Takeoff and Maneuver
The medevac helicopter lifted off from the hospital's rooftop helipad at night. During the departure, the pilot executed a right pedal turn to the northwest. This maneuver brought the helicopter facing a building that extended approximately 10 feet above the height of the helipad.
Proximity to Building
According to the paramedic, when the helicopter reached about 20 feet above the helipad, he was programming the GPS receiver. At that moment, a "sudden gust" of wind pushed the helicopter from directly behind. The paramedic stated he was not alerted to anything unusual until he looked up and noticed the helicopter's close proximity to a 16-floor brick building located at the northern corner of the heliport. This building extended above the helipad by 4 floors.
Avoidance Maneuver and Impact
The paramedic yelled "building, building, building!" to alert the pilot. In response, the pilot made a rapid right cyclic input in an attempt to avoid hitting the building. However, the helicopter struck the building and subsequently fell approximately 13 floors to ground level.
Paramedic's Observations
The paramedic reported that he did not see or hear any warning lights, horns, or unusual noises before the accident. He was not aware of any mechanical problems with the helicopter.
Wind Conditions
A police officer who had flown two missions in the local area prior to the accident reported that the wind speed at 500 feet above ground level was at least 25 knots and gusting from the south/southwest. After the accident, he stood on the primary helipad and noted that mechanical turbulence from the building was evident. An FAA inspector also stood on the rooftop helipad after the accident and stated that wind gusts were approximately 20-30 knots from the southwest, and they swirled around the heliport.
Flight Manual Limitations
Review of the helicopter flight manual revealed a limitation: "Directional controllability during take-off and landing is assured for flight condition with crosswind components up to 17 [knots]."