What happened
On July 1, 2003, a Boeing Stearman 1B75A, registration ZS-LZZ, was involved in a ground accident at Pilanesberg Airport. The aircraft was conducting a private flight, departing from Rustenburg with an intended landing at Pilanesberg.
Prior to departure, the pilot noted intermittent stiffness in the left wheel during taxiing. Although the aircraft was moved manually from the hangar without issue, the pilot found it necessary to apply significant brake pressure to keep the plane stationary during the pre-takeoff power check. During the takeoff roll, the pilot felt intermittent resistance, but the aircraft reached takeoff speed normally, and the flight proceeded.
Upon touchdown on runway 0 and5, the left wheel suddenly locked. This caused the aircraft to veer sharply to the left, leading to a ground loop that ended with the aircraft resting on its nose at the side of the runway. There were no injuries and no fatalities resulting from the event.
The investigation
SACAA AIID investigators examined the mechanical state of the aircraft and its maintenance history. The aircraft's last Mandatory Periodic Inspection (MPI) had been completed on May 25, 2002, with approximately 31 hours of flight time logged since that inspection. Records indicated that the pilot had performed 66 landings between December 18, 2002, and the date of the accident.
Findings
- The investigation identified a malfunctioning brake master cylinder as the primary factor.
- The master cylinder failed to release applied brake pressure back into the system.
- This failure caused the drum brake shoes to remain in an activated position, leading to the sudden wheel lock during the landing roll.