Sikorsky S-76A N176SH accident near Grand Rapids, Michigan

Probable cause

The pilot's failure to maintain tail rotor obstacle clearance from a tower during takeoff.

NTSB analysis

The air ambulance helicopter was departing from a hospital heliport that was located on the 11th story of the hospital during an FAA Part 135 check. Before takeoff, the pilots discussed the construction cranes that were operating on the north side of the hospital and their effect on the approach and departure routes to the pad. The pilot reported that he lifted the helicopter straight up into a vertical takeoff. The torque was about 94 percent and "everything was nominal." The helicopter was about 40 feet in the air when the pilot heard a "pop" and the helicopter started to yaw to the right and vibrate. He attempted to land back on the helicopter pad by using the cyclic and lowering the collective, but the main rotor blades impacted the 32-foot high brick structure located east of the helicopter pad. The helicopter fell straight down impacting the hospital roof. Witnesses observed the helicopter lift off the helipad and then fly backwards until the tail rotor hit a tower on top of the roof. A hospital security video camera showed the helicopter fly backwards as it lifted off the helicopter pad. It showed that the tail rotor appeared to strike an object on one of the towers, and the tail rotor immediately shattered and the helicopter went into a right yaw. A camera that was mounted on one of the towers exhibited impact marks and carbon fibers were found lodged in a crevice of the camera body. Based on the analysis of the accident site, the helicopter traveled about 61 feet straight-line distance rearwards at an angle of about 41-51 degrees relative to the hospital pad. The time from takeoff to impact with the camera was about 11.37 seconds. The inspection of the helicopter revealed no preexisting anomalies that would preclude normal operation.

Text from the NTSB. Open the NTSB docket for CHI08FA141 for the full record.