabilizing.
MSPAC's Landing Zone Directory contained helipad data from the FAA database. After the accident, MSPAC issued a Flight Safety Bulletin urging caution after heavy snow. The hospital's snow removal practices had been unchanged for years; snow banks 2-5 feet high bounded the pad, obscuring perimeter stripes. The cleared area was about 59 feet long, which was shorter than the FAA-recommended minimum TLOF dimension of 67.5 feet. Subsequent measurement confirmed the published pad dimensions were incorrect; the actual pad length was about 11 feet shorter. The FAA and MSPAC databases were later corrected.
FAA Advisory Circular 150/5390-2B recommended keeping TLOF, FATO, and safety areas free of snow and that snow removal not create obstruction hazards. The hospital's snow removal did not follow this guidance; snow from the TLOF was deposited onto the FATO, creating banks that obstructed the tail rotor.