Air Force Thunderbird crashed after failure in engine 'blind spot'

One of the Air Force’s most talented pilots was looping his F-16CM Thunderbird jet into a routine maneuver during a training flight last December that required him to push the plane’s engine to full thrust, which pilots call “Military Power.”

Anticipating the familiar feeling of being pushed into his seat by the full power of the F-16’s engine, the pilot later told Air Force officials that he suddenly felt “like the jet just…stopped midair.”

Deep inside the F-16’s Pratt & Whitney F100 engine, two fan blades had broken loose, causing “catastrophic engine damage and a significant loss of thrust.” A camera mounted on the F-16 captured the moment of failure as an explosion of fire from the plane’s engine.

A rear-facing video camera onboard an Air Force Thunderbird F-16 captured the moment the plane’s engine suffered a catastrophic failure, leading to a crash minutes later. Air Force photo.

The pilot was not just a member of the elite Thunderbirds, but was one of two pilots on the team experienced and trusted enough to be chosen as a “solo” performer at the team’s airshows, and for the next four minutes he fought to keep the dying jet in the air, according to an accident report on the mishap released Monday. He swooped lower to keep his speed up, flew down a valley to avoid higher terrain, and, running through emergency checklists, managed to restart the engine.

But it offered no thrust and four minutes after he’d felt the plane “stop” in midair, and just 400 feet above the ground, he announced on the team’s radio: “ejecting.”

The plane crashed four seconds later in a fireball captured by a camera on a second Thunderbird following close behind. The pilot landed safely under a parachute and waved to a Thunderbird wingman who buzzed overhead. The $33 million jet was completely destroyed.

A final report of an Aircraft Investigation Board’s review of the Thunderbird crash released Monday cleared the plane’s pilot, the mechanics who worked on the plane, and the Thunderbird leaders who oversee safety of the demonstration squadron and who approved the flight from any blame in the mishap.

“Before the flight, [Thunderbird] personnel performed all required inspections, documentation, and servicing,” wrote Col. J.C. Brooks, the board’s president. “The pilot was current, qualified, medically fit, and performed appropriate actions. The scheduled mission was supervised correctly and released by pertinent authorities.

Instead, Brooks said, the plane had been brought down by two engine fan blades that broke free in a spot so far inside the engine that maintainers never inspect them, even with advanced tools during major inspections. “The cause of the mishap was three misaligned, or turned, variable vanes in the 4th and 5th stages of the MA engine’s compressor section,” Brooks wrote. “One 5th stage compressor blade and one 6th stage compressor blade failed due to high cycle fatigue and separated during flight, causing catastrophic engine damage and a significant loss of thrust, thereby making sustained flight impossible.”

The Thunderbird crash was the second time in less than two years that similar failures of fan blades in an F-16’s Pratt & Whitney F100 engine were found to have caused an F-16 to crash. An F-16 at Holloman Air Force Base, New Mexico, crashed in April 2024 after a fan blade in the same spot inside its engine also broke free, causing catastrophic damage that left the jet’s pilot with no option but to eject.

At the center of both crashes is a unique section on the F-16’s engine that the report on the 2024 Holloman crash called a “blind spot.” When operating, the Pratt & Whitney F100 produces thrust by heating and accelerating air through 13 fans, or stages, pushing super-heated exhaust out of the plane’s rear to power it forward. Each stage is made up of hundreds of steel fan blades and vanes, which operate under extreme temperatures and forces.

Missing fan blades from the 5th (left) and 6th (right) stages of the Thunderbird F-16's engine. Investigators determined the blades broke off during flight, causing damage in the engine that left the plane unflyable. — Missing fan blades from the 5th (left) and 6th (right) stages of the Thunderbird F-16’s engine. Investigators determined the blades broke off during flight, causing damage in the engine that left the plane unflyable. Air Force photo.

According to both of the accident reports, Air Force maintenance crews have little trouble inspecting and repairing the first four stages at the front of the plane. Crews can also check the 7th through 13th stages from the rear of the plane or by using special scope cameras inserted through access ports, or “APs,” along the engine.

“These APs provide limited borescope views of the 2nd, 3rd, 4th, 7th, 8th, 12th, and 13th stages of engine compression, as well as the combustion chamber,” the report found.

But Stages 5 and 6 are inaccessible to mechanics during routine maintenance checks, and “no APs exist which enable comprehensive inspection of the 5th and 6th stages of the engine core module,” the report said.

Those two stages, investigators said, can only be checked during major overhauls, when the entire engine is removed from the plane.

Fan blades in Stage 5 failed in both the Holloman F-16 and the Thunderbird jet, Investigators who examined the wreckage found. A blade in the 6th stage also failed on the Thunderbird plane. In each case, investigators ruled that mechanics followed correct maintenance procedures but had no chance to spot the flaws.

Neither investigation was able to determine when the damage within the hidden sections initially occurred.