Cirrus Design Corp SR22 N358CD accident near Lexington, Kentucky

Probable cause

Maintenance personnel's failure to properly inspect and clean the engine ignition harness spark plug terminals, which resulted in a partial loss of engine power during an attempted takeoff.

NTSB analysis

The private pilot reported that he conducted a preflight inspection and engine-run-up with no anomalies noted. The pilot then taxied the airplane to the runway and began the takeoff roll for his planned personal cross-country flight. The airplane lifted off the runway and climbed to about 200 ft above ground level, at which point, the engine "backfired" several times, followed by a partial loss of power. The pilot chose to discontinue the flight, retarded the throttle to idle, and initiated a descent to land on the remaining runway; however, the pilot was unable to stop the airplane, and it overran the runway and collided with the precision approach path indicator lights and a snowbank.

Postaccident test runs of the engine with a new set of magnetos and the original ignition harness revealed that the likely cause of the loss of engine power was related to the ignition harness. Subsequent examination of the ignition harness revealed the presence of radial carbon tracks on the sleeves of 8 of the 12 terminals on the harness. The harness and its terminal wells were in generally dirty condition, which likely resulted in spark plugs erratically misfiring. Although one of the engine's magnetos internal mechanisms was damaged, the damage was likely the result of the engine misfiring.

According to an engine manufacturer service bulletin (SB), the ignition harness spark plug terminals should be removed, inspected, and cleaned at each annual inspection. The engine logbook indicated that the spark plugs were "cleaned, gapped, and inspected" during the last annual inspection, which was completed about 14 flight hours before the accident. However, the logbooks did not note compliance with the SB or whether the ignition harness spark plug terminal, and not just the spark plugs, had been inspected and/or cleaned. Given the generally dirty condition of the ignition harness spark plug terminals, it is likely that maintenance personnel did not properly inspect and clean the ignition harness terminals in accordance with the SB.

Text from the NTSB. Open the NTSB docket for ERA15LA134 for the full record.