Aircraft descended through altitude of another aircraft.

Attributes
ACN	106570
Time
Date	198903
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ihd
State Reference	PA
Altitude	msl bound lower : 12000 msl bound upper : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : direct enroute airway : zob
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 15
ASRS Report	106570
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	none taken : anomaly accepted
Consequence	faa : investigated
Miss Distance	horizontal : 22200 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X inbound to pit via ths ihd V474 nesto pit was given a descent clearance to 13000' due to small transport Y en route ths V474 ihd at 12000'. Air carrier X read back 10000' but I did not catch this due to sector workload at the time, ie, inbound pit rush with approximately 15-20 aircraft in sector at time. Also air carrier B was north sector at this time and was given a clearance to 10000' prior to this. Air carrier X was at 12200' when I caught this and C/a went off also at this time.

Original NASA ASRS Text

Title: ACFT DESCENDED THROUGH ALT OF ANOTHER ACFT.

Narrative: ACR X INBND TO PIT VIA THS IHD V474 NESTO PIT WAS GIVEN A DSCNT CLRNC TO 13000' DUE TO SMT Y ENRTE THS V474 IHD AT 12000'. ACR X READ BACK 10000' BUT I DID NOT CATCH THIS DUE TO SECTOR WORKLOAD AT THE TIME, IE, INBND PIT RUSH WITH APPROX 15-20 ACFT IN SECTOR AT TIME. ALSO ACR B WAS N SECTOR AT THIS TIME AND WAS GIVEN A CLRNC TO 10000' PRIOR TO THIS. ACR X WAS AT 12200' WHEN I CAUGHT THIS AND C/A WENT OFF ALSO AT THIS TIME.

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.