Altitude deviation altitude overshot.

Attributes
ACN	203543
Time
Date	199203
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ord
State Reference	IL
Altitude	msl bound lower : 6700 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent : approach
Route In Use	approach : straight in enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 18000 flight time type : 11000
ASRS Report	203543
Person 2
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : instrument pilot : flight engineer pilot : atp pilot : commercial
Experience	flight time last 90 days : 50 flight time total : 3300 flight time type : 100
ASRS Report	203762
Events
Anomaly	altitude deviation : overshoot non adherence : published procedure 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:

Approach control to chicago O'hare advised us that our altitude reporting system was showing us approximately 300 ft below the actual altitude displayed on our center altimeter. The problem was reported to maintenance via radio and written log.

Original NASA ASRS Text

Title: ALTDEV ALT OVERSHOT.

Narrative: APCH CTL TO CHICAGO O'HARE ADVISED US THAT OUR ALT RPTING SYS WAS SHOWING US APPROX 300 FT BELOW THE ACTUAL ALT DISPLAYED ON OUR CTR ALTIMETER. THE PROBLEM WAS RPTED TO MAINT VIA RADIO AND WRITTEN LOG.

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.