What happened
On August 22, 2009, a Stemme S10-VT motoplaner, registration PR-DOQ, was performing a flight from Fazenda Belluno to the Aeroclube de Santa Catarina. During the approach, the pilot shut down the engine to proceed in a gliding configuration. Upon entering the traffic pattern, the pilot deployed the landing gear and observed green indicator lights.
However, due to intense sunlight reflecting off the aircraft's acrylic canopy, the pilot misperceived the status of the gear. While the pilot believed both gear legs were locked down, a pilot on the ground observed that the left landing gear remained retracted. Upon being alerted to this via radio, the pilot, realizing there was insufficient altitude to restart the engine for an emergency extension, opted to land on the grassy area adjacent to the runway to avoid obstructing the main asphalt strip.
During the landing roll on the grass, the aircraft's left wing touched the ground. As the speed decreased, the aircraft entered a ground loop, causing the right landing gear strut to twist and break. The impact also damaged the nose gear, the propeller tip, and the underside of the left wing.
The investigation
CENIPA investigators examined the aircraft's maintenance records and the cockpit environment. The investigation focused on why the left gear failed to extend and why the pilot did not detect the error. While a loose wire was noted in the landing gear compartment, investigators could not definitively confirm if this caused the malfunction. A visual inspection by a qualified mechanic found the locking mechanism to be operating normally. The investigation also considered the impact of environmental conditions, specifically the sun's glare, on the pilot's ability to monitor the cockpit indicators accurately.