What happened
On August 31, 2003, a Piper PA-34-200T, registration EC-HYP, was conducting a dual-instruction flight at Cuatro Vientos Airport in Madrid. The aircraft was operated by Aerea Flying Training Organization and was carrying three occupants: an instructor, a commercial pilot in training, and another instructor.
After completing a series of training maneuvers, the aircraft returned to the airport for landing on runway 28. The landing was described by the crew as a normal, though somewhat firm, touchdown. During the landing roll, the aircraft' and the right wing began to dip progressively. As the speed decreased, the right landing gear strut failed, causing the right side of the aircraft to settle onto the runway.
The aircraft dragged along the pavement for approximately 500 meters, supported by the right wheel and the cabin step. The incident caused damage to the right landing gear, the right propeller blades, and various parts of the fuselage and wing. Although witnesses reported seeing fire beneath the aircraft due to sparks and fuel leakage from the right tank overflow, no fire actually ignited. All 3 occupants escaped the aircraft without injury.
The investigation
Investigators examined the right main landing gear and discovered that the trunnion (P/N 67926-15) had completely fractured, along with the internal shock absorber piston. Fractographic analysis revealed that the failure originated from a fatigue crack at the forging die closure zone. This crack progressed through a combination of fatigue and stress corrosion until it reached a critical size, resulting in a final static overload failure.
The investigation also reviewed the maintenance history of the aircraft. The aircraft had a total of 2,316 hours of flight time. While the left gear had been upgraded to an improved design, the right gear had not been replaced since the aircraft's manufacture in 1977. The last inspection of the right trunnion had been performed 51 flight hours prior to the accident.
Findings
- The primary cause of the incident was the structural failure of the right main landing gear trunnion due to pre-existing fatigue damage.
- The failure occurred during a moderately firm landing, which provided the necessary load to trigger the final rupture of the weakened component.
- The maintenance program followed the FAA Airworthiness Directive (AD 94-13-11) interval of 100 hours for inspections after 2,000 hours of service, rather than the more frequent 10-hour interval suggested in the Piper Service Bulletin (SB 787B).
- The use of the aircraft for flight training likely contributed to the fatigue, as training landings often involve higher structural loads than standard operations.