"Engine Malfunction Due to Unnoticed Flaw in F-16 Resulted in Inflamed Crash Previously"
F-16 Engine 'Blind Spot' Linked to $21 Million Fighter Crash at Holloman Air Force Base
A problem in the F-16's F100-PW-220 engine, preventing maintainers from visually inspecting a critical component, was identified as the cause of an April 2024 crash that destroyed a $21 million F-16C fighter at Holloman Air Force Base, New Mexico, according to a new Air Force report.
The fighter lost thrust shortly after takeoff, and the pilot, a rated instructor, failed to restore power using established procedures, necessitating ejection. The pilot sustained only minor injuries upon landing near White Sands National Park.
The F-16 was part of a four-plane training formation. Seconds after takeoff, the pilot reported hearing a loud bang, feeling a loss of thrust, and experiencing violent shocks and engine vibrations. Witnesses on the ground and in the air reported seeing either fire or a strange, non-standard orange hue emanating from the rear of the jet.
When recovery procedures failed, the pilot ejected at an altitude of 1,460 feet, less than two minutes into the flight. The aircraft crashed into a sand dune and exploded, and the pilot was promptly recovered by an Army helicopter.
The investigation estimated total damages at $21.7 million.
Investigators found that in the engine's fifth stage, a small vane was turned about 25 degrees more open than adjacent vanes, causing abnormal aerodynamic forces that stress-fractured one of the fifth stage's blades, disrupting airflow, and leading to engine failure.
Investigators were unable to determine the cause of the vane's misalignment. The engine had experienced a foreign object damage (FOD) event in August 2022 that damaged the first stage of the inlet fan, but no damage was observed in stages 2-4 or 6-13.
Pratt & Whitney's analysis attributed the vane's misalignment to the FOD event. However, expert opinions varied on whether it was plausible for damage to occur to a later stage if no damage was observed in the preceding stages.
"A field-level engine maintainer with forty-three years of experience with F100 engines testified, 'it happens, it's kind of unexplainable, but it's frequent enough that we all have seen instances,' the report states. "A field-level engine and borescope instructor, however, had never seen this occur. An experienced depot maintainer said it could occur but was very rare. Finally, a depot aerospace engineer said it would be surprising if it occurred."
Investigators also examined the possibility of the vane's misalignment during depot-level maintenance but were told it was unlikely as such misalignments would cause the entire stage to bind and fail quality control checks.
"I find the cause for the turned vane impossible to determine," the AIB president concluded.
Inspectors noted that field maintainers would not have been able to detect the misaligned vane during visual inspections due to the absence of an access port allowing a fifth stage borescope inspection. The engine had last been in depot maintenance in 2016, nearing its next overhaul at the time of the accident.
Maintenance personnel did not send the engine to the depot after the FOD event because they could not find any damage to stages 2-4 or 6-13, and subsequent inspections revealed no issues with those stages. It is possible that stage 5 was damaged, but they could not verify as they would for other stages due to the engine's design.
The Report highlights the engine's lack of access for field-level maintainers as a known 'blind spot.' The F-16 program office in the Air Force Life Cycle Management Center has already conducted a risk assessment regarding whether engines should be sent to the depot for unscheduled maintenance if the surrounding stages show no signs of damage. The accident investigation board makes no mention of whether the program office is revisiting that assessment after the incident, and the AFLCMC spokesperson could not immediately provide comment from the program office.
Regarding the F100-PW-220 engine's challenges affecting maintenance and safety, two significant issues are worth noting. The engine's complexity requires specialized knowledge and tools for effective maintenance, and the need for advanced diagnostic capabilities and precise repair techniques can create challenges for maintenance teams. Additionally, depending on the location and availability of parts, maintenance can be delayed, impacting operational readiness.
- The crash of the F-16C fighter at Holloman Air Force Base was traced back to a problem in the F-16's F100-PW-220 engine, a known issue in the aerospace industry's general-news.
- The air force pilots must regularly deal with complex aircraft like the F-16, a situation that requires exceptional skills, a field faced with challenges in finance and maintenance, as illustrated by the $21 million crash incident.
- Despite the advancements in the sports of flying, the F-16 program still encounters issues related to engine maintenance and safety, such as the 'blind spot' that complicates visual inspections.
- The aerospace industry experiences issues related to foreign object damage (FOD), as demonstrated by the August 2022 FOD event on the F-16's engine, leading to unforeseen consequences down the line.
- The ongoing debate among experts on the possibility of FOD causing misalignment in later stages of the engine highlights the intricacies and uncertainties in the maintenance and repair processes within the aerospace industry.
