Narrative:

We were air carrier flight abc from lga to ord. We followed an air carrier fokker on departure from runway 31. An air carrier B727 was immediately behind us for runway 31. Our initial clearance was 5000 ft and heading 360 degrees. Approaching 5000 ft ATC cleared us to 11000 ft. At approximately 6000 ft ATC cleared us to level at 8000 ft turn 310 degree heading. After leveling at 8000 ft, 310 degree heading, our TCASII advised of an aircraft behind at 7 O'clock position at 7000 ft climbing. At TCASII indication of aircraft at 7500 ft climbing we responding to initial resolution to climb. At 8200 ft, our altitude, the traffic was at 7800 ft climbing on our TCASII. The controller cleared us to 9000 ft upon our notification of climbing for resolution. He immediately directed a turn to 330 degree heading. The air carrier B727 was then visually acquired at our 8 O'clock position approximately 1 NM away. The controller then queried us 'why did you turn off of the 360 degree heading?' our reply 'we were told to turn to 310 degree heading.' the incident was concluded and we were passed off to another ATC frequency where declared our intent to file a near midair report. Supplemental information from acn 427466: I was training a developmental atcs on lga departure while departing runway 31 with 340 degree and 360 degree heading assigned by lga tower depending on their departure SID (fix). The trainee restr a B737 jet and a B727 jet, consecutive departures on 360 degree and 340 degree headings respectively, to 8000 ft because of wbound crossing traffic at 9000 ft. The trainee turned the first departure to a 310 degree heading approximately 8 mi north of lga, this heading consequently brought the B737 jet on a crossing or converging heading with the second departure the B727 jet on a 360 degree heading. The third departure came off on a 360 degree heading, a fokker jet, and the trainee had no flight data strip. He and I must have become distracted and I (the trainer) missed the '310 degree heading' transmission given to the B737 jet moments earlier. I noticed the track of the B737 jet and B727 jet converging and instructed the B737 jet to turn north and the B727 jet to turn wbound to increase the separation. I believe we became (trainer and trainee) distracted with the missing information. I don't recall hearing the trainee turn the B737 jet or the B727 jets. Readback, however, it was clear on the tape. There was no background interference at the time nor were we very busy. This was just human error!

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Original NASA ASRS Text

Title: B737 AND B727 HAD LESS THAN LEGAL SEPARATION.

Narrative: WE WERE ACR FLT ABC FROM LGA TO ORD. WE FOLLOWED AN ACR FOKKER ON DEP FROM RWY 31. AN ACR B727 WAS IMMEDIATELY BEHIND US FOR RWY 31. OUR INITIAL CLRNC WAS 5000 FT AND HDG 360 DEGS. APCHING 5000 FT ATC CLRED US TO 11000 FT. AT APPROX 6000 FT ATC CLRED US TO LEVEL AT 8000 FT TURN 310 DEG HDG. AFTER LEVELING AT 8000 FT, 310 DEG HDG, OUR TCASII ADVISED OF AN ACFT BEHIND AT 7 O'CLOCK POS AT 7000 FT CLBING. AT TCASII INDICATION OF ACFT AT 7500 FT CLBING WE RESPONDING TO INITIAL RESOLUTION TO CLB. AT 8200 FT, OUR ALT, THE TFC WAS AT 7800 FT CLBING ON OUR TCASII. THE CTLR CLRED US TO 9000 FT UPON OUR NOTIFICATION OF CLBING FOR RESOLUTION. HE IMMEDIATELY DIRECTED A TURN TO 330 DEG HDG. THE ACR B727 WAS THEN VISUALLY ACQUIRED AT OUR 8 O'CLOCK POS APPROX 1 NM AWAY. THE CTLR THEN QUERIED US 'WHY DID YOU TURN OFF OF THE 360 DEG HDG?' OUR REPLY 'WE WERE TOLD TO TURN TO 310 DEG HDG.' THE INCIDENT WAS CONCLUDED AND WE WERE PASSED OFF TO ANOTHER ATC FREQ WHERE DECLARED OUR INTENT TO FILE A NEAR MIDAIR RPT. SUPPLEMENTAL INFO FROM ACN 427466: I WAS TRAINING A DEVELOPMENTAL ATCS ON LGA DEP WHILE DEPARTING RWY 31 WITH 340 DEG AND 360 DEG HDG ASSIGNED BY LGA TWR DEPENDING ON THEIR DEP SID (FIX). THE TRAINEE RESTR A B737 JET AND A B727 JET, CONSECUTIVE DEPS ON 360 DEG AND 340 DEG HDGS RESPECTIVELY, TO 8000 FT BECAUSE OF WBOUND XING TFC AT 9000 FT. THE TRAINEE TURNED THE FIRST DEP TO A 310 DEG HDG APPROX 8 MI N OF LGA, THIS HEADING CONSEQUENTLY BROUGHT THE B737 JET ON A XING OR CONVERGING HEADING WITH THE SECOND DEP THE B727 JET ON A 360 DEG HDG. THE THIRD DEP CAME OFF ON A 360 DEG HDG, A FOKKER JET, AND THE TRAINEE HAD NO FLT DATA STRIP. HE AND I MUST HAVE BECOME DISTRACTED AND I (THE TRAINER) MISSED THE '310 DEG HDG' XMISSION GIVEN TO THE B737 JET MOMENTS EARLIER. I NOTICED THE TRACK OF THE B737 JET AND B727 JET CONVERGING AND INSTRUCTED THE B737 JET TO TURN N AND THE B727 JET TO TURN WBOUND TO INCREASE THE SEPARATION. I BELIEVE WE BECAME (TRAINER AND TRAINEE) DISTRACTED WITH THE MISSING INFO. I DON'T RECALL HEARING THE TRAINEE TURN THE B737 JET OR THE B727 JETS. READBACK, HOWEVER, IT WAS CLR ON THE TAPE. THERE WAS NO BACKGROUND INTERFERENCE AT THE TIME NOR WERE WE VERY BUSY. THIS WAS JUST HUMAN ERROR!

Data retrieved from NASA's ASRS site as of July 2007 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.