What happened
On October 8, 2021, a Diamond DV 20, registration EC-JRH, was conducting a dual-instruction flight training session consisting of takeoffs and landings at Sabadell Airport. The flight was operated by Aero Link Air Services.
During the third landing of the session, the student pilot initiated the flare too high and at an insufficient airspeed, resulting in a sudden drop of the aircraft onto the runway. Although the instructor noted the maneuver, the impact was not immediately identified as a hard landing, and no immediate aircraft anomalies were detected. Consequently, the training session continued.
During the fifth and final landing of the session, as the aircraft decelerated on the runway, the nose wheel began to sink. The instructor initially believed the tire had punctured, but soon realized the steering control was lost due to a structural failure. The aircraft came to a halt on the runway approximately 10 meters from taxiway C. Both the instructor and the student pilot were uninjured.
The investigation
The investigation focused on two primary elements: the unstabilized approach and the structural failure of the nose gear.
Technical analysis of the nose gear fork revealed that the failure occurred through a ductile tearing mechanism caused by an overstress event that exceeded the material's strength. Metallographic, chemical, and tensile tests confirmed that the aluminum alloy (EN-AW 6082 T651) met all specifications. No evidence of fatigue, corrosion, or pre-existing material defects was found, indicating the component was in good condition prior to the impact.
Regarding the flight maneuvers, the investigation examined the instructor's decision to continue the session following the third landing. It was noted that while the student's approach was unstable, the instructor did not initiate a go-around (motor and al aire) to correct the situation.
Findings
- The primary cause of the accident was an unstabilized approach that resulted in a hard landing, generating forces that exceeded the structural limits of the nose gear fork.
- The instructor did not identify the third landing as a hard landing and allowed the training session to proceed.
- The nose gear fork failed due to an overstress event; no prior fatigue or corrosion contributed to the breakage.
- The operator's standard operating procedures (SOPs) regarding stabilized approaches lacked specific, measurable criteria.