Incident Overview
On October 14, 2013, at approximately 11:01 JST, a serious air proximity incident occurred near the temporary helipad adjacent to Kumamoto Airport in Kumamoto Prefecture, Japan. The two aircraft involved were a Eurocopter AS365N3 (registration JA15KM) operated by the Kumamoto Prefecture Disaster Prevention Fire Fighting Aviation Unit, and a privately owned Robinson R44 II (registration JA344T).
Flight Histories
The Helicopter-A (JA15KM) was hovering at 60 ft (about 18 m) above ground level near the temporary helipad, conducting rescue training with four persons on board, under the control of the ground controller.
The Helicopter-B (JA344T) had arrived at Kumamoto Airport earlier for a familiarization flight. It requested and received approval from the Tower controller for a straight-out departure, then took off from runway 07 at about 11:00. The intended destination was a temporary helipad approximately 5 nm east of the airport. The captain of Helicopter-B, believing it prudent to vacate the runway early, turned right immediately after takeoff without communicating this intention to the Tower. This turn directed the helicopter toward the hovering Helicopter-A.
The captain of Helicopter-A saw Helicopter-B soon after takeoff and felt danger as it turned and approached at low altitude, but he did not take evasive action, believing the other helicopter would fly overhead. The vertical distance at closest proximity was reported by the Helicopter-A captain as 15 m, while the Helicopter-B captain estimated it as more than 200 ft (about 61 m) based on eye measurement. Neither pilot took evasive action.
Air Traffic Control Actions
The Tower controller visually observed Helicopter-B deviating to the south (right) soon after takeoff but did not query the pilot or provide traffic information about Helicopter-A. The controller cited four reasons: (1) the straight-out departure instruction implied the aircraft should follow the runway extension; (2) the hovering altitude of Helicopter-A was lower than nearby buildings, so the controller believed landing and departing aircraft would not come close; (3) at the time, the Tower was controlling three other aircraft; (4) past experience with long transmissions from Helicopter-B raised concerns about communication interference.
Meteorological Information
At 11:00 JST, the weather at Kumamoto Airport reported wind direction 220° at 5 kt, prevailing visibility 30 km, sky clear (SKC), temperature 25°C, dew point 13°C, and altimeter setting 30.08 inHg.
Additional Information
The report notes that the flight procedure for straight-out departure under visual flight rules is not specified in the Japanese Air Traffic Service Procedure Handbook, ICAO SARPS, or PANS-ATM. The Aeronautical Information Manual Japan (AIM-J) describes that when breaking from a traffic pattern, pilots may continue straight-out or exit with a 45-degree turn. The Helicopter-B captain believed that a range within 15 degrees left or right of the runway centerline at takeoff start was permissible. The Japan Civil Aviation Bureau commented that air traffic control generally recognizes that aircraft do not make turns soon after takeoff for straight-out departures, with no distinction between fixed-wing and rotorcraft.
Investigation Conclusion
The Japan Transport Safety Board designated the event as a serious incident. No probable cause was stated in the report.