NTSB releases preliminary report on Dallas midair

The P–63F was No. 3 in a three-ship formation of fighters, and the B–17 was leading a five-ship formation of bombers. Both formations had been instructed to "maneuver southwest of the runway before returning to the flying display area," the NTSB preliminary report said. The air boss "directed the fighter formation to transition to a trail formation, fly in front of the bomber formation, and proceed near the 500 ft show line. The bombers were directed to fly down the 1,000 ft show line."

The FAA establishes show lines for performances in front of crowds. AOPA Air Safety Institute Senior Vice President Richard McSpadden explained show lines in the Early Analysis of the accident. The lines run parallel to the crowd so that spectators can view the flight activity. The FAA establishes show line distances based on several factors, McSpadden said, including the aircraft type, speed, and the types of maneuvers being performed, with the closest line being at least 500 feet from spectators.

The NTSB preliminary report indicates that the fighters would have been 500 feet from the airshow viewing line and the bombers 1,000 feet from the line.

The preliminary report noted that "there were no altitude deconflictions briefed before the flight or while the airplanes were in the air." However, altitude deconfliction is not always used to determine separation during an airshow. McSpadden said that aircraft can be separated sequentially, laterally, or by altitude and that it is not necessary to have all three. In this case, the aircraft had sequential separation with the fighter formation instructed to fly in front of the bomber formation and lateral separation with the two different show lines. He also explained that it is common not to have altitude deconflictions so that pilots can look outside at visual references instead of focusing in the cockpit on their altimeter.

The P–63 was in a left bank when it collided with the B–17, hitting the left side of the aircraft just behind the wing. The B–17's wing center section caught fire as it fell to the ground, and the bomber exploded upon impact near the approach end of Runway 31.

The NTSB Vehicle Recorders Laboratory has the B–17's Avidyne IFD540, which "contained position information relevant to the accident." The P-63's Garmin GPSMAP 496 was also recovered but "did not record any information for the accident flight."

The NTSB retained the wreckage of both aircraft for further investigation. Information in the preliminary report is subject to change as more facts are uncovered during the investigation. A probable cause should be released 12 to 18 months after the accident, the NTSB said during an early press conference after the accident.