US investigators have found that an Airbus A319 had to take evasive action on take-off at St Petersburg in Florida, to avoid climbing into the path of an inbound light aircraft which was flying an abnormal pattern to another runway.

The inquiry has determined that an air traffic controller failed to scan the runway and local area before allowing a Cessna 337 to enter a right downwind pattern for runway 22, and again when granting take-off clearance to the Allegiant Air A319 from the intersecting runway 18.

“Lack of fully scanning all runways and airspace resulted in the local controller losing situational awareness of the Cessna,” says the US National Transportation Safety Board, in its findings on the 29 April 2021 incident.

The controller had originally instructed the Cessna to enter a left downwind pattern for runway 22, before instructing the A319 to line up on runway 18.

But the controller then advised the Cessna pilot – at the time 2.7nm southwest of the airport, at 1,100ft – to change to a right downwind pattern.

A319 Cessna 337 airprox map-c-NTSB

Source: NTSB

Diagram showing the converging paths of the Cessna (N370SD) and the departing A319 (AAY803)

The inquiry found the Cessna flew the downwind leg at a distance “significantly less” than the defined standard of 0.5-1nm, which meant it was closer than expected to the runway intersections.

Investigators also determined that the pilot did not fly a standard traffic pattern altitude, and was not advised by the controller that this altitude was 1,000ft.

The A319 was cleared for take-off and, with the aircraft fairly light, it rotated about halfway down the runway and climbed quickly.

Radar data showed the Cessna was flying at just 300ft, only 800ft from the runway 22 centreline, when it overflew runway 18 from which the A319 was lifting off.

The A319 captain testified that, as he reached for the landing-gear lever, he saw the Cessna “coming right at us” around 200ft above.

“I immediately called for [the first officer, who was flying] to level off, pointed out the traffic and I left the gear down,” he told the inquiry.

The A319 passed under the Cessna’s flightpath with 100ft vertical and 369ft lateral clearance.

A319 Cessna 337 airprox-c-NTSB

Source: NTSB

Surveillance video captured the moment of closest approach as the A319 levelled

“What’s with the aircraft that we almost just hit?” the crew asked the tower controller, after the encounter.

The controller told the crew that the aircraft which overflew the runway had been at 1,000ft, in a right downwind pattern for runway 22.

But the crew replied: “We had to level off, we were climbing right into them.”

The inquiry says that the Cessna pilot informed that he had the A319 in sight “at all times” during the event.

After flying clear of the conflict the A319 resumed climbing and continued to Norfolk, its destination. The crew subsequently transmitted an ACARS message about the incident to Allegiant, adding: “If I didn’t see him when I reached for [the] gear handle we would have hit him.”

Neither A319 pilot reported receiving an alert from the traffic collision-avoidance system, and the captain did not recall seeing any trafic advisory symbols on his display, as he was monitoring other instruments.

Meteorological data shows good visibility at the time. Investigators concluded that the controller experienced a “general loss of situational awareness”, having failed to scan the area, but adds that the Cessna pilot contributed to the incident with “poor decision-making” by not maintaining the standard traffic pattern.