Narrative:

During the pushback from gate xz, the tow bar became disconnected from either the tug or the nose gear. I had just started the left engine during the push out and the tug was turning us and pulling forward at the same time. It is not clear from ground man communications whether the tow bar came off accidentally or was unhooked by the other ground man accompanying the tug driver on headset. The only signal I received was 'parking brakes, parked' from the headset man. I noticed we were still moving forward slightly and waited a second to see if he was still in a stopping mode, so as not to jerk the aircraft to a stop. He again said 'parking brakes, parked' and I then said, 'we are still rolling.' he then told me we were not hooked up any longer, so I immediately applied brakes. The tug was moving such that he was matched in speed to our speed while moving forward at the top of the alley and without a call saying we were not hooked up. I had no idea that the problem even existed until after his second call. Damage and injury were averted, but only by luck, I'm afraid. A callout or procedure needs to be addressed for this type of situation -- such as 'emergency stop' or 'tow bar has disconnected, stop and park brakes.' I find no such guidance listed in part 1 or in the operating manual under pushbacks. More careful communications need to be designed and this incident should be briefed to all affected personnel -- both ground and flight -- to avoid a more dangerous outcome.

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Original NASA ASRS Text

Title: AN MD SUPER 80 ON PUSHBACK FROM A GATE HAD THE TOW BAR INADVERTENTLY DISCONNECT FROM THE ACFT PUTTING THE RAMP GUIDEMAN AND TUG DRIVER AT RISK OF INJURY.

Narrative: DURING THE PUSHBACK FROM GATE XZ, THE TOW BAR BECAME DISCONNECTED FROM EITHER THE TUG OR THE NOSE GEAR. I HAD JUST STARTED THE L ENG DURING THE PUSH OUT AND THE TUG WAS TURNING US AND PULLING FORWARD AT THE SAME TIME. IT IS NOT CLR FROM GND MAN COMS WHETHER THE TOW BAR CAME OFF ACCIDENTALLY OR WAS UNHOOKED BY THE OTHER GND MAN ACCOMPANYING THE TUG DRIVER ON HEADSET. THE ONLY SIGNAL I RECEIVED WAS 'PARKING BRAKES, PARKED' FROM THE HEADSET MAN. I NOTICED WE WERE STILL MOVING FORWARD SLIGHTLY AND WAITED A SECOND TO SEE IF HE WAS STILL IN A STOPPING MODE, SO AS NOT TO JERK THE ACFT TO A STOP. HE AGAIN SAID 'PARKING BRAKES, PARKED' AND I THEN SAID, 'WE ARE STILL ROLLING.' HE THEN TOLD ME WE WERE NOT HOOKED UP ANY LONGER, SO I IMMEDIATELY APPLIED BRAKES. THE TUG WAS MOVING SUCH THAT HE WAS MATCHED IN SPD TO OUR SPD WHILE MOVING FORWARD AT THE TOP OF THE ALLEY AND WITHOUT A CALL SAYING WE WERE NOT HOOKED UP. I HAD NO IDEA THAT THE PROB EVEN EXISTED UNTIL AFTER HIS SECOND CALL. DAMAGE AND INJURY WERE AVERTED, BUT ONLY BY LUCK, I'M AFRAID. A CALLOUT OR PROC NEEDS TO BE ADDRESSED FOR THIS TYPE OF SIT -- SUCH AS 'EMER STOP' OR 'TOW BAR HAS DISCONNECTED, STOP AND PARK BRAKES.' I FIND NO SUCH GUIDANCE LISTED IN PART 1 OR IN THE OPERATING MANUAL UNDER PUSHBACKS. MORE CAREFUL COMS NEED TO BE DESIGNED AND THIS INCIDENT SHOULD BE BRIEFED TO ALL AFFECTED PERSONNEL -- BOTH GND AND FLT -- TO AVOID A MORE DANGEROUS OUTCOME.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.