Cpr X was descended through air carrier Y's altitude. Less than standard separation. System error.

Attributes
ACN	122448
Time
Date	198909
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : dfw
State Reference	TX
Altitude	msl bound lower : 5000 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : dfw
Operator	general aviation : corporate
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
ASRS Report	122448
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : developmental
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	other controllera
Resolutory Action	none taken : detected after the fact
Consequence	faa : investigated
Miss Distance	unspecified : 0 vertical : 6000
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

A cpr X inbound from the northeast at 7000' was turned to 230 degrees and descended to 5000'. Below the cpr X was an air carrier Y at 6000' on the 215 degree right of buj VOR. A deviation controller (trnee) was working with a journeyman controller (me) conducting OJT. The traffic was moderate. I had not heard the trnee descend the cpr X and only became aware when I noticed the mode C readout showing the cpr X somewhere around 6000' the tags were overlapping and the close proximity of xponders did not allow for continuous mode C readout. The trnee later stated he did not see the air carrier Y at the time he issued the clearance. The air carrier Y had not yet checked in from ZFW, but was well inside dfw approach controls airspace (10 mi). Suggestions for prevention: 1) pay greater attention to trnee's xmissions and pilot's readback; 2) if the air carrier Y had checked in sooner, the trnee may have realized his presence. A prompt frequency change from the center may have helped.

Original NASA ASRS Text

Title: CPR X WAS DESCENDED THROUGH ACR Y'S ALT. LESS THAN STANDARD SEPARATION. SYSTEM ERROR.

Narrative: A CPR X INBND FROM THE NE AT 7000' WAS TURNED TO 230 DEGS AND DSNDED TO 5000'. BELOW THE CPR X WAS AN ACR Y AT 6000' ON THE 215 DEG R OF BUJ VOR. A DEV CTLR (TRNEE) WAS WORKING WITH A JOURNEYMAN CTLR (ME) CONDUCTING OJT. THE TFC WAS MODERATE. I HAD NOT HEARD THE TRNEE DSND THE CPR X AND ONLY BECAME AWARE WHEN I NOTICED THE MODE C READOUT SHOWING THE CPR X SOMEWHERE AROUND 6000' THE TAGS WERE OVERLAPPING AND THE CLOSE PROX OF XPONDERS DID NOT ALLOW FOR CONTINUOUS MODE C READOUT. THE TRNEE LATER STATED HE DID NOT SEE THE ACR Y AT THE TIME HE ISSUED THE CLRNC. THE ACR Y HAD NOT YET CHKED IN FROM ZFW, BUT WAS WELL INSIDE DFW APCH CTLS AIRSPACE (10 MI). SUGGESTIONS FOR PREVENTION: 1) PAY GREATER ATTN TO TRNEE'S XMISSIONS AND PLT'S READBACK; 2) IF THE ACR Y HAD CHKED IN SOONER, THE TRNEE MAY HAVE REALIZED HIS PRESENCE. A PROMPT FREQ CHANGE FROM THE CENTER MAY HAVE HELPED.

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.