Cleared descend to 20000, thought cleared to 11000 ft, got TCASII.

Attributes
ACN	220150
Time
Date	199209
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : uin
State Reference	IL
Altitude	msl bound lower : 19500 msl bound upper : 20000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zkc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 5000 flight time type : 1300
ASRS Report	220150
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : required legal separation non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : took evasive action other
Consequence	Other
Miss Distance	horizontal : 18000 vertical : 700
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were cleared to descend to FL200 with clearance to cross bramr at 350 KTS and 11000 ft. Passing FL195 center asked our altitude and we got a TCASII alert. We leveled off at FL195, then center cleared us down to 11000 ft/250 KTS at bramr. We thought our clearance was to 11000 ft and it was to FL200 expect 11000 ft. We had the traffic visually and maintained separation. We had a breakdown in communication caused by not thoroughly understanding the clearance. Approaching FL207 for level off alarm went off and the captain reset 11000 ft. At that point I should have challenged him.

Original NASA ASRS Text

Title: CLRED DSND TO 20000, THOUGHT CLRED TO 11000 FT, GOT TCASII.

Narrative: WE WERE CLRED TO DSND TO FL200 WITH CLRNC TO CROSS BRAMR AT 350 KTS AND 11000 FT. PASSING FL195 CTR ASKED OUR ALT AND WE GOT A TCASII ALERT. WE LEVELED OFF AT FL195, THEN CTR CLRED US DOWN TO 11000 FT/250 KTS AT BRAMR. WE THOUGHT OUR CLRNC WAS TO 11000 FT AND IT WAS TO FL200 EXPECT 11000 FT. WE HAD THE TFC VISUALLY AND MAINTAINED SEPARATION. WE HAD A BREAKDOWN IN COM CAUSED BY NOT THOROUGHLY UNDERSTANDING THE CLRNC. APCHING FL207 FOR LEVEL OFF ALARM WENT OFF AND THE CAPT RESET 11000 FT. AT THAT POINT I SHOULD HAVE CHALLENGED HIM.

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.