What happened
During a scheduled training exercise with the United States Navy, a Lear Jet was operating in formation with a second aircraft. While flying at 15,000 feet, the wingman aircraft noticed that the flaps on the lead aircraft were partially extended. After the pilot acknowledged the observation, the wingman saw the flaps retract and noticed smoke or gas emitting from the left rear section of the aircraft. The pilot of the lead aircraft subsequently reported a cabin odor.
Shortly after, the wing andman observed red fluid dripping from the tail cone, followed by visible flames emerging from the aft equipment bay access door. The pilot declared an emergency and expressed intentions to divert to a nearby island airfield. The wingman moved to the lead position to assist. As the aircraft descended through 7,000 feet, radio contact was lost. ADS-B tracking indicated the aircraft performed several descending turns before the signal ceased. The wreckage was later discovered underwater, approximately 4 miles northwest of the final tracking point. The debris field was highly fragmented, and recovery efforts retrieved roughly 40 percent of the aircraft.
Findings
Post-accident examination of the wreckage revealed extensive fire and smoke damage spanning from the center wing fuselage through the wing roots and the empennage. Investigators identified damage to the aft equipment bay bulkhead consistent with a focused heat source, such as a fire caused by a leak in a pressurized hydraulic or fuel line. Evidence of fire damage was also found in the left engine pylon, which contained engine fire detection circuits.
Analysis of the hydraulic shutoff valves showed the left valve was closed, suggesting the crew likely attempted to shut down the left engine following a fire indication. While the cause of the observed flap movement remained undetermined, investigators focused on the fuel and hydraulic systems. A critical finding involved the left fuel motive flow line; while the outboard side of the fuselage fitting was intact, the inboard side inside the aft equipment bay was missing an aluminum b-nut and the connecting line. The fire likely originated near this fitting, where a leak from the pressurized fuel motive flow line would have fueled an uncontrollable fire, ultimately leading to the loss of aircraft control.