ZDC controller does not ensure vertical separation between 2 descending air carrier aircraft.

Attributes
ACN	453549
Time
Date	199910
Day	Fri
Local Time Of Day	1201 To 1800
Place
State Reference	VA
Altitude	msl single value : 13000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc.artcc
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zdc.artcc
Operator	common carrier : air carrier
Make Model Name	Dash 8-100
Operating Under FAR Part	Part 121
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	government : faa other
Function	controller : radar instruction : instructor
Qualification	controller : radar
Experience	controller military : 6 controller radar : 9
ASRS Report	453549
Person 2
Affiliation	government : faa other
Function	controller : radar instruction : trainee
Qualification	controller : developmental
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : radar
Resolutory Action	controller : issued advisory
Consequence	faa : reviewed incident with flight crew faa : investigated
Miss Distance	horizontal : 20800 vertical : 0
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I observed air carrier X descending out of 13000 ft. Air carrier Y was at 13000 ft. I asked air carrier X to verify assigned altitude. He said 12000 ft and asked if I wanted him to climb back up. I told him to maintain 12000 ft since he was already through air carrier Y's altitude.

Original NASA ASRS Text

Title: ZDC CTLR DOES NOT ENSURE VERT SEPARATION BTWN 2 DSNDING ACR ACFT.

Narrative: I OBSERVED ACR X DSNDING OUT OF 13000 FT. ACR Y WAS AT 13000 FT. I ASKED ACR X TO VERIFY ASSIGNED ALT. HE SAID 12000 FT AND ASKED IF I WANTED HIM TO CLB BACK UP. I TOLD HIM TO MAINTAIN 12000 FT SINCE HE WAS ALREADY THROUGH ACR Y'S ALT.

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.