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Mode C readout on an air carrier goes to 999 for one sweep of the radar antenna, and another target on an air carrier goes into coast status for two sweeps.
| Attributes | |
| ACN | 230308 |
| Time | |
| Date | 199301 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : tpa |
| State Reference | FL |
| Altitude | msl bound lower : 3000 msl bound upper : 3000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | tracon : tpa |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Navigation In Use | Other |
| Flight Phase | descent other |
| Route In Use | arrival other |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 3 Turbojet Eng |
| Flight Phase | descent other |
| Route In Use | arrival other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : approach |
| Qualification | controller : radar |
| Experience | controller radar : 10 |
| ASRS Report | 230308 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | other anomaly other |
| Independent Detector | other controllera |
| Resolutory Action | none taken : unable |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Navigational Facility |
| Air Traffic Incident | other |
| Situations | |
| Navigational Aid | Unspecified |
Narrative:
While working the final position at tpa I noticed two erroneous mode C readouts. The first one was on air carrier X on the tpa 002/7.69. I observed the mode C to be 999 for 1 sweep and then the aircraft went into CST for 1 sweep. The aircraft was in a descent when this occurred. This aircraft was around 3000 ft descending when this occurred. The second occurrence was with air carrier Y on the tpa 018/15.19 descending through 6000 ft. This aircraft was observed to be in a CST status for 2 sweeps.
Original NASA ASRS Text
Title: MODE C READOUT ON AN ACR GOES TO 999 FOR ONE SWEEP OF THE RADAR ANTENNA, AND ANOTHER TARGET ON AN ACR GOES INTO COAST STATUS FOR TWO SWEEPS.
Narrative: WHILE WORKING THE FINAL POS AT TPA I NOTICED TWO ERRONEOUS MODE C READOUTS. THE FIRST ONE WAS ON ACR X ON THE TPA 002/7.69. I OBSERVED THE MODE C TO BE 999 FOR 1 SWEEP AND THEN THE ACFT WENT INTO CST FOR 1 SWEEP. THE ACFT WAS IN A DSCNT WHEN THIS OCCURRED. THIS ACFT WAS AROUND 3000 FT DSNDING WHEN THIS OCCURRED. THE SECOND OCCURRENCE WAS WITH ACR Y ON THE TPA 018/15.19 DSNDING THROUGH 6000 FT. THIS ACFT WAS OBSERVED TO BE IN A CST STATUS FOR 2 SWEEPS.
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.