Air Force loses $115 million gunship to a 'sideslip'

Story highlights

  • The four-engine gunship went inverted during a test flight
  • The plane did not crash, but the Air Force says it exceeded its load limits
  • The U.S. Air Force puts the loss at $115 million

(CNN)How can you destroy a $115 million airplane without crashing it?

Fly it upside down.
That's exactly what happened to one of the Air Force's newest gunships, the AC-130J Ghostrider, this year, according to a report from Air Force Materiel Command released this month.
    An AC-130J Ghostrider taxis to a runway at Eglin Air Force Base, Florida. (U.S. Air Force photo/Chrissy Cuttita)
    On April 21, the four-engine gunship was on a test flight over the Gulf of Mexico performing a "steady heading sideslip," according to an Air Force release. A "sideslip" is a maneuver in which the pilot slightly lowers a wing and applies opposite rudder to enable the plane to lose altitude fairly quickly. The maneuver is often used when planes are landing in a crosswind or when there is a need to lose altitude quickly. If you've seen those scary jetliner landing videos, the pilots are often executing a sideslip.
    "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," according to a statement from Air Force Materiel Command at Wright-Patterson Air Force Base in Ohio. The plane was flying at 15,000 feet when the mishap occurred. Recovery was at 10,000 feet, and it was flown safely back to Eglin Air Force Base in Florida. No one was injured.
    But because the plane flew upside down, it "over-G'd," or exceeded the load and stress limits on the airframe, meaning it can no long be considered airworthy, according to the Air Force report. It estimated the cost of the incident at more than $115 million.
    The service's Accident Investigation Board blamed the accident on the gunship pilot's "excessive rudder input during the test point followed by inadequate rudder input to initiate a timely recovery from high angle of sideslip due to overcontrolled/undercontrolled aircraft and wrong choice of action during an operation."
    The AC-130J Ghostrider is part of a long line of gunships on the C-130 platform that date back to the Vietnam War. The newest version began testing in 2014. They are expected to be operational by 2017, with a total of 32 in the Air Force's inventory by 2021.
    They will carry precision-guided munitions as well as 30 mm and 105 mm cannons, according to Air Force documents.