Accident Overview
A helicopter conducting a night air medical flight to transport a patient between hospitals collided with up sloping terrain. The accident site was located at an abandoned strip mine in a rural area with few ground structures providing reference lighting. Examination of the wreckage indicated the helicopter impacted the terrain in a level flight attitude.
Flight Crew Statements
During post-accident interviews, the pilot reported remembering picking up the patient and then the helicopter tumbling. The flight nurse and paramedic stated they did not recall any indication of a problem prior to impact.
Airspace and Communication
The destination hospital was located within the Class C airspace of Evansville Regional Airport (EVV). The air traffic control facility at EVV closes at 2300. Between 2328 and 2339, the pilot made 12 attempts to establish contact with approach control as the helicopter approached the Class C airspace. A time zone change had occurred at EVV 16 days before the accident.
Altimeter Anomaly
Examination of the cockpit revealed the altimeter was set to 30.08 inches of mercury. The current altimeter setting was 29.77 inches of mercury, which would result in the altimeter indicating approximately 310 feet higher than the helicopter's actual altitude.
Radar Altimeter Issue
The pilot who had flown the helicopter prior to the accident flight reported that the radar altimeter was operating erratically. Both that pilot and the mechanic who maintained the helicopter stated that the accident pilot had been informed of the problem. Bench testing of the radar altimeter after the accident failed to duplicate the reported erratic operation. The decision height (DH) bug on the radar altimeter was found set to 60 feet; company policy required the DH bug to be set to 500 feet during visual night operations.
Mechanical Examination
Examination of the airframe, engine, and flight controls revealed no mechanical failure or malfunction.