What happened
On March 30, 2024, an Evektor SportStar Max, registration JU-9088, was performing a training flight from Choibalsan to Ulaanbaatar. During the landing phase at Buyant Uhaa Airport, the aircraft experienced a high-angle, low-speed approach. Upon touchdown, the pilot applied forward elevator control, causing the aircraft to land with a nose-down attitude and a significant amount of vertical force.
As the aircraft decelerated on the runway, the nose landing gear collapsed. The aircraft then veered to the left, exiting the runway and traveling across the field. During the excursion, the propeller struck the concrete, and the right wingtip made contact with the ground. The aircraft eventually came to a stop at a 210-degree angle from its original heading. There were two persons on board, and no injuries were reported.
The investigation
The investigation examined the aircraft's mechanical condition, the pilot's training, and the maintenance history. Post-incident inspections revealed that the nose landing gear leg had collapsed toward the left due to structural failure at the mounting point. Investigators found evidence of improper maintenance, specifically that old grease had not been cleaned before new lubricant was applied, leading to significant wear and grooving on the suspension components.
Additionally, the investigation noted that the aircraft's wheel track was wider than the manufacturer's specifications. The investigation also reviewed the pilot's credentials, noting that while the pilot held a permit for ultra-light aircraft, they lacked a specific medical certificate and had not yet fully mastered advanced aerodynamic theory and flight manual procedures.
Findings
- The primary cause of the incident was a hard landing at a low airspeed, which placed excessive stress on the nose gear.
- The pilot's approach speed was likely near or below the stall speed (Vso), increasing the risk of a loss of control.
- The nose landing gear collapsed due to a failure in the mounting and suspension area, exacerbated by improper lubrication practices.
- The pilot's decision to use forward elevator control during touchdown contributed to the nose gear impact.
- The pilot was relatively new to the aircraft type and had not yet completed full training on weight and balance calculations or advanced aerodynamic theory.
- The aircraft's maintenance records for the engine were unavailable, and the club lacked sufficient qualified technical personnel.