Small transport X had less than standard separation from small transport Y. System error.

Attributes
ACN	140987
Time
Date	199003
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : msv
State Reference	NY
Altitude	msl bound lower : 1300 msl bound upper : 1300
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90 tower : mlb
Operator	general aviation : personal
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	climbout : initial climbout : intermediate altitude
Route In Use	departure other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 1 controller radar : 5
ASRS Report	140987
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	none taken : detected after the fact
Consequence	Other
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was working small transport X on approach ILS 15 at msv and forgot this aircraft. Small transport Y at msv called for clearance off msv. I issued the clearance and small transport Y departed (runway unknown, WX unknown). I realized the conflict after small transport Y reported leaving 2600' and small transport X called on the ground cancelling his IFR clearance simultaneously on 2 different frequencys. (Both were private aircraft.)

Original NASA ASRS Text

Title: SMT X HAD LESS THAN STANDARD SEPARATION FROM SMT Y. SYSTEM ERROR.

Narrative: I WAS WORKING SMT X ON APCH ILS 15 AT MSV AND FORGOT THIS ACFT. SMT Y AT MSV CALLED FOR CLRNC OFF MSV. I ISSUED THE CLRNC AND SMT Y DEPARTED (RWY UNKNOWN, WX UNKNOWN). I REALIZED THE CONFLICT AFTER SMT Y REPORTED LEAVING 2600' AND SMT X CALLED ON THE GND CANCELLING HIS IFR CLRNC SIMULTANEOUSLY ON 2 DIFFERENT FREQS. (BOTH WERE PRIVATE ACFT.)

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.