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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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An medium large transport indicates 300 ft off altitude in ZAU airspace. Transponder is at fault, giving a false altitude to ARTCC.
| Attributes | |
| ACN | 373670 |
| Time | |
| Date | 199707 |
| Day | Thu |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : bae |
| State Reference | WI |
| Altitude | msl bound lower : 27700 msl bound upper : 29000 |
| Environment | |
| Flight Conditions | VMC |
| 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 | cruise other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 210 flight time total : 6800 flight time type : 1000 |
| ASRS Report | 373670 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : far |
| Independent Detector | atc equipment other atc equipment : unspecified other controllera |
| Resolutory Action | flight crew : overcame equipment problem |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
ZAU cleared our flight to climb to 28000 ft. Prior to climbing the controller advised that our mode C was indicating 280/300 ft low. We changed altitude encoder and climbed to 29000 ft. At cruise we worked with the controller to test the original encoder. It then appeared to have failed as the controller advised that it was not reporting altitude. The unit was written up and reported to our maintenance department.
Original NASA ASRS Text
Title: AN MLG INDICATES 300 FT OFF ALT IN ZAU AIRSPACE. XPONDER IS AT FAULT, GIVING A FALSE ALT TO ARTCC.
Narrative: ZAU CLRED OUR FLT TO CLB TO 28000 FT. PRIOR TO CLBING THE CTLR ADVISED THAT OUR MODE C WAS INDICATING 280/300 FT LOW. WE CHANGED ALT ENCODER AND CLBED TO 29000 FT. AT CRUISE WE WORKED WITH THE CTLR TO TEST THE ORIGINAL ENCODER. IT THEN APPEARED TO HAVE FAILED AS THE CTLR ADVISED THAT IT WAS NOT RPTING ALT. THE UNIT WAS WRITTEN UP AND RPTED TO OUR MAINT DEPT.
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.