Skyhawk 172/Cutlass 172
Flight Crew Commercial; Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor
Flight Crew Last 90 Days 112; Flight Crew Total 440; Flight Crew Type 127
Aircraft Equipment Problem Less Severe; Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Taxiway
Air Traffic Control Provided Assistance; Flight Crew Took Evasive Action; General Flight Cancelled / Delayed; General Maintenance Action
Procedure; Aircraft
The aircraft to be used for training was previously squawked for a front nose wheel shimmy. Maintenance at our flight school looked it over as well as the main wheel brakes prior to my scheduled flight and said that the aircraft was safe to fly. My student and I followed the correct procedures and checklists for engine-start and taxi. Both the student and I checked the brakes prior to taxi and found them functioning properly. As we were on our taxi for departure and while making a right-turn (at a safe speed) onto D from B; our left brake locked and caused our aircraft to exit the taxiway just east of [taxiway] pointing toward the active runway. I immediately reduced power and pulled the mixture to I.C.O to stop our aircraft. I reported our deviation to Ground Control and requested assistance and then informed them that I would contact our school. The school's maintenance personnel helped us unlock the brake and we were able to taxi back to the school ramp. Maintenance then investigated the issue in more detail.
Pilot reported a main wheel brake locked up on taxi; causing a taxiway excursion.