What happened
On January 6, 2018, at approximately 15:30, a self-built, uncertified ultralight aircraft performed an emergency landing on a beach near the Taiwan Highway 11 in Chenggong, Taitung. The aircraft, which was a custom design featuring a ROTAX 912 ULS engine, was being operated by two experienced pilots.
The flight began after the crew assembled the aircraft at a flood control road near Yuemei Bridge in Hualien. After waiting for weather conditions to improve, the crew took off at approximately 15:00, flying through the Hualien Mugua Creek and East Taiwan approved airspaces. While flying over Changbin, Taitung, the engine RPM suddenly dropped from 5,000 to between 3,500 and 3,800. Despite attempts to increase throttle, the engine power remained insufficient to maintain flight altitude.
As the aircraft continued to descend, the pilots sought an alternative landing site. Due to low cloud cover over the mountains, they directed the aircraft toward the coastline. Upon identifying an unobstructed beach, the pilots executed a landing maneuver involving a high-angle stall, causing the aircraft to strike the sand. The aircraft was destroyed upon impact, but both occupants exited the cockpit without injury.
The investigation
The investigation focused on the engine failure, the airworthiness of the aircraft, and the legality of the flight operations. Investigators examined the wreckage, which showed the tail section had separated from the fuselage due to the high-angle impact and the engine had detached from its mounting.
Technical examination of the ROTAX 912 ULS engine was severely limited because the impact and subsequent wave action had destroyed the fuel lines, carburetors, and electrical components. While the engine was still running during the descent and even briefly restarted at 300 feet, the exact cause of the RPM drop could not be determined due to the lack of flight data recorders and the destruction of the engine's internal components.
Furthermore, the investigation established that the aircraft was a private, uncertified build that lacked a valid inspection certificate from the Civil Aeronautics Administration (CAA). The flight also originated from an unauthorized takeoff site, classifying the operation as an illegal ultralight flight.