Air carrier had near midair collision with an unknown opposite direction aircraft.

Attributes
ACN	126252
Time
Date	198910
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : bos
State Reference	MA
Altitude	msl bound lower : 12400 msl bound upper : 12600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	departure other
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	None
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 5
ASRS Report	126252
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : nmac non adherence : far other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action none taken : detected after the fact
Consequence	Other
Miss Distance	horizontal : 0 vertical : 200
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

I am an fpl radar controller at ZBW. I was working at sector 18 in a 1 hole confign. I was getting busy, so I asked the area supervisor for help at approximately XA31Z. At approximately XA35Z, air carrier X reported that an aircraft passed about 200' overhead. I observed an aircraft at that moment on a VFR code, opp direction of air carrier X. I told the pilot that I had not seen the aircraft prior to his reporting it. I also noted that air carrier X descended a couple hundred ft to avoid the VFR. I later notified air carrier X when the traffic was no longer a factor. At approximately XA37Z, a manual controller arrived at sector 18 to assist me. C/a never initiated to bring my attention to the possible conflict. One holing a sector causes distrs that may possibly have diverted my attention. Help not arriving in a timely manner added to workload for me. This incident was reported to the area supervisor.

Original NASA ASRS Text

Title: ACR HAD NMAC WITH AN UNKNOWN OPPOSITE DIRECTION ACFT.

Narrative: I AM AN FPL RADAR CTLR AT ZBW. I WAS WORKING AT SECTOR 18 IN A 1 HOLE CONFIGN. I WAS GETTING BUSY, SO I ASKED THE AREA SUPVR FOR HELP AT APPROX XA31Z. AT APPROX XA35Z, ACR X RPTED THAT AN ACFT PASSED ABOUT 200' OVERHEAD. I OBSERVED AN ACFT AT THAT MOMENT ON A VFR CODE, OPP DIRECTION OF ACR X. I TOLD THE PLT THAT I HAD NOT SEEN THE ACFT PRIOR TO HIS RPTING IT. I ALSO NOTED THAT ACR X DSNDED A COUPLE HUNDRED FT TO AVOID THE VFR. I LATER NOTIFIED ACR X WHEN THE TFC WAS NO LONGER A FACTOR. AT APPROX XA37Z, A MANUAL CTLR ARRIVED AT SECTOR 18 TO ASSIST ME. C/A NEVER INITIATED TO BRING MY ATTN TO THE POSSIBLE CONFLICT. ONE HOLING A SECTOR CAUSES DISTRS THAT MAY POSSIBLY HAVE DIVERTED MY ATTN. HELP NOT ARRIVING IN A TIMELY MANNER ADDED TO WORKLOAD FOR ME. THIS INCIDENT WAS RPTED TO THE AREA SUPVR.

Data retrieved from NASA's ASRS site as of August 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.