NTSB Releases Probable Cause Report

The NTSB has released its probable cause report for a mid-air collision in January, 2008 which killed four people in two aircraft and one on the ground. The incident, which happened January 20th of last year, involved a Cessna 150, piloted by 24-year-old  Anthony Guzman, and a Cessna 172, flown by 73-year-old Paul Carson. Both pilots were instrument rated, though the accident happened under VFR conditions.

The NTSB found:

A Cessna 172N and a Cessna 150M collided in-flight while maneuvering 1.4 miles southwest of the uncontrolled airport during day visual meteorological conditions. The midair collision occurred about 2 minutes after the Cessna 150M had taken off from runway 25, turned crosswind, and was entering on the downwind leg.

Radar data shows that during this time, a Cessna 172N completed a course change maneuver and was proceeding inbound toward the airport on a 034-degree true course, which approximated the 45-degree traffic pattern's entry path to the downwind leg. The north-northeast-bound Cessna 172N impacted the right side of the southeast-bound Cessna 150M after the airplanes were flying on converging courses for about 13 seconds. The collision angle was about 70 degrees. The four occupants in the airplanes and one person on the ground were killed.

Calculations based on radar data show that the Cessna 150M pilot turned onto the crosswind leg prior to reaching 700 feet above ground level, which is contrary to the Federal Aviation Administration's recommended procedures. A visibility study determined that while on the crosswind leg and during the turn onto the downwind leg, the Cessna 150M pilot had 14-second window of opportunity to observe the approaching  Cessna 172N, which was travelling at 106 knots (ground speed), but was likely not able to see it in the final 9 seconds prior to the collision as the Cessna 150 was turning left onto the downwind leg. According to Cessna, the field of view (visual angle) from the cockpit of the Cessna 150M as it was turning to the downwind was limited in the area from which the Cessna 172N was converging by the door post structures. As the Cessna 172N's pilot was approaching the airport, the Cessna 150M, which was travelling at 74 knots (ground speed), would have been in his view at the 10:30 to 11:00 o'clock position and low in the windscreen.

A witness reported that neither airplane appeared to alter its course during the final seconds of flight. No airport facilities or any of the pilots flying in the vicinity reported hearing any communication from either airplane.

FMI: http://www.ntsb.gov