What happened
On August 26, 2010, a PIPER PA-3/4-200T, registration EC-EJV, was performing a positioning flight from Tenerife Norte to El Berriel for an airworthiness certificate renewal. The aircraft, operated by Aerotec, was occupied by the pilot, a flight instructor, and a maintenance technician.
Upon landing on runway 25, the pilot attempted to decelerate but discovered that the left main brake was non-functional. Despite attempts by the pilot and the co-pilot to pump the brakes to restore hydraulic pressure, the aircraft could only brake using the right main wheel. This asymmetrical braking caused the aircraft to deviate from the runway centerline. During the excursion, the right main tire burst, and the aircraft struck a depression on taxiway B. The impact caused the right main gear and the nose gear to collapse, leading the propellers to strike the ground as the fuselage slid along the asphalt. There were no fatalities and no injuries among the three occupants.
The investigation
The CIAIAC investigation focused on the hydraulic failure and the maintenance history of the braking system. Investigators found that the left brake assembly was leaking hydraulic fluid due to the deterioration of the piston O-rings. The O-rings were found to be deformed and squared rather than circular, indicating they had been subjected to excessive temperatures.
Further inspection revealed that the brake assembly was incorrectly configured. While the aircraft was equipped with a 30-83 brake package, the pistons installed were from a 30-65 package. Crucially, the thermal insulator required for the 30-83 assembly was missing, replaced by a manually fabricated metal piece. This lack of insulation allowed heat to reach the O-rings, compromising their seal.
Findings
- The primary cause of the accident was a failure in the left brake assembly resulting from an incorrect configuration of the braking components.
- The failure was driven by the use of incorrect O-rings and the absence of necessary thermal insulation, which led to overheating and loss of hydraulic pressure.
- A contributing factor was the high approach speed, as the crew had failed to extend the flaps during landing.
- Maintenance records showed that the left brake had experienced three similar hydraulic leaks in the ten months preceding the accident, yet no investigation into these repetitive failures was conducted as required by the maintenance organization's manual.
- There was no effective mechanism or documentation within the CAMO to track the specific configuration of components installed on different aircraft in the fleet.