Flight History
On March 13, 2015, a Gulfstream Aerospace G-IV registered as JA001G, operated by the Civil Aviation Bureau of the Ministry of Land, Infrastructure, Transport and Tourism, departed Obihiro Airport at 11:16 Japan Standard Time under Instrument Flight Rules. The aircraft carried a captain and four crew members for a flight inspection mission. During pre-departure weather checks, the crew noted that conditions along the planned route did not indicate a high likelihood of lightning or significant weather.
Flying south-southwest on Airway V31 at 9,000 ft, the pilots observed lower cloud layers but confirmed no cloud on the route toward Niigata Airport. At approximately 14:32, the aircraft began a descending turn above Niigata Airport for inspection of the next airway. While monitoring the weather radar display, the crew saw a precipitation area not on their route. They encountered scattered thin cloud, which they judged not to be thick cloud associated with turbulence or thunder.
At around 14:35, while passing through thin cloud at an altitude of about 6,500 ft, a very loud noise was heard on the radio equipment. After three to four seconds, the captain and first officer experienced an impact with a loud popping noise and a strong flash from the front of the aircraft. They continued the flight and checked instruments, finding discoloration on some cockpit displays and a loss of the captain-side DME display. The first officer's DME display remained functional and the discolored displays were still readable, so they concluded no serious flight abnormality existed.
After discussion, the crew decided to suspend the inspection and return to Tokyo International Airport due to inability to confirm airframe damage in flight. The aircraft landed at 15:26 without landing abnormalities.
Damage and Injuries
Post-flight inspection revealed substantial damage to the aircraft. The outer skin of the left front lower fuselage was damaged, requiring major repair in some areas. Approximately 20 rivets on that section were discolored or burnt. The No. 1 DME antenna on the front lower fuselage was partially damaged. On the left horizontal stabilizer, the tip of a static discharger was lost, the trailing edge was damaged, and outer skins near the discharger mounting surface showed discoloration and damage. Cockpit displays affected included the captain-side airborne DME display (became defective), the electronic flight instrument display (partially discolored), the first officer-side navigation instrument frequency display (defect), and the right engine fuel flow indicator display (defect). No injuries were reported among the five occupants.
Meteorological Conditions
At 14:00, Niigata Airport reported wind 300° at 11 kt, visibility 10 km or more, light showers, cloud layers with cumulus bases at 1,000 ft, 1,500 ft, and 2,500 ft, temperature 6°C, dew point 3°C. At 14:37, conditions included light thunderstorm, cumulonimbus cloud base 2,500 ft (amount 2/8), and lightning and thunderstorm observed 10 km southeast moving eastward. A winter pressure pattern with lingering cold air aloft was present; gale and lightning advisories were issued. The terminal aerodrome forecast indicated possible lightning near Niigata Airport. A lightning information provider recorded a strike at 14:34:20 about 5 km south of the estimated lightning strike location.