What happened
On 9 April 2022, a Diamond DA-40, registration EC-IQD, was performing a training flight at Cuatro Vientos Airport in Madrid. The flight, operated by Aerotec Escuela de Pilotos, involved an instructor and a student pilot. After completing a local VFR training mission and landing without incident, the crew taxied the aircraft toward the general apron via gate E.
While maneuvering to avoid a sharp turn due to the aircraft's wingspan, the front landing gear leg suddenly collapsed. The impact caused the aircraft to slide forward on its nose, resulting in significant damage to the propeller blades and the engine. Both the instructor and the student pilot were unharmed during the event.
The investigation
Investigators examined the wreckage and the aircraft's maintenance history. The aircraft had undergone a 200-hour overhaul on 5 February 2022, which included a dye penetrant inspection of the nose wheel fork pivot axle as required by EASA airworthiness directive AD 2009-0016. No signs of fatigue were detected at that time. A subsequent 100-hour inspection had been performed on 30 March 2022, which also revealed no anomalies.
Laboratory analysis of the fractured components identified a fatigue fracture in the upper part of the pivot axle. The investigation found that a geometric notch at a non-smooth transition between sections acted as a point of stress accumulation. Furthermore, heavy wear on the chrome plating suggested significant friction between the axle and the fork, contributing to the failure.
Findings
- The primary cause of the accident was an in-service material fatigue failure of the pivot axle on the nose wheel fork.
- The design of the pivot axle was inadequate due to an abrupt transition in section that created a stress concentration point.
- There was an inconsistency between Diamond's Maintenance Manual and its Service Bulletins regarding the required inspection methods and intervals.
- While the operator had complied with existing airworthiness directives, a newer service bulletin (MSB 40-091) had increased inspection frequency to every 100 hours without being formally incorporated into the Maintenance Manual or supported by a new airworthiness directive.