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A B757's TCASII senses a descending aircraft above and commands the crew to descend out of FL250, avoiding a B737 in a rapid descent to FL260.
| Attributes | |
| ACN | 429390 |
| Time | |
| Date | 199902 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | navaid : ric.vortac |
| State Reference | VA |
| Altitude | msl bound lower : 24300 msl bound upper : 25000 |
| Environment | |
| Flight Conditions | IMC |
| Weather Elements | other |
| Light | Dusk |
| Aircraft 1 | |
| Controlling Facilities | artcc : zdc.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B757-200 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other other vortac |
| Flight Phase | cruise : level |
| Route In Use | arrival star : ns enroute airway : ns.airway |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zdc.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other vortac |
| Flight Phase | cruise : enroute altitude change |
| Route In Use | arrival star : ns enroute airway : ns.airway |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : multi engine pilot : instrument pilot : atp pilot : commercial pilot : flight engineer |
| Experience | flight time last 90 days : 110 flight time total : 6800 flight time type : 1200 |
| ASRS Report | 429396 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp pilot : commercial pilot : flight engineer pilot : multi engine |
| Experience | flight time last 90 days : 180 flight time total : 9500 flight time type : 1000 |
| ASRS Report | 429391 |
| Events | |
| Anomaly | conflict : airborne less severe non adherence other other anomaly other |
| Independent Detector | aircraft equipment : tcas other flight crewa |
| Resolutory Action | controller : issued new clearance controller : issued advisory flight crew : took evasive action |
| Miss Distance | horizontal : 0 vertical : 1500 |
| Supplementary | |
| Problem Areas | Aircraft Flight Crew Human Performance ATC Human Performance |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | other |
Narrative:
Near ric, approaching dca for landing, ATC called us to say they had lost our mode C. As he called, we got a TCASII TA, followed immediately by an RA to 'descend.' TCASII screen showed traffic right above us, descending through about FL265. We initiated a 1200 FPM descent. RA stopped at about FL245. Leveled at FL243. Advised ATC of TCASII RA descent. ATC assigned us FL240, then communicated with other air carrier and asked if they were leveling FL260. They said they were. Believe we got RA because of rapid descent of same direction flight right above us. ATC may have lost our mode C because of our identical position and tracks. No further communications about the situation. Supplemental information from acn 429391: ZDC began transmitting to us that he had lost our mode C and then continued talking about traffic in the area. We attempted to broadcast our actions to center, but were unable because he was still talking. Flight conditions were dusk, IMC with no opportunity for a visual acquisition of traffic.
Original NASA ASRS Text
Title: A B757'S TCASII SENSES A DSNDING ACFT ABOVE AND COMMANDS THE CREW TO DSND OUT OF FL250, AVOIDING A B737 IN A RAPID DSCNT TO FL260.
Narrative: NEAR RIC, APCHING DCA FOR LNDG, ATC CALLED US TO SAY THEY HAD LOST OUR MODE C. AS HE CALLED, WE GOT A TCASII TA, FOLLOWED IMMEDIATELY BY AN RA TO 'DSND.' TCASII SCREEN SHOWED TFC RIGHT ABOVE US, DSNDING THROUGH ABOUT FL265. WE INITIATED A 1200 FPM DSCNT. RA STOPPED AT ABOUT FL245. LEVELED AT FL243. ADVISED ATC OF TCASII RA DSCNT. ATC ASSIGNED US FL240, THEN COMMUNICATED WITH OTHER ACR AND ASKED IF THEY WERE LEVELING FL260. THEY SAID THEY WERE. BELIEVE WE GOT RA BECAUSE OF RAPID DSCNT OF SAME DIRECTION FLT RIGHT ABOVE US. ATC MAY HAVE LOST OUR MODE C BECAUSE OF OUR IDENTICAL POS AND TRACKS. NO FURTHER COMS ABOUT THE SIT. SUPPLEMENTAL INFO FROM ACN 429391: ZDC BEGAN XMITTING TO US THAT HE HAD LOST OUR MODE C AND THEN CONTINUED TALKING ABOUT TFC IN THE AREA. WE ATTEMPTED TO BROADCAST OUR ACTIONS TO CTR, BUT WERE UNABLE BECAUSE HE WAS STILL TALKING. FLT CONDITIONS WERE DUSK, IMC WITH NO OPPORTUNITY FOR A VISUAL ACQUISITION OF TFC.
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.