What happened
On May 20, 2005, a PIPER PA-28 181 ARCHER II, registration EC-DKB, was performing traffic circuits around runway 13 at the Axarquía Aerodrome (LEAX) in Málaga. The aircraft was being operated by Real Aeroclub de Málaga for flight instruction, carrying an instructor and a student pilot.
During the sixth circuit, while in the right downwind leg, the crew heard impacts beneath the left wing and observed that the left main landing gear leg had detached. The gear remained suspended only by the brake hose. The crew immediately verified the functionality of the flaps, ailerons, and elevators, finding all flight controls operational. Ground observers confirmed that the left gear leg had completely separated from the airframe.
The instructor took control of the aircraft and, after evaluating the situation, decided to land at the local Axarquía Aerodrome rather than diverting to Málaga Airport. The landing was executed by touching down first with the right wheel, followed by the nose wheel, and finally the damaged left side. The aircraft traveled approximately 5 meters after contact. Although the impact of the strut caused a small puncture in the wing skin behind the fuel tank, no fire occurred. Both the instructor and the student pilot were uninjured and evacuated the aircraft on foot.
The investigation
Investigators examined the structural failure of the left main gear leg, specifically focusing on the breakage of the trunnion cylinder lug where it attaches to the gear leg via a bolt. The investigation also included a follow-up discovery made nine months later, when a crack was detected in the same component on the right main gear leg.
Laboratory analysis of the fractured left leg and the cracked right leg revealed no metallurgical defects, corrosion, or evidence of fatigue. Microfractographic examination indicated that the fracture surfaces in both instances were consistent with a progressive static overload phenomenon. The study found no evidence of abnormal loading from unintended sources or improper maintenance, noting that a 100-hour inspection had been completed just nine days prior to the accident with no deficiencies noted in the landing gear.
Findings
- The structural failure of the left main landing gear was caused by the application of successive static overloads.
- These overloads likely occurred during multiple hard landings associated with the aircraft's use in flight training.
- The magnitude of these loads was estimated to be between the limit load and ultimate load, causing material deformations that weakened the component without exceeding design limits.
- The discovery of a crack in the right gear leg's trunnion lug, mirroring the failure of the left, supports the conclusion of cumulative structural degradation from heavy landings.