What happened
On the evening of 29 October 2019, an F-16C (T/N 90-0755) departed Holloman Air Force Base, New Mexico, as part of a three-aircraft flight for a routine night training mission. The mission was intended to maintain instructor pilot proficiency in low-altitude navigation using night vision goggles.
Approximately 40 minutes into the flight, while operating in the number three position of a trail formation, the aircraft experienced a catastrophic engine failure. This failure triggered an uncontrollable engine fire at a low altitude. The pilot successfully ejected from the aircraft and was later recovered by a US Army helicopter from Fort Bliss, Texas. The aircraft crashed on private land approximately 95 miles southeast of Holloman AFB, resulting in the total destruction of the airframe.
The investigation
The investigation focused on the mechanical failure of the engine and traced the origin of the malfunction back to depot-level maintenance performed at Tinker AFB, Oklahoma, in September 2016. Investigators examined the overhaul process of the engine’s Inlet Fan Module (IFM) and reviewed maintenance logs and personnel qualifications.
Review of the work cards revealed that during the assembly of the IFM, a critical component—the 1st Stage Rear Air Seal—was not installed. The investigation established that the error occurred when a trainee continued assembly past the point where the missing seal could be visually verified. Furthermore, investigators found that the required inspections and sign-offs by both the trainer and the certified inspector were performed a day after the work was actually completed, at which point the 2nd Stage Stator Case had already obscured the area where the seal should have been located.
Findings
- The primary cause of the mishap was the failure to install the 1st Stage Rear Air Seal during the engine overhaul.
- The absence of this seal allowed the 2nd Stage Fan Blades to migrate forward under operational strain, leading to their liberation.
- This mechanical failure caused a significant loss of thrust and an uncontained engine fire after the departing blades perforated an A-1 fuel tank.
- Contributing factors included the use of unqualified and untrained maintenance personnel performing critical tasks.
- A lack of direct supervision allowed the trainee to proceed with assembly without real-time verification.
- Negligent procedural practices were identified, specifically regarding maintenance personnel signing off on completed steps without performing the actual physical inspections.