CE-560 air taxi flight crew reported a left brake malfunction during a taxi turn which resulted in a taxiway excursion in the grass. A tug towed the aircraft to the ramp.
Synopsis
CE-560 air taxi flight crew reported a left brake malfunction during a taxi turn which resulted in a taxiway excursion in the grass. A tug towed the aircraft to the ramp.
Narrative
Taxiing on Taxiway 1 at ZZZ. We crossed RNWY XX-XY going West on Taxiway 1. Applied brakes to slow the aircraft prior to the 90 degree turn to go Southbound on taxiway 1. Applying brakes; initially the aircraft slowed; then you felt the left brake pedal release and the nose of the aircraft turned toward the right... pushed on the brakes a little and pushed the left rudder pedal to correct. The right brake worked as expected and the left brake worked but not as well; and the aircraft turned more to the right; as the right brake was working better than the left. The nose of the aircraft left the taxiway surface was was 24' into the grass on the right side of taxiway 1. We talked with the ground controller; and had a tug come and recover the aircraft back to the FBO. Made calls to company and spoke with our maintenance team. We taxied the aircraft and operationally checked the brakes and Antiskid. We were unable to reproduce the brake issue. Under Maintenance direction I wrote in the maintenance log 'The left brake was weak. Operationally checked and were not able to duplicate.' We relocated the aircraft the next morning from ZZZ to ZZZ1 so that the aircraft could be further diagnosed.
Second reporter narrative
While Taxiing westbound on taxiway 1 at ZZZ; after crossing runway XX/XY; the Captain applied brakes to slow for a left turn southbound on Taxiway 1. The aircraft began to turn right as the left brake seemed to lose effectiveness. Despite additional braking and rudder input the nosewheel rolled slightly off the taxiway into the grass; stopping about two feet off the pavement. Ground control was advised; and a tug repositioned the aircraft to the FBO. No damage or injuries occurred. Once back at the FBO the captain made calls to company and spoke with the maintenance team under their direction we operationally checked the brakes and the Antiskid system and could not duplicate the problem. That Evening the captain and maintenance completed the paperwork to allow for the aircraft to be relocated for maintenance the next morning at ZZZ1.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.