Aviation Spark Plugs
An aviation spark plug has more in common with an industrial igniter than with an automotive plug. Aviation plugs run harder, run longer, and carry a higher certification burden. Correct selection, rotation, and cleaning extend plug life dramatically and save cylinder wear.
Types
- Massive electrode — the economical choice. Solid center electrode plus a solid ground. Longer life in low-lead avgas; forgiving of fuel-system variation.
- Fine wire — platinum or iridium alloy center electrode with narrow ground straps. Improved ignitability for hot-start and at-altitude performance, longer service life, significantly higher price.
Major manufacturers
- Champion Aerospace — the long-standing incumbent. REM (massive) and REB (fine wire) families.
- Tempest — AeroPerformance brand. URHM (massive) and UREM (fine wire) families. Tempest fine-wire plugs are widely reported to run longer than Champion equivalents at a comparable price.
Thread reach, size, and heat range
The correct plug is specified by engine model, not by aircraft model. Lycoming O-320 uses a different thread reach from O-540. Intermix across families is always wrong.
Inspection and rotation
- Pull all plugs in sequence.
- Inspect ceramic, visible lead deposits, electrode wear.
- Clean with an approved plug cleaner (abrasive blast for massive; solvent only for fine wire).
- Gap-test with the correct feeler — fine wire has a different gap than massive.
- Rotate top-to-bottom to reverse polarity wear; retorque to 360 in-lb (check the engine manual).
Shop plugs
Search the catalog by plug P/N (for example, REM38S or URHM38S). Not sure which plug your engine takes? Use the Aircraft Finder or email us.
