What happened
On May 26, 2014, a CSA Sportcruiser, registration HB-WYC, was performing a training flight at the Lommis airfield (LSZT) in Switzerland. The flight was part of a training program for a student pilot, accompanied by a flight instructor. After completing several successful circuits, the crew performed a final approach without the use of landing flaps.
During the landing, the aircraft touched down approximately 150 meters past the runway threshold. Shortly after the main gear made contact, the nose gear collapsed. The impact caused the aircraft's nose to strike the grass runway, and the propeller came to a halt. The deceleration was significant enough to dislodge the crew's headsets and goggles. There were no injuries to the occupants, though the aircraft sustained light damage and minor damage occurred to the airfield surface.
The investigation
SUST examined the aircraft's maintenance history and the mechanical state of the landing gear. The investigation revealed that the nose gear had been replaced in 2012 with a modified version. While the aircraft had undergone a 100-hour inspection in April 2014, which included checks for cracks as prescribed by the manufacturer's service bulletin, the specific fatigue cracks in the steering axis were not detected.
Investigators also analyzed flight data from the aircraft's electronic flight instrument system (EFIS). The data showed that the approach speed was approximately 67 KIAS at 5 and 50 feet above the ground, which was higher than the 60 KIAS recommended in the pilot operating handbook.
Findings
Technical analysis established that the accident was caused by the failure of the already damaged nose gear steering axis during the landing sequence. Several contributing factors led to the pre-existing damage:
- An inadequate design of the nose landing gear assembly.
- Approaches conducted at excessive speeds.
- Frequent operations on grass runways, which contributed to the development of fatigue cracks.
Safety action
Following the accident, the manufacturer updated its service bulletins to include more rigorous inspections of the pivot and fork. Additionally, the manufacturer recommended replacing the older nose gear assembly with an improved version (P/N SG0300N) designed for better fatigue resistance, particularly for aircraft used in intensive flight training or operating from unpaved surfaces. EASA subsequently issued airworthiness directives to mandate these inspections and replacements.