A90 CTLR AND MD83 PLT DESCRIBE NIGHT VISUAL SEPARATION INCIDENT WITH ARR AT 6000 FT AND DEP CLBING FROM 5000 FT.

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LJ35 DEPARTING BOS CLBING TO 5000 FT HDG 120 DEGS. MD83 DOWNWIND RWY 33L; HDG 150 DEGS. MD83 AND LJ35 ISSUED TFC; BOTH HAVE EACH OTHER IN SIGHT. LJ35 STATES HE HAS THE MD83 IN SIGHT AND WILL PROVIDE VISUAL SEPARATION. VISUAL SEPARATION IS APPROVED AND LJ35 ISSUED A CLB TO 14000 FT. MD83 IS NOTIFIED LJ35 IS APPLYING VISUAL SEPARATION AND WILL BE CLBING TO THE NE. MD83 STATED HE SAW LJ35 WELL IN ADVANCE AND THAT THE PLT OF LJ35 WAS LYING WHEN HE STATED HE HAD MD83 IN SIGHT. LJ35 STATED BOTH CREW MEMBERS HAD THE MD83 IN SIGHT AND WERE VERY FAMILIAR WITH VISUAL SEPARATION PROCS. MD83 STATED THE ACFT CAME WITHIN 300 FT VERT. LJ35 STATED THEY WERE 1000 FT BENEATH THE MD83. RADAR DATA SAYS 500 FT AND 1/10 MILE CLOSEST POINT. MD83 SAID IT WAS THE CLOSEST THING HE EVER SAW AND HE FLEW MANY HIGH SPD MIL MISSIONS. HE FILED AN NMAC RPT AND SOUNDED SHAKEN UP. HE MISTAKENLY MADE A 160 DEG R TURN AFTER THE INCIDENT APPARENTLY DUE TO HIS RESPONSE TO THE EVENT (STRESS/CONFUSION). ALL THIS HAPPENED AT NIGHT; VFR CONDITIONS; AND EXCELLENT VISIBILITY. TWO EXPERIENCED FLT CREWS BOTH HAD VASTLY DIFFERENT RECALL OF THE SAME EVENT. FOR ONE; IT WAS NORMAL; THE OTHER; AN EMER. NIGHT AND FATIGUE MAY BE FACTORS. MD83 STARTED TO ARGUE ON FREQ CALLING THE OTHER PLT A LIAR AND HIS REPLY; 'BOGUS.' THIS IS NOT THE PLACE FOR ARGUMENT. MD83 FORGOT TO FLY THE PLANE AFTER THE EVENT AND EXECUTED A TURN WHEN NONE WAS ISSUED; MISTAKENLY THINKING HE WAS GIVEN A BASE TURN. NIGHT DISTANCES ARE DIFFICULT TO JUDGE. STAYING WITH STANDARD SEPARATION AND RADAR SVC IS A BETTER WAY TO DO BUSINESS. SUPPLEMENTAL INFO FROM ACN 669257: ON A HDG OF ABOUT 150 DEGS ON DOWNWIND FOR RWY 33L BOS; AN ACFT DEPARTED RWY 15 AND WAS CLRED TO CLB TO 5000 FT. WE WERE LEVEL AT 6000 FT. THE ACFT WAS ABEAM US ON CLB OUT. CTR ASKED IF HE HAD US IN SIGHT. HE SAID HE DID THEN ATC CLRED HIM TO TURN N AND CLB TO 14000 FT AND MAINTAIN VISUAL SEPARATION WITH US. HE THEN TURNED DIRECTLY TOWARD US AND CLBED. OUR TCAS CALLED OUT TFC THEN MAINTAIN VERT SPD. THE TCAS READ 300 FT BELOW US AS THE ACFT PASSED DIRECTLY BELOW US. IT ALSO APPEARED TO BE 200 TO 300 FT BELOW US FROM THE FO WINDOW. AFTER THE ACFT HAD PASSED; ATC GAVE US A TURN TO THE R. WE THEN TURNED ABOUT 30 DEGS BEYOND THE HDG BECAUSE WE WERE RPTING THE PRIOR INCIDENT. ATC TOLD US TO TURN BACK TO OUR HDG. WE DID.