What happened
On June 10, 2008, a Cessna 170A, registration PT-AQO, crashed during takeoff from Estância Santa Rita (SSKG) in Campo Grande, Mato Grosso do Sul. While climbing at approximately 10 meters, the aircraft began drifting to the left. The pilot attempted to correct the deviation by applying right rudder and right aileron input; however, the aircraft responded by banking even more sharply to the left. The aircraft subsequently struck a wall adjacent to the dirt runway, causing severe damage to the airframe and the loss of the engine. The pilot survived the impact without injury.
The investigation
CENIPA's investigation determined that the accident was caused by an inadvertent reversal of the aileron control cables during a recent 50-hour inspection. Although the inspection did not require intervention in the aileron controls, the mechanic disconnected the cables to address a report of stiff controls. During reconnection, the cables were installed in an inverted manner.
Investigators found that the error went undetected through multiple layers of defense: the mechanic failed to notice the incorrect movement, the maintenance supervisor failed to identify the discrepancy during quality oversight, and the pilot failed to detect the reversal during pre-flight control checks. The investigation noted that the error was particularly difficult to detect because, from a ground-based visual perspective, the movement of the ailerons appeared to correspond correctly with the movement of the control stick, even though the aerodynamic effect was reversed.
Findings
- Maintenance error: The mechanic connected the aileron control cables in an inverted configuration.
- Human error (Lapses): The mechanic, the supervisor, and the pilot all committed active errors (lapses) due to a lack of attention to the specific direction of control response.
- Judgment: The pilot failed to identify the control discrepancy during pre-flight inspections.
- Design vulnerability: The aileron control cables were designed in a way that made them interchangeable, allowing for the incorrect installation.
- Supervision: The quality supervisor failed to detect the maintenance error.