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Mode C swap air carrier X TCASII false traffic air carrier Y shown 500 ft below. No RA issued by TCASII.
| Attributes | |
| ACN | 285209 |
| Time | |
| Date | 199410 |
| Day | Fri |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : pll |
| State Reference | IL |
| Altitude | msl bound lower : 10000 msl bound upper : 10000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | ATR 42 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise other |
| Route In Use | enroute : direct enroute airway : zau |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Beech 1900 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | climbout : intermediate altitude |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Experience | controller radar : 6 |
| ASRS Report | 285209 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : unspecified other controllera |
| Resolutory Action | none taken : anomaly accepted |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
Air carrier X, an ATR-42, in level flight at 10000 ft on a converging course with air carrier Y, a be-02, climbing out of 5100 for 7000 ft. On the radar scope, the beacon targets were in close proximity causing a mode C swap, showing both aircraft at 9500 ft. X was TCASII equipped and asked if I showed traffic immediately under them at 9500 ft. I advised of the known air carrier Y traffic and my observation of the mode C swap. The pilot of X advised that TCASII showed traffic at 9500 ft but disappeared during our conversation. This is my first experience with a mode C swap appearing on my radar scope and having a TCASII equipped aircraft report the swap showing up as traffic on their TCASII. No RA's were issued and no deviations effected.
Original NASA ASRS Text
Title: MODE C SWAP ACR X TCASII FALSE TFC ACR Y SHOWN 500 FT BELOW. NO RA ISSUED BY TCASII.
Narrative: ACR X, AN ATR-42, IN LEVEL FLT AT 10000 FT ON A CONVERGING COURSE WITH ACR Y, A BE-02, CLBING OUT OF 5100 FOR 7000 FT. ON THE RADAR SCOPE, THE BEACON TARGETS WERE IN CLOSE PROX CAUSING A MODE C SWAP, SHOWING BOTH ACFT AT 9500 FT. X WAS TCASII EQUIPPED AND ASKED IF I SHOWED TFC IMMEDIATELY UNDER THEM AT 9500 FT. I ADVISED OF THE KNOWN ACR Y TFC AND MY OBSERVATION OF THE MODE C SWAP. THE PLT OF X ADVISED THAT TCASII SHOWED TFC AT 9500 FT BUT DISAPPEARED DURING OUR CONVERSATION. THIS IS MY FIRST EXPERIENCE WITH A MODE C SWAP APPEARING ON MY RADAR SCOPE AND HAVING A TCASII EQUIPPED ACFT RPT THE SWAP SHOWING UP AS TFC ON THEIR TCASII. NO RA'S WERE ISSUED AND NO DEVS EFFECTED.
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.