B737-800
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Confusion; Communication Breakdown; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Aircraft Aircraft Damaged; Flight Crew Returned To Gate; General Maintenance Action
Equipment / Tooling
FO (First Officer) just returning from lav and tug driver checked in with proper verbiage and advised cleared to release brakes. I replied with Brakes released simultaneously releasing brakes; then standby we have a couple things to do and I'll be back with you in a minute or two. FO sat down and we started to run Before Starting Engines checklist. By 2nd item on the checklist; in the inter phone I could hear STOP STOP STOP STOP which I wondered who or why this was being said to whom. Within a second or two; I realized that it seemed we were commencing pushback from gate. Upon this realization and with all of the yelling STOP; I grabbed the michrophone and advised that I had not told him to push and to stop. By this time; I realize that the tug is proceeding past aircraft left and jackknifing the towbar and has gone out of control. The tug then comes to a stop and I set the brakes as the driver advises me that the brakes failed on the tug. He is no longer paying attention to me and the whole operation stopped. My FO called ramp and advised them that we were disabled partially pushed back and he also requested maintenance.Throughout the next 45 minutes numerous maintenance; station; and ramp personnel came to [examine things]; take pictures; and generally gawk. I talked with two maintenance personnel about their plan and kept the FA's (Flight Attendants) and passenger advised every step of the way. Finally with the damage to the tow bar attach point and after maintenance pinning the gear and working me through to test the nose wheel steering; the decision was made to start engines and taxi about 30 feet back into the gate. This was accomplished successfully 52 minutes after commencing initial brake release.It seems that this occurred due to equipment or Human Failure in operation of the pushback tug.
B737-800 Captain reported that during push-back the tug had a brake failure.