What happened
On May 28, 2023, a Cessna U206G, registration OB-1247, was performing a passenger transport flight from Yurimaguas to the Bellavista landing strip in the Loreto region of Peru. The flight, operated by Aero Palcazu S.A.C., carried one pilot and five passengers.
Upon landing on the unpaved runway, the pilot noted a significant loss of braking effectiveness as the brake pedal traveled to the floor. Although the pilot attempted to pump the brakes to recover partial pressure, the aircraft could not be stopped within the runway limits. As the aircraft approached the end of the strip, the pilot faced an imminent risk of overrunning into an adjacent embankment. To avoid this, the pilot executed a maneuver to steer the aircraft toward the left side of the runway. During this turn, the inertia caused the right wing to strike the ground, resulting in significant damage to the wing surface. The aircraft eventually came to a stop within the runway area, and all five passengers were evacuated without injury.
The investigation
The investigation conducted by the CIAA focused on the sudden failure of the braking system. Technical analysis of the aircraft revealed a hydraulic fluid leak originating from the left main landing gear brake line (Line Assy-Brakep/n 1280506-145).
Metallurgical and fractographic examinations performed by a specialized laboratory determined that the brake line had developed cracks due to material fatigue. This fatigue was driven by pitting corrosion that began on the external surface of the pipe and propagated inward. The investigation found that the corrosion was caused by the degradation of the anti-corrosive coating, leaving the metal vulnerable to the highly corrosive, humid tropical environment in which the aircraft operates.
Findings
- The primary cause of the accident was the loss of braking effectiveness due to a hydraulic fluid leak caused by a cracked brake line.
- The crack was the result of material fatigue associated with pitting corrosion.
- The corrosion was triggered by the deterioration of the protective anti-corrosive coating and exposure to a highly corrosive environment.
- The aircraft was operating in a tropical region characterized by extreme humidity, which accelerated the degradation of the component.
- There was no evidence that the specific inspections recommended by the manufacturer for aircraft operating in tropical or highly corrosive environments were being performed on the hydraulic brake lines.