Less than standard separation between 2 GA aircraft. Operational error.

Attributes
ACN	105487
Time
Date	198902
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : spw
State Reference	IA
Altitude	msl bound lower : 5600 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other descent other
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller military : 2 controller non radar : 2 controller radar : 10
ASRS Report	105487
Person 2
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance none taken : insufficient time
Consequence	faa : investigated
Miss Distance	horizontal : 9000 vertical : 400
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Intra Facility Coordination Failure Operational Error
Situations
ATC Facility	procedure or policy : unspecified

Narrative:

I relieved sector 10 radar and data positions. Proper relief briefing was initiated, but apparently distracted by aircraft X calling. He was VFR 5500' asking for clearance. Controller leaving told me about aircraft Y at 6000', but I lost awareness of him. Aircraft Y was non radar and X was radar contact. There was some confusion over the spencer altimeter setting. My first notice of aircraft Y was a limited data block 10 O'clock, 10 mi from X. Because I didn't believe there was any other traffic in the area, I believed the limited data block to be a split beacon from aircraft X. Both strips were in the bay, but I had a mental block and only seemed to process one. I called the traffic to aircraft X, and even told him that the traffic may not be real. He acknowledged traffic in sight, and that is when I realized there was something amiss. I made a blanket broadcast for traffic in the spencer area. I then noticed the strip on aircraft Y. I issued X an immediate descent to 5000'. Traffic missed by 1-2 mi and 500'. Initial reaction to this system error is lack of controller awareness, however there is more at stake here. I feel that the #1 cause of this incident is lack of familiarity with the sector in question and low altitude in general. This all boils down to the implementation of the high/low concept and the problems it has caused since its inception. I & most of my fellow controllers are not able to make adjustments to the dramatic differences between working traffic in high and working traffic in low.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN 2 GA ACFT. OPERATIONAL ERROR.

Narrative: I RELIEVED SECTOR 10 RADAR AND DATA POSITIONS. PROPER RELIEF BRIEFING WAS INITIATED, BUT APPARENTLY DISTRACTED BY ACFT X CALLING. HE WAS VFR 5500' ASKING FOR CLRNC. CTLR LEAVING TOLD ME ABOUT ACFT Y AT 6000', BUT I LOST AWARENESS OF HIM. ACFT Y WAS NON RADAR AND X WAS RADAR CONTACT. THERE WAS SOME CONFUSION OVER THE SPENCER ALTIMETER SETTING. MY FIRST NOTICE OF ACFT Y WAS A LIMITED DATA BLOCK 10 O'CLOCK, 10 MI FROM X. BECAUSE I DIDN'T BELIEVE THERE WAS ANY OTHER TFC IN THE AREA, I BELIEVED THE LIMITED DATA BLOCK TO BE A SPLIT BEACON FROM ACFT X. BOTH STRIPS WERE IN THE BAY, BUT I HAD A MENTAL BLOCK AND ONLY SEEMED TO PROCESS ONE. I CALLED THE TFC TO ACFT X, AND EVEN TOLD HIM THAT THE TFC MAY NOT BE REAL. HE ACKNOWLEDGED TFC IN SIGHT, AND THAT IS WHEN I REALIZED THERE WAS SOMETHING AMISS. I MADE A BLANKET BROADCAST FOR TFC IN THE SPENCER AREA. I THEN NOTICED THE STRIP ON ACFT Y. I ISSUED X AN IMMEDIATE DSCNT TO 5000'. TFC MISSED BY 1-2 MI AND 500'. INITIAL REACTION TO THIS SYS ERROR IS LACK OF CTLR AWARENESS, HOWEVER THERE IS MORE AT STAKE HERE. I FEEL THAT THE #1 CAUSE OF THIS INCIDENT IS LACK OF FAMILIARITY WITH THE SECTOR IN QUESTION AND LOW ALT IN GENERAL. THIS ALL BOILS DOWN TO THE IMPLEMENTATION OF THE HIGH/LOW CONCEPT AND THE PROBS IT HAS CAUSED SINCE ITS INCEPTION. I & MOST OF MY FELLOW CTLRS ARE NOT ABLE TO MAKE ADJUSTMENTS TO THE DRAMATIC DIFFERENCES BTWN WORKING TFC IN HIGH AND WORKING TFC IN LOW.

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.