Incident Summary
On December 21, 2019, at about 11:21 JST, a privately owned Beechcraft A36 (registration JA3815, designated Aircraft A) and a Spring Airlines Airbus A320-214 (registration B-9940, designated Aircraft B) approached each other closely about 1.1 nm west-southwest of Saga Airport. The Airbus A320, operating as scheduled Flight 8577, took evasive action in response to a Traffic Alert and Collision Avoidance System (TCAS) resolution advisory (RA). The incident was later classified as a serious incident by the Japan Transport Safety Board (JTSB).
Flight Histories
Aircraft A departed Yao Airport at about 08:58 with a captain and three passengers, en route to Fukue Airport under visual flight rules (VFR). It maintained level flight at 4,500 ft and was manually controlled. At about 11:03, the pilot contacted Fukuoka Flight Service Center (FSC) and reported its position 37 nm east of Saga Airport. Aircraft A had only one VHF radio and remained tuned to the Fukuoka FSC frequency from around 11:03 onward.
Aircraft B departed Shanghai Pudong International Airport with 159 people on board (including 7 crew and 152 passengers) and was flying under instrument flight rules (IFR) at 6,000 ft on a direct route from Nagasaki VOR/DME to Saga VOR/DME. At about 11:19:16, it contacted Fukuoka Departure for transfer of communication control. Fukuoka Departure observed a VFR aircraft on radar at 4,600 ft, 4 nm east of SGE, and provided this traffic information to Aircraft B.
Air Traffic Control Communication
At about 11:19:47, Fukuoka Terminal Control Area (TCA) estimated the VFR aircraft was Aircraft A and attempted to contact it on the TCA frequency, but received no response because Aircraft A was tuned to Fukuoka FSC. Fukuoka TCA then inquired with Saga Radio about the VFR aircraft, but Saga Radio had no information. At 11:20:04, Fukuoka Departure instructed Aircraft B to descend to 5,000 ft and cleared it for an ILS approach to Runway 29. At 11:20:19, after the VFR radar target disappeared, Fukuoka Departure told Aircraft B that the VFR aircraft was likely 3 nm east of SGE and instructed it to contact Saga Radio. At 11:20:45, upon contacting Saga Radio, the flight information officer there recognized the VFR aircraft via an Aircraft Position Display Unit (APDU) and informed Aircraft B of an unidentified aircraft at display altitude 4,600 ft near SGE.
Evasive Action
At 11:21:13, the TCAS on Aircraft B issued a Traffic Advisory (TA) at altitude 5,310 ft, 2.5 nm west-southwest of SGE. Aircraft B reported to Saga Radio that it was visually searching for the unidentified aircraft. At 11:21:25, Saga Radio broadcast traffic information to all aircraft that an Airbus A320 was descending to 5,000 ft about 2 to 3 nm west of Saga Airport. As Aircraft B approached 5,000 ft with the autopilot set to level off, at 11:21:29 the TCAS issued an RA instructing a climb at 5,070 ft. The flight crew disengaged the autopilot and executed the RA. At about 11:21:42, Aircraft B reported to Saga Radio that it had taken evasive action and climbed to 5,200 ft.
At approximately 11:21:46, the two aircraft reached their closest point, about 1.1 nm apart west-southwest of Saga Airport. Aircraft A was at 4,540 ft and Aircraft B at 5,190 ft, with a horizontal separation of 0 nm. The captain of Aircraft A observed the other aircraft approaching head-on, climbing, and passing immediately above, but took no evasive action. After the RA was cleared, Aircraft B descended again at 11:21:54 and commenced the ILS approach.
Aftermath
On February 21, 2020, the captain of Aircraft A submitted a Near Collision Report to the Ministry of Land, Infrastructure, Transport and Tourism. The JTSB investigated and classified the event as a serious incident.