CEN20LA020

According to the pilot, about 2 minutes after leveling off at a cruise altitude of 3,000 ft above mean sea level (msl), the engine shook and vibrated. He switched his multifunction display (MFD) to the engine parameter page and all engine indications appeared normal. About 2 minutes later, the indication of the No. 5 engine cylinder turned from green to red. He then reported the engine problem to air traffic control and announced his intentions to divert to an alternate airport. Unable to maintain altitude he began a descent. Shortly thereafter, the engine appeared to operate normally, and he was able to climb about 200 ft per minute before the shaking returned. The airplane descended out of the clouds about 1,200 ft msl, and the pilot deployed the airplane’s parachute system. The airplane impacted the ground and was substantially damaged. A postaccident examination of the engine revealed that the No. 5 piston head exhibited cleaning and damage consistent with detonation, while the No. 1 cylinder exhibited signatures consistent with the initial phase of detonation. The magneto timing on the engine measured at 27° before top center (BTC) rather than the factory specification of 24° BTC. According to the engine manufacturer, coupled with a rich mixture, this could result in detonation. When asked to describe the engine leaning procedure used, the pilot stated that he would lean the mixture to the blue line on the MFD. According to the airframe manufacturer, the Lean Assist blue line does not take into account engine timing. It is likely that the incorrect engine timing, when combined with a mixture setting that was too rich for the engine condition, resulted in detonation. Investigators did not establish the last time the engine timing was adjusted.

On November 22, 2019, about 1338 central standard time, a Cirrus SR-22 airplane, N969JM, was substantially damaged when it was involved in an accident near Tyler, Texas. The pilot and passenger sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, about 2 minutes after leveling off at a cruise altitude of 3,000 ft above mean sea level (MSL), the engine “shook real good” which was followed by a “big vibration.” He switched his multifunction display (MFD) to the engine parameter page and all engine indications appeared normal. About 2 minutes later, the depiction of the No. 5 engine cylinder turned from green to red. He immediately checked the manifold pressure which indicated 28.5 inches of mercury or according to the pilot, about 2/3 full power. The pilot then reported the engine problem to air traffic control (ATC) and announced his intentions to divert to an alternate airport. Unable to maintain altitude he began a descent. Shortly thereafter, the engine appeared to smooth out and he was able to climb about 200 ft per minute before the shaking returned. Subsequently, the pilot declared an emergency with ATC and advised of his intention to deploy the Cirrus Airframe Parachute System (CAPS) when he reached 1,000 ft msl. The airplane descended out of the clouds about 1,200 ft msl and the pilot identified a field to his right. He turned toward the field and tried to utilize the high boost fuel pump to restore power, to no avail. He then lowered the nose of the airplane and deployed the CAPS when the airplane was between 550 ft and 650 ft agl. The airplane impacted the ground underneath the CAPS canopy and came to rest upright. The passenger extricated the unconscious pilot and got away from the airplane. The parachute caught the wind and carried the airplane about 1/4 mile across the field into a stand of trees. The initial impact resulted in substantial damage to the fuselage, and the subsequent travel across the field and into the trees resulted in further damage to the fuselage and substantial damage to both wings. A post-accident examination of the airplane’s Continental TSIO-550 series engine revealed that the No. 5 piston head exhibited cleaning and damage consistent with detonation, while the No. 1 cylinder exhibited signatures consistent with the initial phase of detonation. Also, the Nos. 5 and 6 connecting rods exhibited movement consistent with bearing liberation. The fuel manifold and fuel injection nozzles were placed on a production flow bench and flowed at production specifications. The magneto timing on the engine measured at 27° before top center (BTC) rather than the factory specification of 24° BTC. According to the engine manufacturer, coupled with a rich mixture this could result in detonation. When asked to describe the engine leaning procedure used, the pilot stated that he would lean the mixture to the blue line on the MFD. Accordingto Cirrus, the Lean Assist blue line does not take into account engine timing. According to the Cirrus Perspective cockpit reference guide, when the “ASSIST” key is selected, the system highlights the number and places a light blue box around the exhaust gas temperature (EGT) readout of the cylinder with the hottest EGT. There is a value for the deviation from peak EGT to assist the pilot in knowing the difference between the peak temperature and the current temperature for the peaked cylinder. “The system continues to detect peak EGTs for each cylinder lean of peak as the fuel flow is decreased, and the peak of each cylinder’s EGT is indicated by a light blue marker on the graph.” The airplane was equipped with a Heads-Up Technologies recoverable data module (RDM) that recorded flight, engine, and autopilot parameters in one second intervals. A review of the data revealed that around 1314:45, the No. 5 cylinder head temperature (CHT) began to increase, the exhaust gas temperature (EGT) began to decrease, and engine oil pressure began to decrease. After a brief recovery of the CHT and EGT values, which lasted about 2 minutes, the No. 5 cylinder failed. Shortly after the No. 5 cylinder failure, the No. 1 cylinder failed.