B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 444
Confusion; Situational Awareness; Communication Breakdown
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Loss Of Aircraft Control
Flight Crew Regained Aircraft Control; Flight Crew Returned To Gate; Flight Crew Became Reoriented
Procedure; Human Factors; Equipment / Tooling
We began a normal on time pushback from [the] gate. Wired communications with Ground Crew were standard. I directed my First Officer to start engines. He was starting engine number 2 when I noticed the Wing Walker give me the hand signal for 'set brakes.' I did not set the brakes as we were still moving backward at a fast walk pace. I queried the Tug Driver over the intercom and there was no answer. Our rearward speed increased and the Wing Walker was still signaling 'set brakes'. It was then that I noticed my tug was at the Safety Zone and not connected to our aircraft.It took some time for this reality to set in as the Tug Driver showed no sense of urgency and no attempt to communicate. I thought perhaps this was another tug; not ours. I gently applied brakes and brought the aircraft to a smooth stop. My First Officer and I were confused and a bit shocked at what had just occurred. I signaled my Ground Crew repeatedly to reconnect so I could ask what happened. They repeatedly refused and walked away.  After discussion with my Dispatcher and the Chief Pilot I decided to return to the gate to investigate what happened and have Maintenance inspect our nose gear.  Maintenance found nothing wrong with the nose gear. Ground Operations Supervisor told me that the Crew had not secured the tow bar correctly resulting in a disconnect. PLEASE RECOGNIZE MY EMPHASIS!This could have been a tragedy. The error with the tow bar was just the start. The Tug Driver should have communicated via intercom with urgency the moment this happened. He delayed and his headset cord detached from the aircraft.  At that point he and the entire Ground Crew should have recognized this as an emergency. They all should have signaled by hand 'stop!'  Instead; the Tug Driver remained seated and became a spectator. The Wing Walker signaled 'set brakes'. Had I complied with his signal the Flight Attendants most likely would have been injured. There was also a possibility of tail strike (yes; we were moving that fast). Had we been in proximity of another aircraft or any obstacle the collision would have occurred before I knew what happened.Ground Crew involved need to be retrained and counseled. Their failure to properly secure the tow bar resulted in tow bar separation. Their failure to recognize this as an emergency and act accordingly put our aircraft and passengers in danger. Their refusal to communicate with me afterward was just unprofessional.
The training of Ground/Ramp Crew needs to stress the importance of communication with the Flight Crew anytime the aircraft is moving. The need to contact the Flight Crew by any means necessary when the tow bar becomes detached during pushback should be understood as urgent to prevent an injury; incident or accident.
B737 flight crew reported the aircraft became disconnected from the tow bar during push back; and the ramp crew was deficient in communication to the crew about the urgency of the situation.