Pilot error combined with air traffic control’s failure to warn two planes preparing to land at Centennial Airport that they were near each other are to blame for a dramatic midair collision in 2021 that caused one aircraft to crash and left another with a gaping hole in its side.
That’s according to a final investigative report by the National Transportation Safety Board, a federal agency that probes airplane crashes, released last week.
No one was injured in the May 12, 2021, collision, which happened near Cherry Creek State Park, but the NTSB’s probe revealed major concerns about aircraft congestion around Centennial Airport, which is surrounded by homes and businesses and is one of the nation’s busiest general aviation airports.
One air traffic controller told federal investigators that the proximity of the parallel runways at the airport is “inherently risky,” while another said they tried alerting a superior that Centennial Airport pilots weren’t being properly warned when they were getting too close to other planes as they prepared to land.
The 2021 crash happened when a twin-propeller Swearingen Metroliner belonging to Key Lime Air, a commercial freight and passenger airline, was struck by a Cirrus SR22, a small, single-engine propeller plane flown by a private pilot.
Both aircraft were preparing to land at Centennial Airport on parallel runways that run north to south and are separated by just 700 feet. The NTSB says the Cirrus, which was flying faster than recommended while preparing to land, made too wide of a turn while lining up with its runway, crossing into the Swearingen’s path and striking the larger plane.
The Cirrus was uncontrollable after the collision, prompting the pilot to deploy a parachute attached to the plane, letting the aircraft float to the ground.
The pilot of the Swearingen, who told the NTSB he felt a “tremendous explosion,” continued his landing even though a large portion of the aircraft’s fuselage was ripped away in the collision.
The NTSB said that while the Cirrus pilot was warned by an air traffic controller about the Swearingen’s proximity, the Swearingen’s pilot was not warned about the Cirrus.
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Pilots often rely on air traffic control to help them avoid other aircraft. Most larger commercial aircraft have onboard traffic collision avoidance systems that warn pilots if they are at risk of colliding with another plane. Smaller or older aircraft, however, don’t always have those systems — and it doesn’t appear either plane involved in the May 2021 crash had one.
“During the approach sequence, the controller working the Swearingen did not issue a traffic advisory to the pilot regarding the location of the Cirrus and the potential conflict,” the NTSB report says. “The issuance of traffic information during simultaneous parallel runway operations was required by (the) Federal Aviation Administration. … The two airplanes were on different tower frequencies and had the controller issued an advisory, the pilot of the Swearingen may have been able to identify the conflict and maneuver his airplane to avoid the collision.”
As part of its investigation, the NTSB interviewed several air traffic controllers assigned to Centennial Airport. Nearly all of them said aircraft congestion and the close proximity of the airport’s parallel runways are a consistent problem and risk.
Brian Johnson, an FAA quality assurance specialist assigned to review events in Denver and Salt Lake City, told the NTSB he had written a report to a supervisor about the lack of air traffic control warnings to planes that were near each other in March 2020.
“He said that he had not received a response or feedback on the risks he had identified,” the NTSB said. “He acknowledged that the traffic advisories at (Centennial Airport) from controllers had improved and that it was a ‘stark difference’ to three years ago. He felt as if the report he submitted just sat in the ‘ether.’”
William Flowers, an operational air traffic control supervisor at Centennial Airport, told the NTSB that the close parallel runway configuration was “inherently risky, but mitigable.”
Liam Carke, another operations manager, said the day of the collision there was “light staffing” at the control tower.
Jennifer Benjamin, an air traffic controller who was working the day of the crash and talking to one of the two pilots of the planes that collided, told the NTSB that the volume of traffic at Centennial Airport is the airport’s biggest problem.
“She stated that she would combat that problem by having more controllers so that they could open more positions and spread the workload better,” the NTSB said.
The Federal Aviation Administration declined to say if any air traffic controllers or the pilot of the Cirrus had been sanctioned because of the crash.
“We do not comment on or confirm FAA personnel issues,” Eva Ngai, a spokeswoman for the FAA, said in a written statement.
There were two people aboard the Cirrus, which had taken off from Centennial Airport about an hour before the crash. The pilot was the only person aboard the Swearingen, which was headed to Centennial Airport from Salida.