Investigators have concluded that a $22 million US Air Force F-16 fighter jet crashed near Joint Base Andrews, Maryland earlier this year because its engine was improperly assembled and was missing key parts, the service announced Thursday.
The crash occurred April 5 during a routine surface attack training mission.
Shortly after departing Joint Base Andrews, the aircraft "experienced an uncommanded engine acceleration, followed by a loss of thrust," forcing the pilot to execute "critical action procedures for low altitude engine failure," according to an Air Force press release.
The pilot was able to safely eject and did not sustain any injuries but the aircraft was destroyed as it hit the ground.
Large portions of the aircraft, including a wing and the fuselage, were found intact after the crash, allowing investigators to identify it as an F-16, police said at the time of the incident.
An investigation into the mishap revealed evidence that "the main engine control was missing a required 600-degree training ring and the anti-rotation pin," according to the Air Force.
"The misassembled differential pressure pilot valve caused the main engine control to incorrectly meter abnormally high fuel flow to the engine," the service said. "This led to severe engine overspeed, severe engine over-temperature, engine fire, and, ultimately, a catastrophic engine failure."
The pilot was able to extinguish the fire but not before the engine sustained considerable damage that rendered it unusable.
"Because the distance to the nearest suitable recovery airfield was beyond the aircraft glide capabilities, the pilot directed the aircraft toward a nearby open field prior to ejecting," the Air Force said.
The jet ultimately crashed in a wooded area.
The Air Force is treating the mishap as an isolated incident, according to spokesperson Maj. Malinda Singleton.
According to the investigation report, the engine was improperly assembled due to procedural failures on the part of the Commodities Maintenance Squadron at the Air Logistics Complex in Oklahoma City, Oklahoma.
The engine component was sent to Tinker Air Force Base to be overhauled by the squadron.
But the maintenance group was faulted in the report for having inadequate procedures for keeping track of spare parts which was described as a "substantially contributing factor" in the crash.
The group completed a full end-to-end process audit on the F-16 Main Engine Control production line following the crash in April, Air Force spokesperson Jerry Bryza told CNN.
"Process improvement measures were taken and additional quality checks throughout the assembly and test portions of the overhaul process were added to include two-step visual verification that 100% of required replacement items had been installed during overhaul," he said.
Despite the error, investigators found that the engine did ultimately pass standard testing procedures before it was sent back to Joint Base Andrews and reinstalled into the aircraft.
Both the pilot and aircraft involved in the incident are assigned to the 113th Air National Guard Wing at Andrews. The report did not find evidence faulting the 113th's maintenance personnel.
Known as the "Capital Guardians," the 113th Fighter Wing is charged with defending the nation's Capital and also provides fighter, airlift and support forces capable of local, national and global employment, according to the Air Force.
Lockheed Martin's F-16 Fighting Falcon is a multi-role aircraft, built to carry out a variety of missions. The US Air Force currently has just over 1,000 F-16s in its inventory.
