Altitude deviation on descent.

Attributes
ACN	299631
Time
Date	199503
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : bdf airport : ord
State Reference	IL
Altitude	msl bound lower : 10000 msl bound upper : 11000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
ASRS Report	299632
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	299631
Events
Anomaly	altitude deviation : overshoot inflight encounter : weather non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	flight crew : became reoriented flight crew : returned to intended course or assigned course other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation
Situations
ATC Facility	procedure or policy : unspecified

Narrative:

We received a clearance at FL270 to descend to cross benky intersection at 11000 ft. We thought the altimeter given by ZAU was 30.34. We had not yet copied that ATIS or received the changeover. We were handed off to approach control and leveled at 11000 ft. Approach told us to maintain 11000 ft. The captain answered that we were level at 11000 ft. Approach replied that they showed us at 10000 ft, altimeter 29.34. We reset our altimeters and climbed back to 11000 ft. No traffic conflict was mentioned by ATC, nor did we observe any, either visually or on TCASII.

Original NASA ASRS Text

Title: ALTDEV ON DSCNT.

Narrative: WE RECEIVED A CLRNC AT FL270 TO DSND TO CROSS BENKY INTXN AT 11000 FT. WE THOUGHT THE ALTIMETER GIVEN BY ZAU WAS 30.34. WE HAD NOT YET COPIED THAT ATIS OR RECEIVED THE CHANGEOVER. WE WERE HANDED OFF TO APCH CTL AND LEVELED AT 11000 FT. APCH TOLD US TO MAINTAIN 11000 FT. THE CAPT ANSWERED THAT WE WERE LEVEL AT 11000 FT. APCH REPLIED THAT THEY SHOWED US AT 10000 FT, ALTIMETER 29.34. WE RESET OUR ALTIMETERS AND CLBED BACK TO 11000 FT. NO TFC CONFLICT WAS MENTIONED BY ATC, NOR DID WE OBSERVE ANY, EITHER VISUALLY OR ON TCASII.

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.