BOULDER COUNTY, Colo. — A preliminary report on a mid-air plane crash that killed three people in Boulder County in September has been released by the National Safety Transportation Board.
The Cessna 172S and Sonex Aircraft Xenos crashed in mid-air at 8:53 a.m. on Sept. 17 near Longmont, according to the NTSB report.
The Cessna was carrying a flight instructor and student pilot. A pilot was using the Sonex — which was listed as "amateur built" — for a personal flight. All three died in the crash.
Based on air traffic control flight track data, investigators learned the pilot of the Cessna took off from the Rocky Mountain Municipal Airport in Denver at 8:43 a.m. and the Sonex left the Platte Valley Airpark in Hudson at 8:38 a.m. Both planes, operating under visual flight rules, climbed to about 7,000 to 7,500 feet above sea level — or roughly 2,000 feet above the ground, according to the report. Neither was in contact with air traffic control (ATC), but they were not required to, according to the report.
The pilot of the Cessna flew northbound and the Sonex headed west toward Longmont.
The pilot of the Cessna made a 360-degree left turn and then headed eastbound, the report said.
Shortly after this, the flight track data of the planes intersected and then showed both rapidly descending. They impacted nose-down in a rural area around N. 95th Street and Niwot Road, according to the report.
The left wings of both planes were found in a field below where the flight tracks merged. The Cessna's main wreckage site was found in a field about 1,800 feet southwest of the wing pieces. The main wreckage from the Sonex was found about 1,100 feet southwest of the fragments, according to the report.
According to the report, both planes were required to transmit an automatic dependent surveillance broadcast. This ADS-B technology provides continuous updates on a plane’s location using navigation satellites to other planes and air traffic controllers, according to the Associated Press.
The Cessna was equipped with, and transmitted, ADS–B. The pilot of the Sonex did not transmit this data.
On Sept. 19, the Boulder County Coroner’s Office identified the deceased as:
- Daniel Wilmoth, 22
- Samuel Fisher, 23
- Henry Butler, 69
The full report could take 12 to 18 months to complete. The NTSB asks any witnesses with information to email witness@ntsb.gov.