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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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Transponder mode C altitude readout questionable. Reporter believes that ATC equipment was reading in error because no other ATC facility had questioned their altitude throughout a long cross country flight.
| Attributes | |
| ACN | 346490 |
| Time | |
| Date | 199609 |
| Day | Wed |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : mtu |
| State Reference | UT |
| Altitude | msl bound lower : 19000 msl bound upper : 20000 |
| Aircraft 1 | |
| Controlling Facilities | artcc : zlc |
| Operator | common carrier : air carrier |
| Make Model Name | Fokker 100 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | descent other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| ASRS Report | 346490 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument |
| Events | |
| Anomaly | aircraft equipment problem : less severe other anomaly other |
| Independent Detector | other controllera |
| Resolutory Action | none taken : unable other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | other |
Narrative:
ATC questioned us once as to what was our mode C around FL250 descending to cross spane at FL190 then again around FL200 for FL190. According to our equipment, we crossed spane at FL190. This was the first time in the long leg that any ATC inquiry was made. I believe that it was his equipment in error, thus I did not think an E-6 entry was warranted.
Original NASA ASRS Text
Title: XPONDER MODE C ALT READOUT QUESTIONABLE. RPTR BELIEVES THAT ATC EQUIP WAS READING IN ERROR BECAUSE NO OTHER ATC FACILITY HAD QUESTIONED THEIR ALT THROUGHOUT A LONG XCOUNTRY FLT.
Narrative: ATC QUESTIONED US ONCE AS TO WHAT WAS OUR MODE C AROUND FL250 DSNDING TO CROSS SPANE AT FL190 THEN AGAIN AROUND FL200 FOR FL190. ACCORDING TO OUR EQUIP, WE CROSSED SPANE AT FL190. THIS WAS THE FIRST TIME IN THE LONG LEG THAT ANY ATC INQUIRY WAS MADE. I BELIEVE THAT IT WAS HIS EQUIP IN ERROR, THUS I DID NOT THINK AN E-6 ENTRY WAS WARRANTED.
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.