Deep inside the Pratt & Whitney F100 engine used in F-16s, the fifth compressor stage was a place Air Force maintainers could not see without taking the engine apart. The Air Force Life Cycle Management Center’s propulsion directorate has now developed an inspection that reaches it, and F-16 technical orders require the check after every foreign object debris (FOD) event, Air & Space Forces Magazine reported Oct. 9, 2026.
The change follows two F-16 crashes that investigators traced to misaligned vanes in that stage. Both pilots ejected safely, but both jets were destroyed, and the magazine reported that “the total damages exceeded $54 million.”
The fix is laid out in Greg Hadley’s Oct. 9 report for Air & Space Forces Magazine, which is based on information from the Air Force. According to the report, “AFLCMC’s propulsion directorate developed the new process,” and it requires no engine modifications or new equipment. The magazine says the inspection “is meant specifically for Pratt & Whitney F100 engine models”; some F-16s fly with GE Aerospace F110 engines instead.
Why the fifth stage was a blind spot
Maintainers already had a way into most of the engine. “Maintainers can inspect many of the F100 engine’s stages using a borescope—a camera mounted on a flexible tube,” the magazine explains. “But the fourth and especially the fifth stages are hard to reach.”
Until now, according to the Air Force’s account in the report, it was “impossible for maintainers to inspect them without completely disassembling the engine,” work done only at depots.
The magazine describes the failure mechanism in general terms. A misaligned vane creates “abnormal aerodynamic forces” and “irregular wake patterns” that stress compressor blades in later stages. “That can lead to vanes or blades cracking or breaking, causing the entire engine to fail,” the report says.
The two crashes behind the change
The report identifies the two losses. “An F-16 crashed near Holloman Air Force Base, N.M., in April 2024,” and another jet, “belonging to the U.S. Air Force Thunderbirds, crashed in the California desert in December 2025.”
Subsequent investigations, the magazine says, determined that in both cases “the F-16s’ engines had failed because of misaligned vanes in the fifth stage.” Both engines had earlier FOD events on record, though, per the report, investigators could not conclusively tie those events to the misalignment. Task & Purpose summarized the findings the same way: Air Force investigators traced both failures to unrepaired damage inside the engine’s “blind spot,” and crews had recorded earlier FOD ingestion in both jets.
On-wing, and a redesigned part on order
Task & Purpose, reporting the same change on Oct. 8, 2026, quoted an AFLCMC spokesperson on how the check is done in practice: “The inspection can be done on-wing and is required after a FOD event occurs.” That means the engine stays in the jet for the look. The Task & Purpose report quotes the propulsion program office describing “a new borescope inspection procedure for the 4th and 5th stage vane arms,” and says a turned vane found during inspection still sends the engine to depot.
The inspection finds the problem; a second fix aims to make it rarer. An AFLCMC spokesperson told Air & Space Forces Magazine:
“Additionally, the program office has worked with Pratt & Whitney to redesign the vane arm to be more impact resistant. The new design is qualified, on order, and will be installed via forced retrofit as soon as available.”
The spokesperson’s statement gives no date for the retrofit. For now, the record is a new required inspection after every FOD event on F100-powered F-16s, and a redesigned vane arm that the Air Force says is qualified and on order.
Top image: A Pratt & Whitney F100 turbofan on a test stand at Robins Air Force Base, Georgia. Image Credit: Sue Sapp / U.S. Air Force — Public domain / Wikimedia Commons