What happened
On December 8, 2016, an Embraer EMB-810D, registration PT-VSM, was performing a local test flight at the Aeródromo Nacional de Aviação (SWNV) in Goiânia, Brazil. The flight was intended to verify the functionality of the autopilot system following an annual maintenance inspection.
After approximately 45 minutes of flight, the pilot initiated the landing sequence. During the landing roll, approximately 700 meters after touchdown, the landing gear warning horn activated, and the left main landing gear began to retract. This caused the aircraft to lose directional control and veer to the left, eventually exiting the paved runway and entering the adjacent grassy area. The aircraft sustained light damage, and the pilot was unharmed.
The investigation
CENIPA investigators examined the aircraft's hydraulic and electrical systems using jacks to simulate flight conditions. Testing confirmed that the landing gear deployment and retraction cycles functioned correctly, and all green indication lights for the gear being down and locked were operational. The landing gear locks were found to be intact, with no signs of breakage or wear.
Investigators also analyzed the runway markings. They noted that there were no propeller strike marks on the paved runway surface; the propeller only made contact with the ground once the aircraft had transitioned onto the uneven, grassy terrain beside the runway. This led investigators to conclude that the gear was properly locked at the moment of touchdown.
Findings
- The most probable cause of the incident was the unintentional unlocking of the left main landing gear caused by the elastic forces exerted on the gear leg and its lock due to the irregular terrain of the runway shoulder.
- The aircraft's left propeller struck the ground only after the aircraft left the paved surface.
- The pilot was properly licensed and medically certified for the operation.
- The aircraft was airworthy and within weight and balance limits.
- The contributing factors regarding specific control inputs and airport infrastructure remained undetermined.