3 piper small transport aircraft departing the same airport in close proximity to each other requesting IFR clrncs caused controller confusion. The controller mistakenly cleared the second small transport to climb through the altitude of the first small transport. Less than standard separation between aircraft resulted.

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Attributes
ACN	361526
Time
Date	199702
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : loz
State Reference	KY
Altitude	msl bound lower : 8300 msl bound upper : 8300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid
Make Model Name	PA-31T Cheyenne II
Operating Under FAR Part	other : unknown
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Aircraft 2
Make Model Name	PA-31T Cheyenne II
Operating Under FAR Part	other : unknown
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 6
ASRS Report	361256
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	none taken : detected after the fact
Consequence	Other
Miss Distance	horizontal : 18000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Small transport X called on frequency requesting clearance from loz to dts. I gave small transport X a transponder code. A few seconds later small transport Y called on frequency requesting clearance from loz to dts. I gave small transport Y a transponder code. I called small transport X back in radar contact and cleared him to dts climb to FL200. A third paye departed loz requesting clearance to gad and I gave him a transponder code. I called small transport Y back to squawk the code again and gave clearance to dts maintain 7000 ft. He said they were through 8400 ft. I expedited him through 9000 ft to 11000 ft. When small transport Y called on after small transport X I assumed small transport Y departed after small transport X and was at a lower altitude. When small transport Y was given clearance, he and small transport X were climbing through 8300 ft, 3 mi apart. As a controller, I failed to check both aircraft's altitudes before giving the second clearance.

Original NASA ASRS Text

Title: 3 PIPER SMT ACFT DEPARTING THE SAME ARPT IN CLOSE PROX TO EACH OTHER REQUESTING IFR CLRNCS CAUSED CTLR CONFUSION. THE CTLR MISTAKENLY CLRED THE SECOND SMT TO CLB THROUGH THE ALT OF THE FIRST SMT. LTSS BTWN ACFT RESULTED.

Narrative: SMT X CALLED ON FREQ REQUESTING CLRNC FROM LOZ TO DTS. I GAVE SMT X A XPONDER CODE. A FEW SECONDS LATER SMT Y CALLED ON FREQ REQUESTING CLRNC FROM LOZ TO DTS. I GAVE SMT Y A XPONDER CODE. I CALLED SMT X BACK IN RADAR CONTACT AND CLRED HIM TO DTS CLB TO FL200. A THIRD PAYE DEPARTED LOZ REQUESTING CLRNC TO GAD AND I GAVE HIM A XPONDER CODE. I CALLED SMT Y BACK TO SQUAWK THE CODE AGAIN AND GAVE CLRNC TO DTS MAINTAIN 7000 FT. HE SAID THEY WERE THROUGH 8400 FT. I EXPEDITED HIM THROUGH 9000 FT TO 11000 FT. WHEN SMT Y CALLED ON AFTER SMT X I ASSUMED SMT Y DEPARTED AFTER SMT X AND WAS AT A LOWER ALT. WHEN SMT Y WAS GIVEN CLRNC, HE AND SMT X WERE CLBING THROUGH 8300 FT, 3 MI APART. AS A CTLR, I FAILED TO CHK BOTH ACFT'S ALTS BEFORE GIVING THE SECOND CLRNC.

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.