History of the Flight
On 16 December 2002, a Cessna 152, registration CS-AYH, departed from Cascais Municipal Aerodrome at approximately 12:20 UTC on a positioning flight to Portimão. The flight was to return the aircraft to its home base after annual airframe inspection and engine overhaul. After passing Comporta, the pilot noticed an unusual odor in the cabin. Inspection of the instrument panel, light switches, and circuit breakers revealed no anomalies. Opening the wing root ventilation inlets did not dispel the odor. Looking outside, the pilot observed a smoke trail toward the tail and an oil stain on the leading edge of the left horizontal stabilizer. A more thorough check of the instrument panel showed a gradual decrease in engine oil pressure and a corresponding rise in oil temperature. The pilot, in contact with Lisbon Military Control (123.75 MHz), declared an emergency. The controller suggested using Sines aerodrome, which, although deactivated, was available for emergency landings. The pilot accepted and landed on runway 14 at approximately 13:30 UTC. The landing was normal; oil temperature remained within limits, though oil pressure had dropped below the minimum during the final two minutes of flight.
Injuries
No injuries occurred.
Aircraft Damage
The aircraft was not damaged.
Aircraft Information
The Cessna 152, serial number 1612, was manufactured by Reims Cessna in 1979. It was a high-wing, single-engine landplane with tricycle landing gear, powered by a Lycoming O-235-L2C engine (110 BHP). The aircraft had accumulated 8,702.4 hours total time. The most recent annual inspection was completed on 19 November 2002.
Meteorological Conditions
Weather was good across the area with light winds, scattered clouds above 5,000 feet, and horizontal visibility greater than 10 km. Weather was not a factor.
Communications
The pilot maintained continuous radio contact with Lisbon Military Control, which assisted in selecting and directing to a suitable diversion aerodrome.
Aerodrome Information
Sines aerodrome was listed in the AIP Portugal. Although closed to traffic, it accepted emergency landings by light aircraft. It had a gravel strip oriented 140°/320°, 1,150 m long by 40 m wide.
Tests and Research
After the precautionary landing, a technical team found an oil leak at the engine oil cooler body after refilling the system. The cooler was removed and replaced. Visual inspection showed numerous dents, distortions, and tears in the cooling fins. A leak test conducted by the investigation authority confirmed a rupture in the oil cooler.
Conclusions
The investigation determined that the oil leak originated from a ruptured engine oil cooler, leading to a loss of oil pressure and prompting the precautionary landing.