Atx descended to an altitude that conflicted with another aircraft.

Attributes
ACN	121450
Time
Date	198909
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : hfd
State Reference	CT
Altitude	msl bound lower : 13000 msl bound upper : 13000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zbw
Operator	common carrier : air taxi
Make Model Name	Medium Transport, Low Wing, 2 Turboprop Eng
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
ASRS Report	121450
Person 2
Affiliation	company : air taxi
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : instrument pilot : commercial
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	Other
Miss Distance	horizontal : 18000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Pilot missed the readback on an altitude assigned (initially) then, controller assigned wrong altitude on second issuance of an altitude.

Original NASA ASRS Text

Title: ATX DESCENDED TO AN ALT THAT CONFLICTED WITH ANOTHER ACFT.

Narrative: PLT MISSED THE READBACK ON AN ALT ASSIGNED (INITIALLY) THEN, CTLR ASSIGNED WRONG ALT ON SECOND ISSUANCE OF AN ALT.

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.