B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 220; Flight Crew Total 20000; Flight Crew Type 11300
Communication Breakdown; Confusion
Ground Event / Encounter Loss Of Aircraft Control
Flight Crew Regained Aircraft Control; Flight Crew Became Reoriented; General Maintenance Action
Equipment / Tooling; Human Factors; Procedure
While being pushed back the tow bar disconnected from the Push Back Unit. Just as the nose of the aircraft cleared the Passenger Boarding Bridge the aircraft made a quick 90 Deg turn to aircraft left relative to the lead in line. This sharp turn was odd since we where in the early phase of the push back procedure and close to aircraft on adjacent gates. It was a smooth almost floating feeling as the aircraft made the sharp 90 Deg turn without the normal jerking motion that you normal feel on push backs. At that moment the pushback tug driver said over the headset; 'We're disconnected'. I said; 'As in BREAK AWAY?' He responded that; 'The Tow Bar has disconnected from the Push Back Unit and the tow bar is still connected to the aircraft.' I quickly stopped the movement of the aircraft by getting on the brakes and setting the parking brake. I then asked if all ramp personnel where ok. He replied that they were fine and the aircraft DID NOT hit anything. We advised Ramp that we had a break away and would like to stay in our current location until Maintenance could inspect the aircraft. We called to have Maintenance come and inspect the nose wheel and nose landing gear for any possible damage. Maintenance reported that there was no damage and we were safe to continue our flight.  After the tow bar was reattached; push back crew advised ready; requested and received pushback clearance; we continued the flight without incident.
B737 Captain experiences a breakaway during pushback; but the ground crew does not convey that information in a succinct or timely manor. Time is not a factor however and the aircraft is stopped without damage.