B737 Undifferentiated or Other Model
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 198; Flight Crew Total 1727; Flight Crew Type 2724
Communication Breakdown
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Loss Of Aircraft Control
Flight Crew Regained Aircraft Control
Equipment / Tooling; Procedure; Human Factors
At [time] received 'ramp ready' and completed before push checklist. Received push clearance and communicated with ramp that 'brakes released; cleared to push'. Normal push forces were felt for several seconds followed by a slightly unusual jolt. The tug brought the aircraft to a relatively quick stop. I queried 'did something break'? The tug driver responded; 'I think maybe the shear pin broke'. The aircraft was stationary and I asked the First Officer to cancel our push clearance with ZZZ ramp control. I told the ramp 'pushback canceled'. I don't recall receiving a response from ramp. After approximately 15 seconds; the aircraft began moving aft and I restated 'Stop. Pushback canceled. Cancel Push.' The tug driver stated 'Set brakes. Set Brakes!' The aircraft had moved 3-6 feet in this time. Normal pedal braking was applied to smoothly stop the aircraft and the parking brake was set. Ramp then stated; 'I thought you had set your brakes'. I replied 'I wasn't told to set brakes'. A new tow bar was located; maintenance arrived and provided an inspection; and pushback continued within 3-5 mins. No further issues.
B737 Captain reported on pushback a miscommunication from the ground crew resulting in an uncontrolled movement of aircraft.