The incident occurred on April 21, 2015, while the United States Air Force was conducting a test flight over the Gulf of Mexico in a mammoth $115-million-dollar AC-130J Ghostrider gunship. The pilot attempted a maneuver called a “sideslip” which calls for applying opposite rudder while tilting the airplane right or left in order to lower a wing. The movement, which is often employed when planes are landing in a crosswind, is used to quickly reduce altitude. In this instance, the pilot tilted the aircraft too far and the huge plane inverted – and began flying upside down.
The plane was flying at 15,000 feet when the mishap occurred causing the plane to lose 5,000 feet of altitude before recovering at a dangerously low 10,000 feet. According to the Air Force report:
“The aircraft exceeded the targeted angle of sideslip until it departed controlled flight and momentarily inverted before being recovered after losing approximately 5,000 feet of altitude.”
The plane was able to safely fly back to Elgin Air Force Base in Florida but because the plane flew upside down, it “over-G’d”, or exceeded the load and stress limits on the airframe. This means the airplane is no longer airworthy and will likely never be flown again (unless tens of millions of dollars are spent to rebuild it).
The AC-130 Spectre/Spooky/Ghostrider/Stringer II line of planes are long-endurance ground-attack aircraft which have been in service as far back as the Vietnam War. The planes have a wingspan of approximately 133 Feet or about the length of half-a-football field. They weren’t meant to be flown upside down.