Incident Overview
On August 9, 2003, at approximately 12:45 Japan Standard Time, a serious incident involving a near collision occurred over the sea approximately 4 nautical miles south of Okinoerabu Island, Kagoshima Prefecture, Japan. The aircraft involved were a NAMC YS-11A, registered JA8781, operated by Japan Air Commuter as scheduled passenger flight 031, and a privately owned Cessna A185F, registered N185GW. Neither aircraft took evasive action. There were no injuries to the 70 persons aboard the YS-11A (65 passengers and 5 crew) or the 2 persons aboard the Cessna. Neither aircraft sustained damage.
Flight Histories
Japan Air Commuter Flight 031 (JA8781)
The YS-11A departed Kagoshima Airport at 11:08 JST under Instrument Flight Rules (IFR) en route to Yoron Airport. It cruised at 10,000 feet. At about 12:36, it began descending. After passing over Erabu NDB at approximately 6,500 feet at 12:42, it received approach clearance for Yoron Airport from Naha Area Control Center and continued descending toward 3,000 feet. At the time of the incident, the aircraft was at 4,300 feet MSL, on a magnetic heading of 219°, with a true airspeed of 230 knots.
Cessna A185F (N185GW)
The Cessna departed Naha Airport at 11:48 JST under Visual Flight Rules (VFR), bound for Fukuoka Airport. It was cruising at 4,500 feet MSL. The pilot had established radio contact with Kagoshima Flight Service Center to obtain traffic information for Okierabu Airport. At around 12:43, the Cessna reported its position as approximately 15 nautical miles southwest of Erabu VORTAC at 4,500 feet. It was flying northeast, which under VFR required an odd-thousand-plus-500-foot altitude; 4,500 feet was appropriate.
Encounter Details
At about 12:45, as the YS-11A descended at 4,300 feet approximately 10 nautical miles southwest of Erabu VORTAC, it converged with the Cessna, which was level at 4,500 feet in the same vicinity. The YS-11A's Traffic and Collision Alert Device (TCAD) detected the Cessna and issued warnings. The crew of the YS-11A sighted the Cessna at around 11 o'clock, above their altitude. The closest proximity was estimated at 200 meters horizontally and 150 to 200 feet vertically, with the Cessna passing off the left side (9 o'clock). No avoidance action was taken by either aircraft. The YS-11A landed at Yoron Airport at 12:53. The Cessna landed at Fukuoka Airport at 16:52.
Crew Statements
The pilot-in-command of the YS-11A stated that after the TCAD alert, he reduced airspeed and searched visually but initially could not see the other aircraft due to haze. When sighted, he judged the separation sufficient and did not take action. The first officer similarly observed the other aircraft and did not consider avoidance necessary. Both noted haze conditions and that the horizon and Yoron Island were not visible.
Investigation
The Aircraft and Railway Accidents Investigation Commission (ARAIC) investigated the incident, reviewing digital flight data recorder recordings, air traffic control radar data, and interviewing crews. The pilot of the Cessna did not submit a near collision report.
Conclusion (Probable Cause)
No probable cause is stated in the report.