What happened
On February 1, 2003, at approximately 17:05 local time, a Cessna 172-RG, registration EC-ICY, was conducting a non-commercial pleasure flight from Jerez de la Frontera Airport toward Málaga Airport. The aircraft was carrying a pilot and three passengers. After approximately 25 minutes of flight at a cruise altitude of 5,500 feet, the pilot noticed vibrations in the aircraft's nose and observed the oil pressure dropping to zero. Shortly thereafter, the engine failed and could not be restarted in flight.
The pilot identified a suitable field near Jimena de la Frontera (Cádiz) and performed an emergency landing. The aircraft remained structurally intact, though the landing gear sank into the soft soil, causing damage to the landing gear, propeller, and engine. All four occupants were uninjured and were able to evacuate the aircraft on their own. A nearby helicopter from the Helimer Andalucía service, which happened to be in the area, located the occupants within 15 minutes and transported them to Jerez de la Frontera Airport.
The investigation
The investigation focused on the engine failure and the source of the oil loss. The pilot reported that the engine failure followed a period of vibration and a total loss of oil pressure. Upon inspection of the aircraft, investigators found that the engine had seized due to a lack of oil.
Evidence showed that oil was leaking from the bottom of the oil radiator, located on the right side of the aircraft. While the leak was difficult to see when the radiator was installed, it was visible once the component was removed. Investigators found that the oil had leaked from the radiator, flowed along the interior of the cowling, and exited through the cowling seals, heavily staining the right side of the aircraft with oil while the left side remained clean.
Laboratory testing of the radiator under standard operating conditions (75 psi and 175°F) revealed a leak rate of approximately 17 liters per hour. Given that the engine's maximum oil capacity is roughly 8 liters and approximately 2 liters remained in the system after the incident, it was estimated that the leak had been active for a maximum of about 20 minutes.
Findings
- The engine failure was caused by engine seizure resulting from oil depletion.
- A microscopic examination of the radiator revealed a small pore, likely caused by corrosion, surrounded by a 1-centimeter area of further corrosive damage.
- Because the leak was estimated to have occurred within a 20-minute window, it is unlikely that the leak could have been detected prior to the commencement of the flight.