What happened
On March 6, 2011, at approximately 16:50, an ultralight vehicle, a Quicksilver GT400, was performing a recreational flight near Tainan. The pilot departed from a non-designated airfield known as Feilong Airfield in the Annan District, flying toward the Zengwen River at an altitude between 300 and 400 feet. After circling the river, the pilot transitioned to a northwest heading.
During the flight, the pilot noticed a significant drop in engine RPM and a loss of power. Despite attempts to adjust the throttle, the engine's output continued to decline. With the altitude dropping to approximately 100 feet, the pilot was forced to execute an emergency landing in a soft-soil agricultural field approximately 7.5 kilometers from the departure point. The impact caused the pilot to strike the control column, resulting in minor injuries to the left cheek. The aircraft sustained substantial damage, including a bent longitudinal spar and damage to the landing gear.
The investigation
The investigation examined the wreckage and interviewed the pilot. The aircraft was powered by a Rotax 503 two-stroke engine, which is not a certified aircraft engine. The investigation found that while the pilot believed the engine had completely stopped before impact, the propeller damage indicated that the engine was still producing some power at the time of the landing, though insufficient to maintain flight.
Evidence showed that the engine failure was not caused by fuel exhaustion, as residual fuel was found in the carburetor and fuel was still leaking from the lines at the scene. The investigation also noted that the aircraft lacked a valid airworthiness certificate and had no documented maintenance history. Furthermore, the aircraft's engine was over 20 years old, and the pilot was operating without a valid ultralight vehicle pilot certificate. The flight took place in an unauthorized airfield and airspace.
Findings
- The primary cause of the accident was the loss of engine power, which prevented the pilot from maintaining flight.
- The engine used, a Rotax 503, is an uncertified engine designed for experimental use, which is subject to sudden stoppage and does not meet standard aircraft durability requirements.
- The pilot lacked the necessary training and certification for this specific type of ultralight vehicle and was unfamiliar with its performance limits, such as stall speeds.
- The choice of landing site, characterized by soft soil, contributed to the substantial damage sustained by the airframe during the forced landing.
- The operation was conducted in an unauthorized airspace and from an unapproved airfield.