IMC cpr Y had near midair collision with VMC small transport X. See and avoid concept.

Attributes
ACN	165822
Time
Date	199012
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : gso
State Reference	NC
Altitude	msl bound lower : 12000 msl bound upper : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl
Operator	general aviation : personal
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	descent other
Flight Plan	VFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
ASRS Report	165822
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument
Events
Anomaly	conflict : nmac
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 400 vertical : 0
Supplementary
Primary Problem	Flight Crew Human Performance

Narrative:

This event involved small transport X at 13000' from cje to buy and cpr Y at 12000' from 4w8 to cha. I was the radar controller at sector 29 at atlanta center. Small transport X checked in at FL130 requesting lower. I cleared small transport X to turn left to heading 065 for descent, about a 60 degree turn. Small transport X immediately cancelled IFR due to the sector complexity at the time, I terminated small transport X and did not offer advisories. Shortly after I turned cpr Y on course, (he was on a heading for traffic). Although I didn't recognize it at the time, this in effect put small transport X and cpr Y head on to each other. I first noticed the conflict when the aircraft were about 10 mi apart. Small transport X, now squawking VFR and off frequency was at 12800' descending. Cpr Y was level at 12000'. I called traffic to cpr Y approximately 3 times. Cpr Y never picked up the traffic. When I thought the aircraft were going to hit I suggested cpr Y turn 90 degrees right immediately. Cpr Y took the turn. The targets merged, both mode C readouts indicating 12000' at the time. Cpr Y never saw small transport X. Small transport X never called so I assume he didn't see cpr Y either.

Original NASA ASRS Text

Title: IMC CPR Y HAD NMAC WITH VMC SMT X. SEE AND AVOID CONCEPT.

Narrative: THIS EVENT INVOLVED SMT X AT 13000' FROM CJE TO BUY AND CPR Y AT 12000' FROM 4W8 TO CHA. I WAS THE RADAR CTLR AT SECTOR 29 AT ATLANTA CTR. SMT X CHKED IN AT FL130 REQUESTING LOWER. I CLRED SMT X TO TURN L TO HDG 065 FOR DSNT, ABOUT A 60 DEG TURN. SMT X IMMEDIATELY CANCELLED IFR DUE TO THE SECTOR COMPLEXITY AT THE TIME, I TERMINATED SMT X AND DID NOT OFFER ADVISORIES. SHORTLY AFTER I TURNED CPR Y ON COURSE, (HE WAS ON A HDG FOR TFC). ALTHOUGH I DIDN'T RECOGNIZE IT AT THE TIME, THIS IN EFFECT PUT SMT X AND CPR Y HEAD ON TO EACH OTHER. I FIRST NOTICED THE CONFLICT WHEN THE ACFT WERE ABOUT 10 MI APART. SMT X, NOW SQUAWKING VFR AND OFF FREQ WAS AT 12800' DSNDING. CPR Y WAS LEVEL AT 12000'. I CALLED TFC TO CPR Y APPROX 3 TIMES. CPR Y NEVER PICKED UP THE TFC. WHEN I THOUGHT THE ACFT WERE GOING TO HIT I SUGGESTED CPR Y TURN 90 DEGS R IMMEDIATELY. CPR Y TOOK THE TURN. THE TARGETS MERGED, BOTH MODE C READOUTS INDICATING 12000' AT THE TIME. CPR Y NEVER SAW SMT X. SMT X NEVER CALLED SO I ASSUME HE DIDN'T SEE CPR Y EITHER.

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.