What happened
On 30 November 2018, a Cessna 310-R, registration EC-EQK, was conducting a local training flight at Cuatro Vientos Airport to familiarize a pilot with the aircraft's handling. During a touch-and-go maneuver, the pilot attempted to retract the landing gear after reaching an altitude of 700 feet. Approximately 25 seconds after initiating the retraction, the crew heard a loud mechanical noise and detected the smell of smoke.
Using an onboard mirror, the crew observed that the nose landing gear leg had failed to lock in the retracted position. The crew attempted to operate the gear both electrically and via the manual emergency extension procedure, but the mechanism remained immobile. After declaring an emergency, the pilot performed a landing at Cuable Vientos Airport using only the main landing gear. The impact caused the propellers and the underside of the fuselage to sustain significant damage.
The investigation
The investigation focused on the failure of the nose gear extension and retraction system. Upon disassembly of the front landing gear leg, investigators identified a broken drive tube. Laboratory analysis at the Universidad Politécnica de Madrid confirmed that the tube suffered a complete fracture of a lug due to an instantaneous ductile overload. There were no signs of fatigue or corrosion on the component.
Testing of the electric landing gear motor revealed that while it functioned correctly in the downward direction, it failed to rotate in the upward direction. The investigation determined that the motor's operating time was exceeded during the incident, likely causing the burning odor noted by the crew. The investigation also reviewed the aircraft's maintenance records, noting that recent inspections and airworthiness directives had been properly implemented.
Findings
- The primary cause of the accident was a broken component within the nose gear extension and retraction mechanism, which prevented the gear from being fully extended.
- The fracture of the drive tube was caused by an instantaneous longitudinal overload, likely resulting from a misalignment of the tubes within the extension and retraction system during the attempt to retract the gear.
- This misalignment also caused the electric landing gear motor to exceed its intended duty cycle, leading to its failure in the upward direction.