Less than standard separation between 2 aircraft in holding pattern at same altitude.

Attributes
ACN	85432
Time
Date	198804
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : den
State Reference	CO
Altitude	msl bound lower : 16000 msl bound upper : 16100
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv tower : den
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 7
ASRS Report	85432
Person 2
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance none taken : insufficient time
Consequence	faa : investigated
Miss Distance	horizontal : 18600 vertical : 100
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Medium large transport X and small transport Y were holding and waiting to land denver. I was the relieving controller and it is my contention that small transport Y was cleared inbound to land den, from the briefing I received. Small transport Y was descended from 17000 to 16000' to land den. Medium large transport X was cleared inbound to den, nebnd. Small transport Y reached the holding fix and turned swbnd. Realizing small transport Y was not cleared inbound, I turned both aircraft but could not maintain sep. Medium large transport X inbound at 16000' was issued an immediate left turn and small transport Y an immediate right turn.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN 2 ACFT IN HOLDING PATTERN AT SAME ALT.

Narrative: MLG X AND SMT Y WERE HOLDING AND WAITING TO LAND DENVER. I WAS THE RELIEVING CTLR AND IT IS MY CONTENTION THAT SMT Y WAS CLRED INBND TO LAND DEN, FROM THE BRIEFING I RECEIVED. SMT Y WAS DSNDED FROM 17000 TO 16000' TO LAND DEN. MLG X WAS CLRED INBND TO DEN, NEBND. SMT Y REACHED THE HOLDING FIX AND TURNED SWBND. REALIZING SMT Y WAS NOT CLRED INBND, I TURNED BOTH ACFT BUT COULD NOT MAINTAIN SEP. MLG X INBND AT 16000' WAS ISSUED AN IMMEDIATE LEFT TURN AND SMT Y AN IMMEDIATE RIGHT TURN.

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.