Pilot readback clearance for another aircraft which resulted in less than standard separation.

Attributes
ACN	146586
Time
Date	199005
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : aml
State Reference	VA
Altitude	msl bound lower : 20000 msl bound upper : 22000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	general aviation : corporate
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	climbout : intermediate altitude cruise other
Flight Plan	IFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Small Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller military : 5 controller radar : 3
ASRS Report	146586
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 24600 vertical : 6
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error Pilot Deviation

Narrative:

Aircraft a level at FL200 on a photo mission. Aircraft B swbnd level at FL220 in potential conflict with photo mission aircraft C, climbing to interim altitude of FL190 requesting FL200 as a final. Aircraft B call sign: small transport xy; aircraft C call sign: small transport Y. Small transport xy given clearance to climb to FL220. Small transport Y at FL190 westbound is observed climbing out of FL190. Small transport Y told to descend back down to FL190. Small transport Y mistakenly read back the clearance to climb by saying, 'Y, roger.' did not use full or abbreviated call sign. Frequency not clear enough to distinguish between phonetics of 'Y' and 'xy.'

Original NASA ASRS Text

Title: PLT READBACK CLRNC FOR ANOTHER ACFT WHICH RESULTED IN LESS THAN STANDARD SEPARATION.

Narrative: ACFT A LEVEL AT FL200 ON A PHOTO MISSION. ACFT B SWBND LEVEL AT FL220 IN POTENTIAL CONFLICT WITH PHOTO MISSION ACFT C, CLBING TO INTERIM ALT OF FL190 REQUESTING FL200 AS A FINAL. ACFT B CALL SIGN: SMT XY; ACFT C CALL SIGN: SMT Y. SMT XY GIVEN CLRNC TO CLB TO FL220. SMT Y AT FL190 WBND IS OBSERVED CLBING OUT OF FL190. SMT Y TOLD TO DSND BACK DOWN TO FL190. SMT Y MISTAKENLY READ BACK THE CLRNC TO CLB BY SAYING, 'Y, ROGER.' DID NOT USE FULL OR ABBREVIATED CALL SIGN. FREQ NOT CLR ENOUGH TO DISTINGUISH BTWN PHONETICS OF 'Y' AND 'XY.'

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.