An air carrier flight crew deviated from an assigned altitude as a result of clearance confusion.

Attributes
ACN	300987
Time
Date	199503
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mdw
State Reference	IL
Altitude	msl bound lower : 12000 msl bound upper : 12500
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 10000 flight time type : 240
ASRS Report	300987
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : private pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 240 flight time total : 2800 flight time type : 900
ASRS Report	300610
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Climbing out of chicago with center 133.5. Captain flying and first officer was off of radio. 12000 ft was last altitude. Approaching 12000 ft captain heard climb to FL310. Out of 12500 ft center asked assigned altitude. We went back to 12000 ft. Center said no problem. Supplemental information from acn 300610: upon returning to VHF #1 I caught the last part of a call for us. Some confusion arose if we were cleared to FL310. Occurred as we passed 13500 ft center asked for our altitude. We started a descent back to 12000 ft. Center then cleared us to 13000 ft with a frequency change.

Original NASA ASRS Text

Title: AN ACR FLC DEVIATED FROM AN ASSIGNED ALT AS A RESULT OF CLRNC CONFUSION.

Narrative: CLBING OUT OF CHICAGO WITH CTR 133.5. CAPT FLYING AND FO WAS OFF OF RADIO. 12000 FT WAS LAST ALT. APCHING 12000 FT CAPT HEARD CLB TO FL310. OUT OF 12500 FT CTR ASKED ASSIGNED ALT. WE WENT BACK TO 12000 FT. CTR SAID NO PROB. SUPPLEMENTAL INFO FROM ACN 300610: UPON RETURNING TO VHF #1 I CAUGHT THE LAST PART OF A CALL FOR US. SOME CONFUSION AROSE IF WE WERE CLRED TO FL310. OCCURRED AS WE PASSED 13500 FT CTR ASKED FOR OUR ALT. WE STARTED A DSCNT BACK TO 12000 FT. CTR THEN CLRED US TO 13000 FT WITH A FREQ CHANGE.

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.