An Air Self-Defense Force chief inspector said Wednesday his team found a glitch in an electric circuit that might have inadvertently caused an ASDF F-4 fighter jet's 20mm cannon to fire into a civilian area in Hokkaido during an air-to-ground firing drill Monday. During testing, the jet's 20mm cannon started operating without the trigger being pulled as an ASDF accident investigator shook the control stick with the armaments function turned on, said ASDF Maj. Gen. Yoshishige Hori, the inspector general.
They determined that an electric signal was sent to fire the cannon whenever the control stick was moved to a certain point, he said, adding that investigators have not yet determined how it was sent. Hori added that he has not yet determined if the malfunction affects just the one fighter or the whole F-4 inventory. Nationwide, there are 85 F-4 EJ Kai deployed, including the one involved in the accidental firing.
Hori said he had never imagined that a cannon could automatically fire just by moving the control stick.