What happened
On May 31, 2008, at 11:20 UTC, a TL 2000 Sting ultralight aircraft, registration CS-UPS, was performing a dual instruction flight at Cascais Aerodrome. The flight consisted of standard circuits. During the final phase of the third landing on runway 35, the nose gear strut failed while the aircraft was at a low speed. This failure caused the propeller and the engine radiator to make contact with the asphalt. The aircraft subsequently slid approximately 40 meters along the runway before coming to a halt. The two crew members, an instructor and a student, were uninjured.
The investigation
The investigation examined the structural integrity of the nose gear and the operational history of the aircraft. The CS-UPS had accumulated 490 flight hours and approximately 1,400 landings. At the time of the incident, the aircraft's weight was calculated at 435 kg, which was within its maximum takeoff mass (MTOM) of 450 kg. The investigators reviewed the maintenance records and the manufacturer's guidelines regarding inspection intervals for nose gear components, specifically noting the increased stress placed on landing gear during flight training operations.
Findings
- The nose gear strut failed due to material fatigue in the upper structure of the gear leg.
- The failure was caused by the accumulation of structural loads from previous landings.
- The aircraft was being used for flight instruction, an operation that inherently increases the stress on the landing gear due to student pilot experience levels and frequent landings.
- While the crew did not report any recent hard landings, the cumulative effect of landing loads led to the structural rupture.
Safety action
Following the incident, the operator decided to accelerate the inspection schedule for the nose gear, moving the inspection interval to every 500 landings. The operator also implemented more rigorous checks for cracks or fissures during periodic inspections.