Tempest Aero Group has issued Service Bulletin SB-012 calling for immediate inspection of specific spark plug lot numbers manufactured between May 5, 2026 and July 29, 2026, after field reports identified cracking in affected units.
The bulletin is directed at aircraft owners and operators, engine overhaul facilities, engine maintainers, and engine manufacturers. Tempest states the inspection must be completed prior to the next flight for any affected plugs. Cracked plugs must be replaced before return to service.
According to the bulletin, a cracked spark plug that goes undetected could result in engine damage and possible loss of power — a serious concern in single-engine piston operations where there is no redundancy.
The scope covers all Tempest spark plugs bearing the part numbers and lot codes listed in the bulletin's Table 1, regardless of when the plug was installed, what engine model it is in, or what airframe it is installed on. Plugs purchased before May 5, 2026 are not affected.
Tempest states the cracking condition had not previously appeared in its production history. After receiving field reports, the company initiated an investigation, identified the root cause, and has implemented corrective actions to its manufacturing and inspection processes. The bulletin does not specify the nature of the manufacturing defect or how many units are potentially affected.
For maintenance technicians working piston aircraft — particularly those supporting flight training operations, charter, or GA fleets — the lot code check is the first step. Any plug falling within the affected date range and matching a listed part number requires physical inspection before that aircraft flies again.
