Incident Overview
On Saturday, November 11, 2017, at approximately 16:24 Japan Standard Time, a privately owned Robinson R44 II helicopter (registration JA274J) and a Eurocopter EC135P2+ helicopter (registration JA831H) operated by Academic Corporate Body HIRATAGAKUEN came into close proximity over Akashi City, Hyogo Prefecture. The pilot of the Robinson R44 recognized a risk of collision and initiated evasive action. No injuries or damage to either aircraft were reported.
Flight History
The Robinson R44 (Aircraft A) departed from Yao Airport at 15:58, flying under Visual Flight Rules (VFR) with only the pilot in command onboard, bound for Taishi Temporary Helipad. The Eurocopter EC135 (Aircraft B) took off from Hyogo Prefectural Kakogawa Medical Center Temporary Helipad at 16:22 in response to an emergency medical service request, also under VFR. It carried a pilot in command, a mechanic serving as an outside watch, and two medical experts.
According to the near collision report submitted by the R44 pilot, the incident occurred during level flight at an altitude between 1,000 and 1,100 ft, magnetic heading 290°, speed 90 kt. The pilot initially sighted the EC135 in the forward right direction at a horizontal distance of 5–10 km and 200 ft below. After briefly looking ahead to maintain lookout, the pilot looked again and saw the EC135 approaching from a 45° angle below, closing to a horizontal distance of 30–60 m and a vertical separation of 100–200 ft. The R44 pilot reduced speed and executed a right turn climb to avoid a collision. At that moment, the EC135 appeared to make a rapid right turn and descend below the R44.
The EC135 pilot stated that after takeoff, the aircraft climbed to 1,200 ft while turning right, then began a gradual descent toward its destination. The mechanic, watching outside, spotted an unidentified object diagonally forward left and advised the pilot, saying "Above on the left." By the time the EC135 pilot looked up, the R44 was already passing just above and left. The EC135 pilot did not recognize a collision risk and continued descending without taking evasive action. The EC135 was at an altitude of 1,000 ft or less at the closest point.
Meteorological Information
Weather observations from the Akashi Automated Weather Station, located about 1.4 km southwest of the incident site, recorded at 16:20 and 16:30:
- 16:20: Precipitation 0 mm, temperature 14.6°C, wind from northwest at 5.4 m/s (gusting to 9.3 m/s), sunshine duration 0 minutes.
- 16:30: Precipitation 0 mm, temperature 14.5°C, wind from northwest at 6.8 m/s (gusting to 10.4 m/s), sunshine duration 0 minutes.
Sunset was at 16:58. The R44 pilot reported flight visibility of about 10 km and no sun glare due to cloud cover near the western horizon.
Aircraft Information
Aircraft A (Robinson R44 II) had a maximum takeoff weight of 1,134 kg, single-engine piston land. Its transponder was activated. Navigation lights, anti-collision lights (red strobe on tail boom), and landing lights were on. It was equipped with a VHF radio monitoring the Osaka Flight Service Center frequency.
Aircraft B (Eurocopter EC135P2+) had a maximum takeoff weight of 2,950 kg, multi-engine turbine land. Its transponder was activated. Navigation lights (green/red on horizontal stabilizer, white flashing on vertical stabilizer), anti-collision lights (white strobe on fuselage sides), and landing lights were on. It was equipped with two VHF radios monitoring intercommunication and company frequencies.
Investigation Details
The Japan Transport Safety Board (JTSB) investigated this serious incident following a Near Collision Report submitted on November 15, 2017. Radar tracking records were analyzed to estimate the positions and altitudes of both aircraft. No probable cause was determined in the investigation report.