Air carrier X had less than standard separation from small aircraft Y. System error.

Attributes
ACN	181227
Time
Date	199106
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : abe
State Reference	PA
Altitude	msl bound lower : 4000 msl bound upper : 4000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : abe tower : mgm
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : departure
Qualification	controller : radar
ASRS Report	181227
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I observed an aircraft on a beacon code of X 8 mi southeast of the abe airport. At the same time, I was vectoring air carrier X at 4000 ft, southwest en route from abe to bwi. I called the traffic out to air carrier X and turned him wbound to a heading of 270. I issued 2 more turns to air carrier X of 330 and 360 respectively. At the same time that air carrier X was turning northbound, the mode C of the 4000 ft aircraft indicated 2800 ft for 1 sweep of the radar. At this time I determined that the 4000 ft traffic was small aircraft Y assigned beacon code of Y, en route from pne to abe. I immediately issued the air carrier X traffic to small aircraft Y along with a left turn to 270. Small aircraft Y indicated that he had air carrier X in sight. I did accept the handoff from phl, but at some time after the handoff, small aircraft Y's beacon code had changed resulting in his data block being dropped from the radar scope. This occurred during an extremely busy period of traffic. I had to manually tag and when I was positive that he was no longer a conflict, I handed him off to the arrival radar position. I revectored air carrier X towards lrp and climbed him to 8000 ft. This situation most likely occurred as a result of an aircraft experiencing equipment problems during an extremely heavy traffic period. At this time, not knowing why small aircraft Y changed his beacon code, I cannot offer a suggestion on how to prevent this situation from recurring. It does, however, show the importance of why all pointed out aircraft should be tagged and all handed off aircraft shouldn't be dropped until they are well clear of one's airspace.

Original NASA ASRS Text

Title: ACR X HAD LTSS FROM SMA Y. SYSTEM ERROR.

Narrative: I OBSERVED AN ACFT ON A BEACON CODE OF X 8 MI SE OF THE ABE ARPT. AT THE SAME TIME, I WAS VECTORING ACR X AT 4000 FT, SW ENRTE FROM ABE TO BWI. I CALLED THE TFC OUT TO ACR X AND TURNED HIM WBOUND TO A HDG OF 270. I ISSUED 2 MORE TURNS TO ACR X OF 330 AND 360 RESPECTIVELY. AT THE SAME TIME THAT ACR X WAS TURNING NBOUND, THE MODE C OF THE 4000 FT ACFT INDICATED 2800 FT FOR 1 SWEEP OF THE RADAR. AT THIS TIME I DETERMINED THAT THE 4000 FT TFC WAS SMA Y ASSIGNED BEACON CODE OF Y, ENRTE FROM PNE TO ABE. I IMMEDIATELY ISSUED THE ACR X TFC TO SMA Y ALONG WITH A L TURN TO 270. SMA Y INDICATED THAT HE HAD ACR X IN SIGHT. I DID ACCEPT THE HDOF FROM PHL, BUT AT SOME TIME AFTER THE HDOF, SMA Y'S BEACON CODE HAD CHANGED RESULTING IN HIS DATA BLOCK BEING DROPPED FROM THE RADAR SCOPE. THIS OCCURRED DURING AN EXTREMELY BUSY PERIOD OF TFC. I HAD TO MANUALLY TAG AND WHEN I WAS POSITIVE THAT HE WAS NO LONGER A CONFLICT, I HANDED HIM OFF TO THE ARR RADAR POS. I REVECTORED ACR X TOWARDS LRP AND CLBED HIM TO 8000 FT. THIS SIT MOST LIKELY OCCURRED AS A RESULT OF AN ACFT EXPERIENCING EQUIP PROBS DURING AN EXTREMELY HVY TFC PERIOD. AT THIS TIME, NOT KNOWING WHY SMA Y CHANGED HIS BEACON CODE, I CANNOT OFFER A SUGGESTION ON HOW TO PREVENT THIS SIT FROM RECURRING. IT DOES, HOWEVER, SHOW THE IMPORTANCE OF WHY ALL POINTED OUT ACFT SHOULD BE TAGGED AND ALL HANDED OFF ACFT SHOULDN'T BE DROPPED UNTIL THEY ARE WELL CLR OF ONE'S AIRSPACE.

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.