Military X climb through occupied altitude had less than standard separation from military Y TCASII....

Attributes
ACN	297573
Time
Date	199502
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ilm
State Reference	NC
Altitude	msl bound lower : 21000 msl bound upper : 21000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	other
Make Model Name	Eagle (F-15)
Operating Under FAR Part	other : other
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	other
Make Model Name	Military Transport
Operating Under FAR Part	other : other
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 non radar : 2 controller radar : 1
ASRS Report	297573
Person 2
Affiliation	government : military
Function	flight crew : single pilot
Qualification	pilot : military
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 other flight crewa
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated faa : reviewed incident with flight crew
Miss Distance	horizontal : 2500 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation Operational Error

Narrative:

At approximately xa UTC, military X checked on my frequency climbing to 10000 ft. I issued a clearance to 16000 ft at approximately xxxxc I thought I issued a clearance to climb to FL200, the requested altitude of X. Military Y a C26 at FL210 nebound on J121 was issued a TA on X climbing to FL200. Y stated he had the traffic on TCASII a few min later, the conflict alert flashed for X and Y. I noticed X mode C readout indicated FL203. I asked X to verify assigned altitude of FL200. X reported that his assigned altitude was FL220. I then issued a clearance to X to FL200, moments later I issued a clearance to FL220 since X and Y had passed in opposite directions and were separated by more than 5 mi. I believe confusion related to the similar sounding altitudes of FL200 and FL220 caused the problem.

Original NASA ASRS Text

Title: MIL X CLB THROUGH OCCUPIED ALT HAD LTSS FROM MIL Y TCASII. SYS ERROR.

Narrative: AT APPROX XA UTC, MIL X CHKED ON MY FREQ CLBING TO 10000 FT. I ISSUED A CLRNC TO 16000 FT AT APPROX XXXXC I THOUGHT I ISSUED A CLRNC TO CLB TO FL200, THE REQUESTED ALT OF X. MIL Y A C26 AT FL210 NEBOUND ON J121 WAS ISSUED A TA ON X CLBING TO FL200. Y STATED HE HAD THE TFC ON TCASII A FEW MIN LATER, THE CONFLICT ALERT FLASHED FOR X AND Y. I NOTICED X MODE C READOUT INDICATED FL203. I ASKED X TO VERIFY ASSIGNED ALT OF FL200. X RPTED THAT HIS ASSIGNED ALT WAS FL220. I THEN ISSUED A CLRNC TO X TO FL200, MOMENTS LATER I ISSUED A CLRNC TO FL220 SINCE X AND Y HAD PASSED IN OPPOSITE DIRECTIONS AND WERE SEPARATED BY MORE THAN 5 MI. I BELIEVE CONFUSION RELATED TO THE SIMILAR SOUNDING ALTS OF FL200 AND FL220 CAUSED THE PROB.

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.

Military X climb through occupied altitude had less than standard separation from military Y TCASII. System error.