What happened
During the landing phase, the first officer was operating the aircraft from the left seat and landed slightly to the left of the runway centerline. The check airman on board observed that the aircraft would be unable to exit at the intended taxiway and instructed the first officer to reduce speed and continue rolling toward the subsequent taxiway.
The first officer reported that the brakes were not functioning correctly, causing the airplane to drift further to the left. Although the check airman attempted to take control of the aircraft, they were unable to use the brakes effectively because the first officer was applying the brakes in a manner that overrode the check airman's inputs. Consequently, the aircraft departed the runway approximately 200 feet before the end of the pavement, resulting in a collision with a taxiway sign and light.
The investigation
An examination of the braking system conducted by the airline's chief maintenance inspector identified two specific mechanical failures: a broken return spring within the right master cylinder and a leaking lock-o-seal.