What happened
A pilot was conducting a night VFR traffic pattern for a full stop at a non-towered airport in a turboprop aircraft. The flight entered the traffic pattern at 6,800 feet (1,000 feet AGL) on an extended downwind leg, with radar data showing an initial ground speed of 205 knots. Over the following 3 nautical miles on the downwind, the pilot slowed to 171 knots, lost approximately 500 feet of altitude, and reduced the parallel distance from the runway from 4,775 feet to 2,775 feet. Witnesses reported that radio transmissions on the CTAF appeared normal, but observed a bright blue flash followed by a loss of contact with the aircraft.
Due to the darkness, ground rescue personnel were unable to locate the wreckage immediately; however, a police helicopter located the airplane approximately two hours after the accident. The pilot was 1 fatality.
The investigation
Investigators found a broken and downed static wire from a system of three sets of power transmission wires. This wire was located 8,260 feet from the runway threshold and sat approximately 30 feet higher than the threshold. Post-accident examinations of the aircraft and its engine revealed no mechanical anomalies that would have prevented normal operations prior to impact.
Radar data indicated that during the turn from base to final, the pilot was in a maximum descent of 1,800 to 1,900 feet per minute with an airspeed on final of 145 to 150 knots. The pilot's maximum bank angle during this turn was calculated to be more than 70 degrees.
Findings
- The pilot had recently completed factory-approved annual flight training.
- Training instructions provided by the flight instructor specified that VFR traffic patterns should be flown at 1,500 feet AGL (500 feet above piston-powered aircraft).
- Standard procedures taught to the pilot included entering the downwind leg from a 45-degree leg and maintaining approximately 1 to 1.5 nautical miles of separation from the runway.
- Target speeds for a stabilized approach were indicated at 145 to 150 knots on downwind and 90 to 95 knots on final.
- The instructor also specified that the base turn should not exceed a maximum bank angle of 30 degrees.