What happened
On 18 December 2018, a Cirrus SR22, registration N842CD, was conducting a local pleasure flight from Toussus-le-Noble. The flight, carrying a pilot and one passenger, initially proceeded without issue, flying along the Channel coast. However, approximately 50 minutes into the flight, the engine oil pressure began a steady decline from 54 PSI toward zero.
Initially, the oil temperature remained stable, which led the pilot to believe the pressure drop might be a sensor malfunction. After a period of monitoring, the engine power decreased, and the pilot initiated a diversion to Dreaux Vernouillet aerodrome. Shortly thereafter, the oil temperature began to rise rapidly. As the oil pressure dropped below 10 PSI, a red warning light activated, and the engine shut down completely.
At an altitude of approximately 1,700 ft, the pilot deployed the aircraft's emergency parachute. The aircraft descended vertically into a ploughed field. Upon impact, the nose gear failed, and strong winds caused the parachute to drag the aircraft onto its back. The pilot and passenger successfully evacuated the wreckage through a forced opening in a door.
The investigation
The BEA examined the wreckage and the engine components to determine the cause of the oil loss. Investigators found significant oil staining along the fuselage and underside of the aircraft. Examination of the engine revealed that the quarter-turn oil cap/dipstick was not in place; the cap was recovered near the wreckage site.
This lack of a secure cap allowed a substantial amount of oil to escape from the filler port during flight. The escaping oil entered the engine's air intake system via the filter, which was found to be saturated with oil. The investigation also reviewed the pilot's flight manual and the cockpit's Avidyne avionics interface to understand the decision-making process regarding the low-pressure warnings.
Findings
- The primary cause of the engine failure was an oil leak resulting from the oil cap being incorrectly positioned during a pre-flight check.
- The flight manual for aircraft equipped with Avidyne avionics contained instructions that were subject to interpretation, potentially leading the pilot to misdiagnose the pressure drop as a sensor error because the oil temperature had not yet risen.
- The pilot's decision to continue the flight toward the original destination was influenced by the stable oil temperature readings during the initial stages of the leak.