The FAA on Aug. 26 will propose rudder pedal assembly inspections on more than 500 U.S.-registered Bombardier 50-seat regional jets to prevent a key part cracking from repeated use when pilots set the parking brake.

The draft order, based on a Transport Canada (TC) directive issued in May, focuses on the assembly’s pedal tubes. TC said it received two reports of in-service pedal tube fractures at the connecting rod attachment point. In both cases, the cracked tubes were on the pilot’s (left) side of the cockpit.

Fatigue testing determined the cracking came from repeated loads induced during parking brake applications, which require depressing the top parts of both rudder pedals. “Therefore, only the rudder pedal tubes on the pilot’s side are vulnerable to fatigue cracking, as the parking brake is primarily applied by the pilot,” TC said.

Similar to the TC mandate, the FAA proposes a tiered inspection schedule based an aircraft’s service history. Bombardier regional jets with less than 20,000 cycles would need initial inspections within 3,000 cycles, while the most-used airframes—those with at least 37,000 cycles—would require checks within 300 cycles.

Operators would have the choice of detailed or eddy current inspections. Crack-free tubes would be checked again every 600 cycles following visual checks, or 1,000 cycles after eddy current inspections. Any cracked tubes would require immediate replacement. Replacing the tubes would cost about $3,400 per aircraft, the FAA says.

Operators can solve the problem by replacing both pilot-side rudder bar assemblies.

Both the FAA and Canadian directives are based on Bombardier service instructions issued in April.