ZID radar controller lost separation between descending and en route aircraft.

Attributes
ACN	579311
Time
Date	200304
Day	Fri
Local Time Of Day	0601 To 1200
Place
State Reference	WV
Altitude	msl bound lower : 28000 msl bound upper : 33000
Environment
Weather Elements	Turbulence
Light	Night
Aircraft 1
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	B727-200
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zid.artcc
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 13
ASRS Report	579311
Person 2
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment : conflict alert other controllera
Resolutory Action	none taken : detected after the fact
Consequence	faa : investigated
Miss Distance	horizontal : 21000 vertical : 200
Supplementary
Problem Areas	Maintenance Human Performance ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Aircraft #1 was at FL330. Descent clearance issued to FL290. Due to extreme noise and commotion in area from maintenance to facility equipment, and lack of radar associate available, pilot read back FL240, and that reply was missed. Descended through altitude of aircraft #2.

Original NASA ASRS Text

Title: ZID RADAR CTLR LOST SEPARATION BTWN DSNDING AND ENRTE ACFT.

Narrative: ACFT #1 WAS AT FL330. DSCNT CLRNC ISSUED TO FL290. DUE TO EXTREME NOISE AND COMMOTION IN AREA FROM MAINT TO FACILITY EQUIP, AND LACK OF RADAR ASSOCIATE AVAILABLE, PLT READ BACK FL240, AND THAT REPLY WAS MISSED. DSNDED THROUGH ALT OF ACFT #2.

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.