TRACON controller described a loss of separation event when using the phrase 'fly headings' in lieu ...

Narrative:

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.

Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1084879
Time
Date	201305
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Heavy Transport
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Approach Departure
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Conflict Airborne Conflict Deviation - Procedural Published Material / Policy

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.