SMOKE IN COCKPIT AFTER AN APU FAILURE WITH A DEFERRED AIR CONDITIONING SYS MANDATES A RETURN LAND FOR THE CREW IN A DO328 DEP BOS; MA.

Narrative

PRE-EXISTING CONDITIONS: L HEAT EXCHANGER FAN DEFERRED/RECIRCULATION FAN DEFERRED. THIS REQUIRES THAT THE APU BLEED BE THE ONLY SOURCE OF CABIN AIR FOR TKOF THROUGH 1500 FT AGL. THIS ALSO MEANS THAT CABIN AIR CIRCULATION WILL BE MINIMAL UNTIL L BLEED SELECTED ABOVE 1500 FT AGL AND 160 KTS BECAUSE OF THE HEAT EXCHANGER FAN DEFERRAL. WE HAD BEEN THOROUGHLY DEICED AT THE GATE. SIT: BEFORE TKOF; I DESELECTED THE R ENG BLEED SOURCE AND SELECTED THE APU BLEED SOURCE PER DEFERRAL PROCS. THE R PACK WAS ON; THE L PACK OFF -- ALSO PER THE DEFERRAL PROCS. AT 1500 FT AGL; AS I WAS REACHING TO DESELECT THE APU BLEED AND SELECT THE L AND R ENG BLEEDS AND L PACK; APU GENERATOR OVERHEAT CREW ALERT SYSTEM APPEARED IMMEDIATELY FOLLOWED BY SMOKE ENTERING THE COCKPIT THROUGH THE VENTS BY THE WINDSCREEN. WE COMPLIED WITH MEMORY ITEMS FOR SMOKE AND THE CAPT DESELECTED THE APU GENERATOR. SMOKE IMMEDIATELY STOPPED AND DISSIPATED. WE REQUESTED DELAYING VECTORS AND COMPLETED SMOKE AND ELECTRICAL SMOKE QRC/QRH PROCS. ABOUT 5 MINS AFTER THE SMOKE CLRED; WE HAD A BLUE STATUS CAS R PACK FAIL. I WAS UNABLE TO RESET THE PACK SUCCESSFULLY AND WE RETURNED TO THE FIELD WITH BOTH PACKS; BLEEDS AND APU BLEED SELECTED OFF. THE LNDG WAS NORMAL; THE ACFT WAS SEARCHED BY FIREMEN AFTER THE PAX WERE DEPLANED AT THE GATE. NO SMOKE ENTERED OR WAS EVIDENT IN THE CABIN BECAUSE OF THE HEAT EXCHANGER FAN DEFERRAL.