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C90 controller described direct altimeter setting indicator (dasi) anomaly that resulted in false altitude information being displayed.
| Attributes | |
| ACN | 794358 |
| Time | |
| Date | 200807 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : c90.tracon |
| State Reference | IL |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : departure |
| Qualification | controller : radar |
| Experience | controller military : 3 controller radar : 23 |
| ASRS Report | 794358 |
| Events | |
| Independent Detector | other controllera |
| Resolutory Action | none taken : anomaly accepted |
| Supplementary | |
| Problem Areas | FAA Navigational Facility |
| Primary Problem | Navigational Facility |
Narrative:
Jul/xa/08; the dasi for ord changed inexplicably to an incorrect reading. This sudden change caused the mode C readout to change by approximately 1000 ft. Not a good thing with all of the traffic C90 has in its airspace. I think we need to find out exactly why this happened. Guesses are unacceptable. Proposed solution: after the exact problem is discovered; fix it so that it doesn't happen again.
Original NASA ASRS Text
Title: C90 CTLR DESCRIBED DIRECT ALTIMETER SETTING INDICATOR (DASI) ANOMALY THAT RESULTED IN FALSE ALT INFO BEING DISPLAYED.
Narrative: JUL/XA/08; THE DASI FOR ORD CHANGED INEXPLICABLY TO AN INCORRECT READING. THIS SUDDEN CHANGE CAUSED THE MODE C READOUT TO CHANGE BY APPROX 1000 FT. NOT A GOOD THING WITH ALL OF THE TFC C90 HAS IN ITS AIRSPACE. I THINK WE NEED TO FIND OUT EXACTLY WHY THIS HAPPENED. GUESSES ARE UNACCEPTABLE. PROPOSED SOLUTION: AFTER THE EXACT PROB IS DISCOVERED; FIX IT SO THAT IT DOESN'T HAPPEN AGAIN.
Data retrieved from NASA's ASRS site as of May 2009 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.