ACR MLG RADIO EQUIPMENT PROBLEM RESULTED IN LOSS OF COM FREQ AND RETURN LAND USING LOST COM PROC.

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WE HAD JUST TALKED TO THE TWR AND HAD BEEN CLRED FOR TKOF. WE ROLLED DOWN THE RWY NORMALLY AND LIFTED OFF AND WERE WAITING TO BE TURNED OVER TO DEP CTL. AFTER WHAT SEEMED TO BE THE NORMAL TIME LAPSE AND THEY HADN'T TURNED US TO DEP; I TRIED TO CALL AND WE HAD NOT COM AT ALL. WE TRIED ALL 3 COM RADIOS AND THEN STARTED CHKING ALL THE CB'S. AT THIS POINT WE PUT 7600 IN THE TRANSPONDER MEANWHILE OUR INITIAL CLRNC HAD BEEN TO CLB RWY HDG TO 5000' WHICH WAS ACCOMPLISHED BY NOW. THE CAPT DECIDED TO TURN BACK TO BWI VOR AND START ON TO PHL AS WE WERE FILED IF WE COULDN'T PICK OUT THE BWI GND AREA AND BWI ARPT. AT 5000' WE WERE IN AND OUT OF THE OVCST. JUST AS WE WERE PASSING BACK OVER THE BWI ARPT WE HIT A HOLE IN THE OVCST AND COULD SEE THE GND AND ARPT AREA CLEARLY. WE THEN TURNED IN AND SET UP TO LAND ON THE RWY THEY HAD BEEN USING FOR ARRS WHEN WE LEFT A FEW MINS EARLIER. AFTER LINING UP ON FINAL THE CAPT SAW A GREEN LIGHT FROM THE TWR AND WE PROCEEDED TO LAND WITH NO INCIDENT AND RETURNED TO THE GATE.