What happened
On August 10, 2003, a Cessna 172J, registration EC-DAE, was performing a local flight departing from La Cerdanya Aerodrome (Girona) with one pilot and three passengers. During the taxi from the apron to the runway 07 threshold, the pilot noted a noise that disappeared while traversing a gentle slope. Following a normal takeoff and approach, the aircraft was in its landing roll after the flaps had been retracted.
During the rollout, the right main wheel locked, causing the aircraft to veer sharply to the right. The aircraft left the paved surface, traveled across the grass, and eventually struck an embankment located 6 meters from the runway edge. The pilot applied the left brake only after realizing the aircraft was exiting the runway. All four occupants (the pilot and three passengers) were able to exit the aircraft on their own and sustained no injuries, though the aircraft suffered substantial damage.
The investigation
The investigation focused on the mechanical state of the landing gear and the maintenance history of the aircraft. Upon inspection of the right main wheel assembly, investigators removed the aerodynamic fairing and the brake caliper. They discovered that the capscrew bolts used to secure the inner rim and the brake disc to the wheel hub had loosened and become deformed. Some bolts were found to be loose enough to be removed by hand, and two had fallen out during the disassembly of the brake caliper.
Further examination of the wheel hub revealed deformed and stripped threads. One bolt showed signs of being forced into its hole, with aluminum material from the hub threads embedded in the bolt. The investigation also reviewed the maintenance logs, noting that while the aircraft followed a progressive care program, the specific manipulation of these bolts typically only occurs during brake disc or tire changes. The last recorded 100-hour inspection, which included bearing lubrication, had not reported any issues with these bolts.
Findings
- The right main wheel locked during the landing roll, initiating the uncontrolled right turn.
- The capscrew bolts connecting the brake disc and the inner rim to the wheel hub had loosened due to vibration and improper installation/tightening.
- As the bolts loosened, they scraped the brake caliper support and damaged the anchor, leading to the mechanical lock of the wheel assembly.
- The exact timing of the bolt manipulation could not be determined, but it likely occurred after the last recorded 100-hour inspection.