What happened
On August 27, 2017, a Robinson R44 helicopter, registered JA7981, operated by Takumi Enterprise Helicopter & Airplane Co., Ltd., performed an emergency landing at a school ground in Fushimi Ward, Kyoto City. The incident occurred at approximately 17:05 JST while the aircraft was cruising at an altitude of roughly 5,300 feet, about 28 km northeast of Otsu City, Shiga Prefecture.
The flight originated from the Oyabe Helipad. On the preceding day, the aircraft had participated in various flight activities, including refueling at the Uchiondo Helipad. During that refueling process, the pilot noted the fuel gauge needle moved but did not visually verify the fuel levels by opening the caps. Following further flights on the morning of the incident, the helicopter was not refueled again.
Although the pilot's flight plan specified a departure with 110 liters of fuel, the aircraft actually departed with a much lower quantity. During the flight toward Kyoto, the pilot maintained high power settings for climbing and cruising, which increased the fuel consumption rate. As the aircraft approached the southwest of Lake Biwa, the "LOW FUEL" warning light illuminated. Realizing that the remaining fuel was insufficient to reach the intended destination, the pilot executed a precautionary landing at a nearby open area. There were no injuries and no damage to the aircraft.
The investigation
The Japan Transport Safety Board (JTSB) examined the flight history, GPS records, and the aircraft's fuel system. Investigators analyzed the fuel consumption rates based on the aircraft's power output, wind conditions, and altitude. The investigation also reviewed the pilot's pre-flight procedures and the company's operational oversight.
Measurements taken after the incident revealed that the actual fuel remaining in the system at the time of the warning light was approximately 18.6 liters. By calculating the fuel consumed during the flight and the amount refueled on the ground, investigators determined that the aircraft had likely departed the Oyabe Helipad with only about 87 to 91 liters of fuel, far below the 110 liters stated in the flight plan.
Findings
- The pilot failed to accurately verify the actual fuel quantity on board before departure, relying on an inaccurate assumption of fuel levels following previous flights.
- The flight plan was inaccurate, as the aircraft did not carry the amount of fuel reported to the Civil Aviation Bureau.
- The pilot did not continuously monitor the fuel gauges during the flight, failing to notice that the consumption rate was higher than expected due to high power settings and changing wind conditions.
- The pilot did not adhere to safety notices recommending landing before the fuel gauge reaches one-quarter full, which could have allowed for a more controlled diversion earlier in the flight.