What happened
On January 13, 2024, an X-AIR HAWK ultralight aircraft, registered as U-H77 and operated by BFA Flying Company Limited, departed from a temporary landing area in Nongprue, Banglamung district, Chonburi province. The pilot and one passenger were conducting a local visual flight rules (VFR) flight at approximately 800 feet. During the flight, the aircraft lost control and collided with a tree in a rice field near Huayyai Temple, approximately 5 kilometers south of the departure point. The impact resulted in the complete destruction of the aircraft. The pilot died from severe trauma, while the passenger sustained serious injuries and was transported to Bangkok Hospital Pattaya.
The investigation
The Aircraft Accident Investigation Committee (AAIC) examined the wreckage and maintenance records. Inspections revealed that the engine and flight controls were functioning normally prior to the impact. However, the wing surface fabric, made of Dacron Polyester, had significantly deteriorated due to age and weathering after more than eight years in service. The aircraft's leading edges had been repaired using Polyvinylchloride (PVC) tape, which was found detached and unable to adhere firmly to the degraded original fabric. This PVC debris became entangled with the left horizontal stabilizer cable. Additionally, the Dacron Polyester on the vertical stabilizer was torn open.
Findings
The investigation established that the loss of aircraft control was caused by the failure of the wing surface materials. The deteriorated Dacron Polyester and the improperly attached PVC repairs led to a loss of lift and aerodynamic imbalance between the wings. The detached PVC further disrupted control surfaces by catching on stabilizer cables, causing abnormal directional control. Contributing factors included the aircraft's failure to undergo required inspections of wing control surfaces and empennage fabrics at 900 hours or five years as specified in the maintenance manual, and the use of non-compliant PVC materials for repairs without proper documentation.
Safety action
The AAIC issued safety recommendations to the Civil Aviation Authority of Thailand (CAAT) and aviation associations. These include stricter supervision of aircraft maintenance to ensure adherence to manufacturer manuals, particularly regarding wing fabric inspections and material selection. Recommendations also emphasized the mandatory recording of all maintenance activities in the Aircraft Logbook and the requirement for personnel performing such inspections to possess specialized knowledge and expertise appropriate for the aircraft type.