A tiny gear in regional jets keeps wearing out, forcing airlines to check them early

US aviation regulators are ordering inspections of a specific part in regional jet engines after reports of premature wear. Airlines must now check a rubber bull gear wheel in the horizontal stabilizer trim actuator, and replace it if it shows wear.

This is a small, boring change that matters because it affects the operating costs and maintenance schedules for a specific class of aircraft. Airlines now have to pull planes out of service for inspections and replace parts more often than planned. These small, unexpected maintenance costs add up, especially for regional carriers that operate on thin margins.