Premier 1
Air Traffic Control Fully Certified
Communication Breakdown; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance
Human Factors; Procedure
BWI was in a west operation; landing Runway 33L/R. A Premier was descended to 2;000 on a 210 degree heading approximately 7 miles northeast of BWI. The Premier called the airport in sight and was cleared for a visual \approach to Runway 33R and instructed to contact BWI Tower. A Citation was being vectored to Runway 33L; approximately 5 miles to the southeast of the Premier. I turned the Citation to a 270 degree heading; but immediately noticed the Premier had not commenced a base to final turn; and changed the Citation's heading to 250 degrees. I called BWI Tower and alerted them that the Premier should have been turning base to final. BWI Tower replied that they would instruct the Premier to turn in. I had descended the Citation to 2;000 turned them onto the Runway 33L localizer and at the same time called the opposite runway traffic. The Premier never turned onto the Runway 33R final and continued not only across the Runway 33R final; but the Runway 33L final as well. I immediately climbed the Citation to 2;500 to avoid a collision; after which the Citation reported traffic insight. The Premier was able to turn back towards the airport and land; whereas I vectored the Citation around for a subsequent visual approach and landing. BWI Tower could have been more proactive by noticing the Premier was not flying a pattern consistent with a landing on Runway 33R.
PCT Controller described a conflict event occurring after an aircraft was cleared for a visual approach on base; but failed to turn toward the airport to the correct runway.