AS THEY WERE TURNING OFF THE RWY AN ACR FLC SMELLED OIL AND SAW A SMOKY DISCHARGE FROM THEIR AIR-CONDITIONING VENTS AND THEY SHUT OFF THE AIR-CONDITIONING AND PRESSURIZATION SYS AND PERFORMED THE SMOKE EVAC CHKLIST. NO PAX EVAC WAS NECESSARY.

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WHILE TAXIING TO GATE; SMOKE ENTERED CABIN. I TOLD FO BLEED AIR OFF AND QUICK REACTION HANDBOOK SMOKE REMOVAL. SMOKE STOPPED AND WE GOT RID OF SMOKE. WE TAXIED BACK TO GATE AND NORMAL DEPLANED. NO EMER EVAC BECAUSE I ASKED FO TO CHK THE CABIN FOR SMOKE AND MAKE SURE PAX ARE OK AND HE TOLD ME ALL PAX ARE OK; BEHAVING NORMAL. NOTE: THIS IS MY 6TH SMOKE IN ACFT DUE TO A BAD COOLING TURBINE. MAYBE FAA NEEDS TO GET WITH THE PROGRAM AND ISSUE AN AIRWORTHINESS DIRECTIVE FOR THE METROLINER BEFORE WE GET ANOTHER ACR DISASTER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WAS FLYING A METROLINER SA227 WHEN HE SMELLED THE SCENT OF LUBRICATING OIL IN THE COCKPIT JUST AFTER TOUCHDOWN. HE SAID THAT HE KNEW THAT IT PROBABLY CAME FROM THE AIR CYCLE MACHINE IN THE AIR-CONDITIONING AND PRESSURIZATION UNIT SINCE HE HAS HAD 5 OR 6 SIMILAR EVENTS IN THIS ACFT. THE FO PERFORMED THE REQUIRED CHKLISTS AND THEY WERE ABLE TO VENT THE SMOKE WITH LITTLE DISTURBANCE FOR THE PAX. THE CAPT SAID THAT HE HAS TALKED TO THE COMPANY MAINT PERSONNEL; MGMNT AND THE MANUFACTURER'S TECHNICAL SUPPORT REPRESENTATIVE AND NOBODY SEEMS TO HAVE A SOLUTION FOR THIS CONTINUING PROB. THE RPTR SAID THAT SOME OF HIS SMOKE OCCURRENCES HAVE BEEN WORSE THAN THIS; BUT HE HAS NOT HAD AN EVAC YET. ANOTHER PROB WITH THE GENERAL DESIGN OF THE AIR- CONDITIONING AND PRESSURIZATION SYS IS THE LOCATION OF THE AIR INTAKE FOR THE AIR-CONDITIONING SYS BEING BEHIND THE CENTRAL FLUID DRAIN FOR THE ACFT. IN A PREVIOUS EVENT HE HAD EXPERIENCED A HYD SYS LOSS IN WHICH THE HYD FLUID DRAINED INTO THIS FLAMMABLE FLUID DRAIN; UNDER THE COCKPIT FLOOR; AND THEN WAS SUCKED UP BY THE AIR- CONDITIONING AIR INTAKE AND THEN INTO THE CABIN. THIS PROB DID RESULT IN AN EMER EVAC. THE RPTR ALLEGED THAT AFTER THIS LAST SMOKE/OIL EVENT THAT HE AND HIS FO AND A MAINT TECHNICIAN CONCLUDED THAT THE PROB WOULD NOT BE FIXED BECAUSE OF THE AGE OF THE ACFT UNLESS SOME NEW DESIGN COULD BE INEXPENSIVELY RETROFITTED. HE ALLEGED THAT THE MAINT TECHNICIAN DOUBTED THAT THIS DESIGN WOULD EVER BE LEAK PROOF.