What happened
On March 13, 2015, a Gulfstream Aerospace G-IV, registered JA001G, was conducting a flight inspection near Niigata Airport when it was struck by lightning. The aircraft, operated by the Civil Aviation Bureau of the Ministry of $Land, Infrastructure, Transport and Tourism$, was flying under Instrument Flight Rules (IFR) on a mission to verify the performance of aeronautical navigation facilities.
While performing a descending turn at an altitude of approximately 6,500 ft, the crew encountered scattered thin clouds. At roughly 14:35 JST, the crew experienced a loud noise through the radio equipment, followed seconds later by a bright flash and a physical impact accompanied by a popping sound.
Following the strike, the crew identified several abnormalities in the cockpit, including discoloration on various instrument displays and the failure of the captain's side airborne DME. Although the aircraft remained controllable, the crew elected to terminate the inspection and return to Tokyo International Airport. Upon landing, a post-flight inspection revealed significant damage to the left front fuselage outer skins, the front lower fuselage, and the left horizontal stabilizer, including lost static discharger components and burnt rivets.
The investigation
The Japan Transport Safety Board (JTSB) examined the flight history, meteorological data, and the physical damage to the airframe. Investigators analyzed weather radar images and lightning sensor data from a local provider, which had recorded a strike near the flight path at the time of the incident. The investigation also reviewed the aircraft's maintenance records and the flight data recorder, which showed no other operational abnormalities during the flight.
Findings
- The lightning strike likely occurred as the aircraft entered thin, electrically charged cumulus clouds that were difficult to predict or avoid.
- The weather conditions were characterized by a winter pressure pattern, which often produces widespread, low-altitude electrically charged clouds along the Sea of Japan coast.
- The physical damage—including skin punctures, burnt rivets, and the loss of a static discharger—is consistent with a lightning discharge path traveling from the front left fuselage to the left horizontal stabilizer.
- The failure of cockpit instruments was attributed to the proximity of the strike to the cockpit area.