Air Traffic Control Fully Certified
Confusion; Communication Breakdown
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance
Human Factors
A Heavy was inbound from the southwest to Runway 6. An MD80 was inbound from the northwest to Runway 6. The Heavy was number one; while the MD80 was about 7-10 miles in trail; but the Heavy said he needed a 360 to loose more altitude for the approach. I turned the Heavy right to a 090 heading off of the approach to let the MD80 be number one. I then turned the Heavy again right to 330 heading. I meant to turn the Heavy to a 150 heading (a 330 heading is the opposite heading for the base turn for Runway 6). I noticed my mistake when the Heavy went through the 150 heading; I thought I had given him; when he was on an approximate 220 heading. I then said fly heading 150. While expecting the Heavy to turn back left to a 150 heading; because of the approximate 220 heading he was on; he kept going right to a 150 heading which made him a factor with the MD80. If the Heavy had turned back left to a 150 heading like he was supposed to it would have been no factor. However; when he continued the right turn it appeared separation could have been lost with the MD80. I was able to get the Heavy to turn left to a 150 heading and very well could have had divergence. [Do] not use 'fly heading'; but actually use 'turn left/right heading' most of the time.
TRACON Controller described a loss of separation event when using the phrase 'fly headings' in lieu of the more precise 'turn left/right etc' resulting in the conflict.