ERA10TA142 · Eurocopter AS 365 N2 DAUPHIN

The hospital was equipped with two helipads; one at ground level and one on the rooftop. The rooftop pad had not been cleared of snow, and the flight was the first to arrive since the ground-level pad was cleared of snow the previous day. According to the pilot of the medical transport flight, while on final approach to the ground-level helipad, he observed that it was clear of snow, but that snow banks 2 to 5 feet high bounded the pad. The pilot intended to land facing a wall that was about 20 feet from the edge of the pad, while leaving sufficient room to allow the medical receiving personnel to safely maneuver themselves, their equipment, and their patients between the front of the helicopter and the snow bank. After the patients were unloaded and the helicopter was secured, the pilot and flight paramedic went into the hospital for about 12 minutes. On their return to the helicopter, the crew observed that the fenestron was in contact with the top of a snow bank. They examined the fenestron and tail rotor, determined that the helicopter was undamaged, and proceeded with boarding and departure activities. During the attempted liftoff, the pilot noticed a vibration from the rear of the aircraft. He lowered the collective, turned off the engine, and exited the helicopter to determine the cause of the vibration. The helicopter sustained damage to the fenestron, tail rotor blades, and tail rotor drive components due to contact with the snow bank.

The hospital used its security and facilities personnel to clear snow from the helipads, but it did not possess or provide them with any formal guidance regarding snow-clearing procedures. Site documentation indicated that the helipad pavement was unmarked, with the exception of a 3-foot wide perimeter stripe. Although compliance was not mandatory, the snow removal was not accomplished in accordance with readily-available Federal Aviation Administration guidance. Snow bank heights and distances from the pad did not provide adequate clearances for operations; the pad pavement was not fully cleared, and the pad perimeter stripe behind the helicopter was completely obscured by a snow bank. The hospital did not issue a Notice to Airmen (NOTAM) regarding the presence of snow banks. The crew's pre-departure examination of the fenestron and tail rotor was superficial and unlikely to detect possible damage. No circumstances that precluded the crew from requesting the removal of additional snow, or rolling the helicopter forward so that the fenestron was clear of the snow bank prior to the attempted departure, were discovered. Examination of security video was inconclusive as to whether the damage was incurred during the arrival, the attempted departure, or both.

Verbatim NTSB analysis and probable cause from the NTSB dataset