Accident Overview
On October 10, 2021, at 1210 eastern daylight time, a Flight Design GMBH CTLS, registration N121YT, was substantially damaged during an accident near Greenville, South Carolina. The private pilot sustained minor injuries. The airplane was being operated as a personal flight under Title 14 Code of Federal Regulations Part 91.
Flight Details
According to the pilot, an annual condition inspection had been conducted at Twin Lakes Airport (S17), Graniteville, South Carolina. After a preflight inspection that revealed no anomalies, the pilot departed for Henderson, North Carolina. Approximately 18 miles south of his destination, the engine oil pressure dropped to zero. The pilot turned toward Greenville Downtown Airport (GMU) and declared an emergency. The engine continued to run for about 4 to 5 minutes before it “seized.” The pilot informed GMU that he would not be able to reach the airport and turned toward an open clearing. He deployed the ballistic parachute at about 500 ft above ground level (agl). Shortly after deployment, the airplane descended into pine trees and was suspended approximately 50 ft above the ground about 9 miles north of GMU. The pilot climbed out of the side window and was rescued by local first responders.
Postaccident Examination
A Federal Aviation Administration inspector examined the airplane and found substantial damage to the fuselage and left wing. The airplane was recovered to a secure facility for further examination. The engine was in good overall condition but had oil staining down the right side of the airplane from the engine cowling to the horizontal stabilizer. The hose from the oil tank to the oil thermostat and the hose from the oil thermostat to the oil cooler were found disconnected from the oil thermostat. The hoses, barbs, and hose clamps were undamaged and intact. A representative from the engine manufacturer stated that with the hoses disconnected, it would be reasonable to expect the engine to seize after about 3 to 4 minutes at maximum power due to loss of lubrication.
Engine Condition
The valvetrain components in the cylinder heads were dry and lacked lubrication, and the No. 1 valve cover contained metallic debris. No other anomalies were noted within the cylinder heads or their components. All cylinders were removed, and the cylinder bores were dry without oil lubrication. The crankshaft could not be rotated by hand. After removing the cylinders, the No. 3 connecting rod bearing was found to have failed and was discolored consistent with exposure to excessive heating. The No. 3 piston and connecting rod were removed, after which the crankshaft could be rotated by hand. Approximately 2.5 quarts of oil were drained from the oil tank. The oil cooler system was not breached or damaged.
Engine Data Monitor
Data from a Dynon EMS-D120 engine data monitor showed that about 62 minutes after recording began on the accident flight, and about 53 minutes after takeoff, oil pressure dropped from 51 pounds per square inch (psi) to 0 psi in 55 seconds and remained near 0 psi for the remainder of the recording. Engine rpm decreased from about 5300 rpm to 0 rpm over approximately 5 minutes, consistent with the pilot’s description of the loss of engine power.
Maintenance Records
Review of the airplane’s maintenance records revealed that a condition inspection had been completed two days before the accident, on October 8, 2021. The accident flight was the first flight after this inspection. The mechanic who performed the inspection reported that he did not remove any hoses from the oil thermostat, that he checked them for security before returning the airplane to service, and that they did not come off when he “tugged” on them. On October 14, 2020, the rubber hoses servicing the engine’s oil and fuel systems were replaced in accordance with the engine manufacturer’s 5-year requirement. The airframe had accumulated 152 hours since that work.