What happened
On December 21, 2019, a privately owned Beechcraft A36, registered JA3815, was conducting a level flight under Visual Flight Rules (VFR) toward Fukue Airport. Simultaneously, an Airbus A3 320-214, registered B-9940, operated by Spring Airlines Co., Ltd., was descending toward Saga Airport on a scheduled flight from Shanghai.
As the two aircraft approached each other near Saga Airport, the airliner was following instructions from Fukuoka Departure to descend to 5,000 feet. At approximately 11:21 JST, the Traffic Collision Avoidance System (TCAS) on the Airbus A320-214 issued a Traffic Advisory (TA), followed shortly by a Resolution Advisory (RA) instructing the crew to climb. The crew of B-9940 disengaged the autopilot and executed the climb to avoid a potential conflict. At the point of closest proximity, the aircraft were approximately 1.1 nm apart with an altitude separation of roughly 650 feet. The pilot of the Beechcraft A36 observed the other aircraft passing nearby but did not initiate any evasive maneuvers.
The investigation
The Japan Transport Safety Board (JTSB) investigated the incident, examining radar tracking, ATC communications, and the Quick Access Recorder (QAR) from the airliner. The investigation focused on why the VFR aircraft was unable to receive traffic information and why the flight paths converged. Investigators reviewed the communication logs from Fukuoka Departure, Fukuoka Flight Service Center, and Saga Radio to determine the flow of traffic information between the various ATC facilities.
Findings
- The Beechcraft A36 was unable to receive critical traffic updates because its single VHF radio was tuned to the Fukuoka Flight Service Center frequency, which did not provide radar traffic information via the aircraft's position display.
- The pilot of the Beechcraft A36 failed to receive broadcasts from Saga Radio, as the aircraft was not monitoring that specific frequency.
- The Airbus A320-214 was aware of the potential conflict due to both ATC traffic information and its onboard TCAS.
- The pilot of the VFR aircraft approached the airliner without predicting its existence because the aircraft did not obtain necessary traffic information from ATC facilities.
- Despite the proximity, the JTSB determined there was no risk of collision as the vertical separation remained at approximately 650 feet at the closest point.