ERA11FA414 · Cirrus Design Corp SR22

The surviving passenger stated that the pilot flew the airplane on an uneventful 56-minute flight earlier on the day of the accident. According to data from the multifunction display, the oil pressure was in the normal green arc range (30 to 60 psi) during the entire flight. After landing, no maintenance or servicing was performed. Before takeoff for the accident flight, the pilot performed a walk-around inspection of the airplane, which would require, in part, a check of the oil quantity.

According to GPS and other recorded flight data, about 17 minutes after takeoff, the oil pressure decreased below the lower end of the normal operating range; at the time, the airplane was flying in an easterly direction about 10 nautical miles west of an airport with runways of more-than-adequate length for the pilot to divert. Rather than divert, the pilot continued toward the destination. Although the oil temperature remained in the normal operating range, the oil pressure continued to decrease. Both indications would have been available to the pilot either on the multifunction display or on the analog combination oil pressure/oil temperature gauge.

While the airplane continued toward the destination, the oil pressure decreased to 10 psi, and the pilot maintained the engine power setting at 2,400 rpm (the maximum setting is 2,700 rpm). About 46 minutes after takeoff, with the engine rpm still set at 2,400 rpm, the pilot declared an emergency and advised the controller that smoke was coming from the engine. Unable to fly to suggested airports, the pilot initiated an approach for a forced landing to a large open area containing east/west- and north/south-oriented paved roads.

Witnesses reported that the engine was sputtering and “coughing” but did not note smoke trailing the airplane. For the last 1 minute 12 seconds of flight, the engine rpm decreased from 2,400 to 1,700. While descending with the autopilot disengaged and at 74 knots indicated airspeed, the airplane banked 55 degrees to the right, stalled, pitched nose-down, and impacted the ground.

Examination of the wreckage revealed oil covering the bottom left side of the fuselage from the engine firewall to the tailcone, consistent with the crankcase being pressurized and blowing oil out of the air/oil separator. Examination of the engine revealed that the oil gauge rod and cap assembly had separated from the oil filler tube and was found near the engine and propeller impact crater. Neither the oil gauge rod and cap assembly nor the oil filler breather tube were impact damaged, suggesting that the assembly was improperly secured. Although the No. 4 cylinder piston was fractured and the fracture surfaces exhibited widely spaced crack propagation marks consistent with progressive crack growth under cyclic stresses, the cyclic load was at or above the yield strength of the material. Therefore, the No. 4 cylinder piston did not contribute to the loss of engine oil supply. Examination of the ignition, lubrication, air induction, and fuel injection systems did not note any discrepancies that contributed to the catastrophic failure of the engine.

The catastrophic failure of the engine was consistent with oil starvation due to the crankcase becoming pressurized because of an unsecured oil gauge rod and cap assembly. Postaccident examination of the pistons, piston rings, and crankshaft nose seal did not indicate other typical scenarios of crankcase pressurization. A previous NTSB accident investigation of a different airplane with the same engine model determined that an unsecured oil cap allowed the crankcase to become pressurized and the oil to be vented overboard, causing subsequent catastrophic failure of the engine due to oil starvation.

The pilot’s decision to continue the flight with decreasing or low oil pressure rather than land at a suitable airport nearby and his continued operation of the engine at a high rpm setting contradicted the emergency procedures section of the pilot operating handbook and Federal Aviation Administration-approved flight manual, which contributed to the catastrophic failure of the engine.

Although the airplane was equipped with an airframe parachute, an acquaintance of the pilot reported that the pilot would only use it in the event of a structural issue that rendered the airplane uncontrollable. Otherwise, if it were controllable, the pilot intended to hand-fly the airplane to landing. If the pilot had deployed the airframe parachute, he may have increased the likelihood of a successful emergency landing.

Verbatim NTSB analysis and probable cause from the NTSB dataset