Tempest Aero Spark Plug Cracking SB-012

TO: Aircraft Owners and Operators, Engine Overhaul Facilities, Engine Maintainers, Engine Manufacturers
SUBJECT
This Service Bulletin describes a potential cracking problem in specific lot numbers of Tempest® Spark Plugs manufactured between May 5, 2026 and July 29, 2026. It recommends immediate inspection of the affected spark plugs prior to your next flight and replacement of any cracked spark plugs. No action is required for Tempest® Spark Plugs purchased prior to May 5, 2026.
REASON
There have been limited reports of spark plugs exhibiting cracks. Failure to detect and replace a cracked spark plug could potentially result in damage to the airplane engine and possible loss of power.
SCOPE
This Service Bulletin applies to all Tempest® spark plugs bearing the part numbers and corresponding lot codes listed in Table 1 (page 2), regardless of date of installation, engine model, or airframe application. This is the original issue of SB-012.
BACKGROUND
There have been field reports of cracks in Tempest® spark plugs. 
This condition has not previously been observed or reported in our production history. Upon notification of the issue, Tempest Aero Group initiated an investigation and identified the root cause. Tempest Aero Group has implemented the necessary corrective action to the manufacturing and inspection processes and is issuing this Service Bulletin to address any affected in-service spark plugs.

See attached document for more information.