An incorrect altimeter setting results in descent below assigned altitude during arrival at ord.

Attributes
ACN	602070
Time
Date	200312
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : ord.airport
State Reference	IL
Altitude	msl bound lower : 6000 msl bound upper : 7000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : c90.tracon tower : bos.tower
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : multi engine
ASRS Report	602070
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	altitude deviation : overshoot inflight encounter other non adherence : far non adherence : clearance
Independent Detector	other controllerb
Resolutory Action	controller : issued advisory flight crew : returned to assigned altitude flight crew : became reoriented
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance Weather ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

South of ord 50 NM. On descent into ord, ZAU issued us further descent to 7000 ft while passing FL190, the altimeter setting and a frequency change. We think that the controller may have given us an incorrect altimeter setting, 30.27 instead of 29.27 for landing in ord. Regardless, the captain and I set 30.27 instead of the correct setting of 29.27. We continued to what we thought was 7000 ft for the leveloff. After reaching leveloff, the controller for the new frequency we had been given told us to climb to 7000 ft. I responded that we were level at 7000 ft. He told us the altimeter setting and we corrected it, and climbed to the 'correct' altitude. After leveling at 7000 ft I asked the controller if there was any problem and he responded that there was not. The captain and I talked about it after we arrived at the gate and decided that in the future, it would be better to compare the controller's altimeter setting to what we received from the airport ATIS on the ACARS printout. If there seems to be a discrepancy, ask the controller for clarification.

Original NASA ASRS Text

Title: AN INCORRECT ALTIMETER SETTING RESULTS IN DSCNT BELOW ASSIGNED ALT DURING ARR AT ORD.

Narrative: S OF ORD 50 NM. ON DSCNT INTO ORD, ZAU ISSUED US FURTHER DSCNT TO 7000 FT WHILE PASSING FL190, THE ALTIMETER SETTING AND A FREQ CHANGE. WE THINK THAT THE CTLR MAY HAVE GIVEN US AN INCORRECT ALTIMETER SETTING, 30.27 INSTEAD OF 29.27 FOR LNDG IN ORD. REGARDLESS, THE CAPT AND I SET 30.27 INSTEAD OF THE CORRECT SETTING OF 29.27. WE CONTINUED TO WHAT WE THOUGHT WAS 7000 FT FOR THE LEVELOFF. AFTER REACHING LEVELOFF, THE CTLR FOR THE NEW FREQ WE HAD BEEN GIVEN TOLD US TO CLB TO 7000 FT. I RESPONDED THAT WE WERE LEVEL AT 7000 FT. HE TOLD US THE ALTIMETER SETTING AND WE CORRECTED IT, AND CLBED TO THE 'CORRECT' ALT. AFTER LEVELING AT 7000 FT I ASKED THE CTLR IF THERE WAS ANY PROB AND HE RESPONDED THAT THERE WAS NOT. THE CAPT AND I TALKED ABOUT IT AFTER WE ARRIVED AT THE GATE AND DECIDED THAT IN THE FUTURE, IT WOULD BE BETTER TO COMPARE THE CTLR'S ALTIMETER SETTING TO WHAT WE RECEIVED FROM THE ARPT ATIS ON THE ACARS PRINTOUT. IF THERE SEEMS TO BE A DISCREPANCY, ASK THE CTLR FOR CLARIFICATION.

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.