Cpr Y had less than standard separation from air carrier X. System error.

Attributes
ACN	166518
Time
Date	199012
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lfd
State Reference	MI
Altitude	msl bound lower : 31000 msl bound upper : 33000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 4 controller radar : 2
ASRS Report	166518
Person 2
Affiliation	government : faa
Function	controller : flight data
Qualification	controller : radar
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 15600 vertical : 1100
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X was eastbound at FL330, cpr Y was westbound at FL310 requesting FL350. Cpr Y was cleared direct to fsd and when reinstating the altitude to maintain, the controller inadvertently said FL350 instead of FL310. The controller was aware of the traffic at FL330 and did not mean to say FL350. Neither controller (radar or assistant) caught the error before sep was lost, and cpr Y was descended to FL310. The closest proximity was 2.6 mi and 1100'. This incident shows, I believe, that human errors will happen and that most of the time they get caught but sometimes they get by everyone.

Original NASA ASRS Text

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

Narrative: ACR X WAS EBND AT FL330, CPR Y WAS WBND AT FL310 REQUESTING FL350. CPR Y WAS CLRED DIRECT TO FSD AND WHEN REINSTATING THE ALT TO MAINTAIN, THE CTLR INADVERTENTLY SAID FL350 INSTEAD OF FL310. THE CTLR WAS AWARE OF THE TFC AT FL330 AND DID NOT MEAN TO SAY FL350. NEITHER CTLR (RADAR OR ASSISTANT) CAUGHT THE ERROR BEFORE SEP WAS LOST, AND CPR Y WAS DSNDED TO FL310. THE CLOSEST PROX WAS 2.6 MI AND 1100'. THIS INCIDENT SHOWS, I BELIEVE, THAT HUMAN ERRORS WILL HAPPEN AND THAT MOST OF THE TIME THEY GET CAUGHT BUT SOMETIMES THEY GET BY EVERYONE.

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.