What happened
On 31 December 2018, an AEROSPOOL WT9 Dynamic/Speed, registration OM-DOC, was performing landing circuits at Hrade and Králové airport (LKHK) using VNAV approach. The aircraft, carrying two occupants, landed on the concrete surface of runway 15L in a standard configuration with flaps extended and the landing gear down and locked.
Following a smooth touchdown on the main landing gear at approximately 70 km/h, the aircraft continued straight along the runway. Shortly after the nose wheel made contact with the pavement, the front undercarriage leg began to shimmy violently. This intense vibration led to the structural failure and breakage of the nose gear strut. Consequently, the aircraft's nose collapsed, striking the runway surface. The impact caused significant damage to the aircraft's nose section, the landing gear fairings, and the exhaust system. The propeller also struck the runway, which resulted in the forced shutdown of the engine. There were no injuries to the crew or passengers, and no damage was caused to third-party property.
The investigation
The ÚZPLN investigation examined the aircraft's maintenance history, the pilot's qualifications, and the meteorological conditions at the time of the incident. The weather was reported as clear with minimal wind, and the runway surface was dry and clean. The investigation also included a specialized metallurgical analysis of the failed nose gear component conducted at the University of Chemistry and Technology in Prague.
Findings
- The pilot was fully qualified, medically fit, and experienced in operating this aircraft type.
- The aircraft had been maintained in accordance with the manufacturer's requirements and had shown no prior signs of mechanical abnormality.
- The primary cause of the incident was a material defect in the nose gear strut.
- Metallurgical testing revealed that the low-alloy chrome-molybdenum steel used in the strut web did not meet the minimum yield or tensile strength requirements specified by the relevant technical standards (EN 10216-4).
- The failure was likely due to improper heat treatment during the manufacturing process, which caused the material properties to degrade, eventually leading to the structural failure under operational loads.