Military fgt Y same altitude assigned had less than standard separation from fgt Z. System error.

Attributes
ACN	224846
Time
Date	199210
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : btl
State Reference	MI
Altitude	msl bound lower : 4000 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : azo
Operator	other
Make Model Name	Fighter
Flight Phase	descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	other
Make Model Name	Fighter
Flight Phase	descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 20 controller supervisory : 13
ASRS Report	224846
Person 2
Affiliation	government : military
Function	flight crew : single pilot
Qualification	pilot : military
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	none taken : detected after the fact
Consequence	faa : investigated
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was vectoring a flight of 3 fgts into btl airport for individual ILS approachs. I work at azo approach control, which controls the approachs into btl airport. On initial contact, the fgts requested a split-up for individual ILS approachs at btl and land. Flight lead X requested that Z go in first followed by Y and last, the leader. A split was started. I gave Z and Y transponder codes and instructed them to squawk. They (the xponders) did not come on and I could not see the primary targets. I had other crossing traffic and it was very important to have a display so I could rely on radar's separation and not altitude reports. This was a very unusual situation and rattled me pretty good. Another factor is that the flight was doing 330 KTS ground speed at 9000 ft (surface wind calm). After the split-up and during vectors for individual approachs, I misjudged the tracks and fgts Z and Y came between 1 to 2 mi apart, and the ARTS ii conflict alert went off. Azo ASR has had a terrible maintenance record -- the radar performance is marginal.

Original NASA ASRS Text

Title: MIL FGT Y SAME ALT ASSIGNED HAD LTSS FROM FGT Z. SYS ERROR.

Narrative: I WAS VECTORING A FLT OF 3 FGTS INTO BTL ARPT FOR INDIVIDUAL ILS APCHS. I WORK AT AZO APCH CTL, WHICH CTLS THE APCHS INTO BTL ARPT. ON INITIAL CONTACT, THE FGTS REQUESTED A SPLIT-UP FOR INDIVIDUAL ILS APCHS AT BTL AND LAND. FLT LEAD X REQUESTED THAT Z GO IN FIRST FOLLOWED BY Y AND LAST, THE LEADER. A SPLIT WAS STARTED. I GAVE Z AND Y XPONDER CODES AND INSTRUCTED THEM TO SQUAWK. THEY (THE XPONDERS) DID NOT COME ON AND I COULD NOT SEE THE PRIMARY TARGETS. I HAD OTHER XING TFC AND IT WAS VERY IMPORTANT TO HAVE A DISPLAY SO I COULD RELY ON RADAR'S SEPARATION AND NOT ALT RPTS. THIS WAS A VERY UNUSUAL SIT AND RATTLED ME PRETTY GOOD. ANOTHER FACTOR IS THAT THE FLT WAS DOING 330 KTS GND SPD AT 9000 FT (SURFACE WIND CALM). AFTER THE SPLIT-UP AND DURING VECTORS FOR INDIVIDUAL APCHS, I MISJUDGED THE TRACKS AND FGTS Z AND Y CAME BTWN 1 TO 2 MI APART, AND THE ARTS II CONFLICT ALERT WENT OFF. AZO ASR HAS HAD A TERRIBLE MAINT RECORD -- THE RADAR PERFORMANCE IS MARGINAL.

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.