What happened
On April 21, 2007, a Pierre Robin DR400/180R, registration CS-DCN, was performing an aerial work flight involving glider towing at the Évora Municipal Aerodrome. After a successful glider release, the pilot returned to the aerodrome to land on runway 01. During the approach, the pilot transitioned from the base leg to the final leg, during which the carburetor heat was turned off.
Approximately 800 meters from the runway threshold and at an altitude of 300 feet AGL, the pilot reduced power. At this moment, the engine began to vibrate and subsequently failed, with white smoke visible from the engine cowling. The pilot continued the descent on the glide slope, but the aircraft was unable to reach the runway surface. At 14:15 UTC, the aircraft struck a wire fence surrounding the aerodrome. The impact caused the aircraft to stop 7.5 meters past the collision point, with the nose resting on the ground. The pilot sustained minor injuries, while the aircraft suffered extensive damage to the engine, propeller, landing gear, wings, and cockpit structure.
The investigation
The GPIAA investigation examined the engine performance, meteorological conditions, and the pilot's adherence to procedures. Investigators performed a fuel analysis, which ruled out water contamination as a cause for the engine failure. A post-accident test of the engine on a test bench showed it was functioning perfectly, and the blue discoloration found in the air filter was determined to be fuel spill from the impact rather than evidence of engine flooding. The investigation also reviewed the accuracy of aerodrome information, noting several discrepancies in NOTAMs and landing charts regarding the exact location and height of the perimeter fences, though these were not considered contributing factors.
Findings
- The primary cause of the accident was an engine failure likely caused by carburetor icing.
- A significant contributing factor was the pilot's failure to follow the landing checklist, specifically neglecting to ensure the carburetor heat was fully ON and locked during the approach.
- Atmospheric conditions, including the temperature and dew point, were highly conducive to the formation of carburetor ice at the aircraft's operating altitude.
- The pilot was well-familiarized with the aerodrome and the location of the obstacles.