History of Flight
On 21 March 2019 at 05:15Z, an instructor and a student pilot were conducting a training flight at Aeropark Zyn Kraal Aerodrome in Gauteng Province, South Africa. The student performed the pre-flight inspection and topped up the brake fluid. During start-up and power checks, no brake anomalies were noted. The take-off and training exercises proceeded without incident. After returning to the aerodrome, the instructor took control for the landing due to an unstable approach by the student. The touchdown was normal, but during the landing roll the instructor found that the brakes had failed entirely. Despite repeated attempts to pump the brakes, the aircraft did not decelerate. The instructor shut down the engine to reduce forward speed, but the aircraft overshot the runway and collided with the perimeter fence.
Injuries and Damage
Both occupants disembarked unassisted and reported no injuries. The aircraft sustained damage to the propeller blades. Other damage was limited to the perimeter fence.
Aircraft Information
The incident aircraft was a Tecnam P92 Echo, registration ZU-BJY, serial number 248. It was an amateur-built, single-engine, fixed tricycle landing gear aircraft. The total airframe hours at the time were 3304.7 hours. The last mandatory periodic inspection was conducted on 7 February 2019 at 3258.7 hours, 46 hours before the incident.
Brake System
The brake system consisted of hydraulically actuated disc brakes controlled by a lever between the seats. The master cylinder had a built-in fluid reservoir. A post-incident inspection revealed that the master cylinder O-ring seals were worn out, causing a loss of hydraulic pressure and brake failure.
Probable Cause
The investigation determined that the incident was caused by brake failure resulting from worn brake master cylinder O-rings. The O-ring failure was attributed to normal wear and tear.