What happened
On September 17, 2024, a pilot and a passenger operated a Challenger II Special ultralight aircraft with registration U-B23 for sightseeing flights from Pai Airport in Mae Hong Son Province. The aircraft departed from runway 19 at approximately 11:00 a.m. for a second flight of the day. During the final approach, the aircraft encountered a gust of wind from the left side of the runway. This crosswind caused the aircraft to deviate to the right of the centerline.
The left main landing gear touched down on the runway surface, while the right main landing gear contacted the grassy area beyond the right edge of the runway approximately 360 meters from the threshold. The aircraft continued moving across the grass for about 60 meters before coming to a stop in a ditch located 425 meters from the runway threshold and 18 meters to the right of the runway edge. The aircraft sustained minor damage, including deformation of the nose landing gear support structure and fracture of the aluminum control linkage structure. Both the pilot and the passenger were uninjured and exited the aircraft unaided.
The investigation
The Aircraft Accident Investigation Committee for the Aircraft Accident and Incident Investigation Commission Thailand investigated the incident. Key findings included:
- The pilot held a valid Private Pilot Licence for Ultralight aircraft with appropriate ratings and a valid medical certificate.
- The pilot had approximately 20 hours of flight time on the Challenger II Special type, with 13 hours 45 minutes in the last 90 days.
- The aircraft had a valid Certificate of Airworthiness and Registration. Inspections revealed no mechanical failures in the flight control system, brake system, or engine (Rotax 582).
- Weather conditions were normal with visibility over 10 km and occasional gusty winds. No official weather report was available for Pai Airport at the time.
- CCTV footage and eyewitness statements from airport personnel confirmed that a gust of wind from the left caused the aircraft to deviate right during approach.
Findings
The primary cause of this serious incident was a gust of wind from the left affecting the aircraft during touchdown, which resulted in the pilot being unable to maintain directional control and keep the aircraft on the runway. A contributing factor was the pilot's potential lack of detailed study of the Owners Manual and insufficient skill to control the aircraft in gusty crosswind conditions, given their limited experience (approximately 20 hours) on the Challenger II Special type.
Safety action
The Civil Aviation Authority of Thailand (CAAT) was recommended to:
- Conduct random checks and close oversight of private ultralight pilots regarding competency, particularly for approaches and landings in crosswind conditions.
- Ensure pilots strictly study and follow the Owners Manual, focusing on techniques for gusty crosswind conditions.
The Mae Hong Son Aviation Club was also advised to remind pilots to study the Owners Manual with emphasis on crosswind landing techniques.