DISPATCHED WITH INOP APU; INEXPERIENCED GND CREW FAIL TO COMPLY WITH NON-APU ENG START AND PUSHBACK PROCS. BROKEN TOWBAR RESULTS.

Narrative

UPON RECEIVING THE ACFT IT HAD AN MEL FOR APU INOP. WE REVIEWED THE QRH CHKLIST FOR STARTING WITH EXTERNAL PNEUMATIC SOURCE AND OVERHEAD PANEL WAS SET. IT WAS HOT IN THE ACFT AND I ASKED THE GND CREW TO LEAVE THE GND AIR CONDITIONER HOOKED UP AS LONG AS POSSIBLE BECAUSE WE HAD EVERY SEAT FULL. WE CLOSED UP AND I TOLD THEM THEY COULD PULL THE GND AIR CONDITIONER AND GIVE ME THE AIR FOR ENG START. THE AIRPLANE WENT DARK AS THEY ALSO PULLED THE GND PWR. LATER; THEY GOT IT HOOKED BACK UP AND SAID THEY WERE SORRY THEY HAD NEVER DONE THIS BEFORE. WE HAD NUMEROUS COMPUTER FAULTS AND IT TOOK ABOUT 8 MINS TO CLR THE MESSAGES. THEY GAVE US THE AIR AND WE WERE CLR ON 2 ENG FOR START. AFTER #2 ENG WAS RUNNING I SAID YOU CAN PULL THE AIR AND ELECTRICS AND LET ME KNOW WHEN YOU'RE READY TO PUSH. BUT HE SAID HE COULDN'T HEAR ME OVER THE ENG. I SAID IT AGAIN LOUDER AND AFTER SOME HESITATION HE SAID OK AND ABOUT A MIN LATER HE SAID THEY WERE READY TO PUSH. I RELEASED THE BRAKE AND PUSHBACK COMMENCED. A FEW SECONDS LATER I HEARD THE TOWBAR BREAK AND I SAID; 'TALK TO ME; WHAT'S HAPPENING?' I STOPPED AND SET THE PARKING BRAKE. HE SAID THE TOWBAR CAME LOOSE BUT THERE WAS NO DAMAGE TO THE ACFT. I SAID I WANTED A QUALIFIED PERSON TO TELL ME. I CALLED MAINT TO COME AND LOOK AT IT. MAINT CAME; SAID THERE WAS NO DAMAGE; AND WE DEPARTED.