ATC mix-up on assigned altitude causes less than legal separation.

Attributes
ACN	236573
Time
Date	199303
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ott
State Reference	MD
Altitude	msl bound lower : 18000 msl bound upper : 19000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	general aviation : corporate
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Operator	other
Make Model Name	Military Transport
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : instrument pilot : cfi pilot : atp
Experience	flight time last 90 days : 90 flight time total : 3100 flight time type : 1400
ASRS Report	236573
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 9000 flight time type : 3500
ASRS Report	236516
Events
Anomaly	altitude deviation : overshoot non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 18000
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

While descending through FL180 the controller came on and asked what our altitude was. We replied FL180 for 11000 ft. The controller then issued a right turn to 150 degrees (approximately 70 degrees right). The controller told us to level at 17000 ft and said mlt traffic had passed at FL180 3 mi away. They understood we were to stop at FL190 and we replied that we were told to cross 65 southwest of nottingham (ott) at 11000 ft. The controller said it must have been their fault. The controller had called out traffic previously and I believe he meant to tell us to level at FL190 and forgot. Supplemental information from acn 236516: my first officer had written the clearance back on the radio.

Original NASA ASRS Text

Title: ATC MIX-UP ON ASSIGNED ALT CAUSES LESS THAN LEGAL SEPARATION.

Narrative: WHILE DSNDING THROUGH FL180 THE CTLR CAME ON AND ASKED WHAT OUR ALT WAS. WE REPLIED FL180 FOR 11000 FT. THE CTLR THEN ISSUED A R TURN TO 150 DEGS (APPROX 70 DEGS R). THE CTLR TOLD US TO LEVEL AT 17000 FT AND SAID MLT TFC HAD PASSED AT FL180 3 MI AWAY. THEY UNDERSTOOD WE WERE TO STOP AT FL190 AND WE REPLIED THAT WE WERE TOLD TO CROSS 65 SW OF NOTTINGHAM (OTT) AT 11000 FT. THE CTLR SAID IT MUST HAVE BEEN THEIR FAULT. THE CTLR HAD CALLED OUT TFC PREVIOUSLY AND I BELIEVE HE MEANT TO TELL US TO LEVEL AT FL190 AND FORGOT. SUPPLEMENTAL INFO FROM ACN 236516: MY FO HAD WRITTEN THE CLRNC BACK ON THE RADIO.

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.