A DC9 ON PUSHBACK HITS TUG WHEN THE TOW BAR IS DISCONNECTED WITHOUT THE FLC'S KNOWLEDGE.

Narrative

WE WERE PUSHING BACK FROM GATE AT DTW. THE APU WAS ON MEL STATUS; THEREFORE BOTH ENGS WERE STARTED AT THE GATE USING EXTERNAL AIR SOURCE. IT WAS A NORMAL PUSHBACK; PERHAPS A LITTLE SLOW; WITH POOR OUTSIDE VISUAL REF AND USING ABNORMAL PROCS ONCE WE HAD NO APU. DURING PUSHBACK THERE WAS A LOT OF EXTERNAL NOISE FEEDING THROUGH THE INTERCOM WHICH MADE COMS BTWN THE TUG DRIVER AND THE CAPT SOMEWHAT DIFFICULT. AS I COMPLETED MY NORMAL FLOWS AND WAS READY FOR THE CAPT TO CALL FOR THE BEFORE TAXI CHK; THE ACFT IMPACTED THE TUG CAUSING DAMAGE TO THE RADOME. AT SOME POINT DURING THE COURSE OF THE PUSHBACK; WE HAD A BREAKDOWN IN COMS WHEREAS THE TOW BAR WAS DISCONNECTED WITHOUT THE BRAKES BEING SET. CONTRIBUTING FACTORS: APU NOT BEING AVAILABLE. IT REQUIRED THE USE OF ABNORMAL PROCS. LATE NIGHT OP. PERHAPS BEING A LITTLE TIRED MIGHT HAVE CONTRIBUTED IN THE CHAIN OF EVENTS. COMS: POOR AUDIO QUALITY ON THE DC9 INTERCOM BTWN FLT DECK AND GND CREW. AS A FO I HAVE MY EAR PIECE DISCONNECTED DURING GND OPS TO PREVENT SERIOUS DAMAGE TO MY EAR DRUM. ALSO SINCE ENGS WERE ALREADY ON LINE; THE FEEDBACK COMING THROUGH THE INTERCOM MADE IT DIFFICULT FOR THE CAPT TO UNDERSTAND WHAT THE MECH WAS SAYING. POS OF THE TUG 90 DEGS RELATIVE TO THE ACFT: IT SEEMED AS IF THE PUSHBACK HAD NOT BEEN COMPLETED; THEREFORE IT APPEARED AS IF THE TUG WAS STILL MOVING; BUT TO OUR SURPRISE THE TOW BAR HAD BEEN DISCONNECTED. POSSIBLE CORRECTIVE SOLUTIONS: ALWAYS FLY WITH AN APU. EXERCISE EXTREME VIGILANCE AND CAUTION -- ESPECIALLY DURING ROUTINE GND OPS SUCH AS A PUSHBACK.