What happened
On January 26, 2018, a Cessna A188B, registration PT-WUX, was performing a ferry flight from the Arroio Grande Aerodrome to an agricultural landing area in the Sarandi District, Rio Grande do Sul. The flight was being operated by Aeroagrícola Sureña Ltda. for agricultural purposes.
Upon touching down at the destination, the aircraft experienced a sudden leftward yaw. The pilot attempted to correct the direction by applying maximum left-side braking; however, the pilot discovered that the right brake assembly was ineffective. This loss of directional control caused the aircraft to veer left off the landing strip, eventually colliding with a fence. The impact resulted in substantial damage to the landing gear, left wing, elevator, and lower cowling. The pilot was uninjured.
The investigation
CENIPA investigators examined the aircraft and found significant accumulation of dirt and grime across the engine, wings, and main landing gear. Specifically, the brake assemblies were found to be contaminated with a mixture of grease and soil.
Technical measurements revealed that the brake linings on the right main landing gear were severely worn. The thickness of the linings was measured at 1.85mm and 1.55mm, both of which fell below the manufacturer's minimum service limit of 2.38mm (3/32 inches).
Records indicated that the aircraft had undergone a 100-hour inspection only nine days prior to the accident, having flown just over eight hours since that maintenance event. Investigators concluded that the worn linings were likely not replaced during the recent inspection and that the contamination further reduced the friction necessary for effective braking.
Findings
- Excessive brake lining wear: The brake linings were below the minimum thickness required by the manufacturer's maintenance manual.
- Contamination: The presence of grease and soil on the brake components significantly reduced braking effectiveness.
- Maintenance oversight: The failure to replace worn components during a recent 100-hour inspection contributed to the accident.
- Inadequate management supervision: Both the maintenance organization and the aircraft operator failed to ensure the continued airworthiness of the aircraft.
Safety action
CENIPA issued the following recommendations:
- To the National Civil Aviation Agency (ANAC): To audit the maintenance organization (AERO STA Manutenção de Aeronaves Ltda.) to ensure they possess and apply the necessary resources and technical manuals required to service the Cessna A188B.
- To the operator (Aeroagrícola Sureña): To improve administrative and operational procedures for receiving and verifying maintenance services performed on their aircraft.