Failed Spark Plugs

The following is derived from maintenance facility submissions to the FAA’s Service Difficulty Reports database.

Sunday, December 24, 2023 at 08:00 AM ET

Verified

The U.S. Coast Guard has not yet located a missing Cirrus SR22T that was last tracked heading toward the Gulf of Mexico. Cirrus Aircraft

Key Takeaways:

Spark plug failures occurred in various forms, including missing electrode ground lugs, broken ceramics, and out-of-tolerance electrical resistance (too high or no resistance).
These failures led to significant engine issues such as rough running, loss of power, preignition, loss of compression, and severe internal engine damage (e.g., holed pistons, cylinder damage, engine contamination).
Incidents across multiple aircraft types resulted in costly repairs, including full engine replacement, highlighting the critical impact of spark plug integrity on engine safety and performance.
The reports emphasize the importance of monitoring spark plug condition, including resistance checks, and timely replacement or inspection, particularly as parts accumulate hours.

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American Champion 8GCBC Scout

Failed Electrode/Engine Damage

After a scheduled spark plugs change, pilot reported a rough engine with loss of power. Found lower plug in the #4 cylinder was missing the ground lug portion of the electrode. Inspection included cylinder borescoping, oil filter and screens. No contamination was noted. Champion REB37E plug replaced. About eight engine hours later, another rough engine event occurred, with no compression in the #3 cylinder and loss of oil. That spark plug was missing the same ground lug on the electrode. It appears the lug became lodged between the piston and ring, holing the piston and cylinder wall.