What happened
On July 31, 2000, a DEA Yuma ultralight aircraft, registration CS-UJS, was conducting a VFR flight from Tavira to a private airstrip in Foral, São Bartolomeu de Messines. During the flight, the pilot observed a significant rise in engine oil temperature, increasing from 110°C to 125°C, accompanied by a drop in oil pressure from 4 bar to 2 bar.
Fearing a potential engine failure, the pilot decided to perform a precautionary emergency landing. The pilot selected a wooded agricultural valley for the landing, utilizing the aircraft's STOL capabilities. While the approach and touchdown were initially normal, the nose wheel struck a depression in the terrain, causing the nose gear to deform and forcing the aircraft to veer right. As the aircraft continued across the uneven ground, the right main landing gear collapsed due to the failure of the attachment bolts. The aircraft then struck trees, causing structural damage to the right wing, aileron, and horizontal stabilizer.
Both the pilot and the passenger escaped the aircraft without injury.
The investigation
The GPIAAF investigation focused on the mechanical state of the engine and the circumstances of the landing. Investigators examined the engine compartment and found that an additional cooling shroud/plate, intended to regulate airflow to the engine, had become detached. This loose component was obstructing the air intake, which directly caused the engine to overheat.
Furthermore, the investigation reviewed the aircraft's maintenance history and the pilot's pre-flight procedures. It was noted that the pilot could not confirm that a full pre-flight inspection had been performed. The investigation also found that the maintenance records for the Rotax 912S engine were inconsistent with the manufacturer's recommended maintenance program.
Findings
- The primary cause of the engine overheating was an obstructing cooling plate that had become loose and blocked the air intake.
- The landing gear failure and subsequent structural damage were caused by the aircraft striking uneven terrain during the emergency landing.
- Maintenance of the CS-UJS was found to be deficient and not in accordance with the manufacturer's requirements.
- The pilot's pre-flight inspection may have been insufficient to detect the loose cooling component.
- The pilot demonstrated limited knowledge of local Portuguese aeronautical regulations, specifically regarding airspace restrictions near Faro.