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Potential conflict when a B737 flight descends to the same altitude as opposite direction traffic as the clearance to FL250 was questioned by controller.
| Attributes | |
| ACN | 622354 |
| Time | |
| Date | 200310 |
| Day | Thu |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : zdc.artcc |
| State Reference | VA |
| Altitude | msl bound lower : 25000 msl bound upper : 27000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zdc.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : intermediate altitude |
| Route In Use | arrival star : korry |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zdc.artcc |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Experience | flight time last 90 days : 250 flight time total : 21000 flight time type : 7000 |
| ASRS Report | 622354 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : clearance non adherence : required legal separation |
| Independent Detector | atc equipment : conflict alert atc equipment other atc equipment : radar mode c aircraft equipment : tcas other controllera other flight crewa other flight crewb |
| Resolutory Action | none taken : detected after the fact |
| Consequence | faa : reviewed incident with flight crew |
| Miss Distance | horizontal : 27000 vertical : 0 |
| Supplementary | |
| Problem Areas | ATC Human Performance |
| Primary Problem | Ambiguous |
| Air Traffic Incident | Intra Facility Coordination Failure Operational Error |
Narrative:
I went bac to the lavatory before we began our descent on the orry arrival. We were at FL370. When I came bac. The captain briefed me on any changes which was, cleared to FL250. After several mins later, our TCASII gave a TA and we noticed traffic at our 1 O'cloc position, opposite direction at the same altitude and did pass off our right side about 4 or 5 mi. I thought this was strange and as I was about to question ZDC center about it, they ased us to state our altitude, which we did. They said we lost separation and that we should not be at that altitude but at FL270 and for us to give them a call. The captain explained that the previous controller cleared us to FL250 and that when he ched in he restated our altitude, FL250. About 5 mins later, ZDC told us that everything was O and we did not have to call them. We do not now what we could do different. My questions are, why did it tae over 5 mins before ATC questioned our altitude which involved 2 different controllers? Why did not their system project any conflicts when they cleared us or the other aircraft to that altitude?
Original NASA ASRS Text
Title: POTENTIAL CONFLICT WHEN A B737 FLT DSNDS TO THE SAME ALT AS OPPOSITE DIRECTION TFC AS THE CLRNC TO FL250 WAS QUESTIONED BY CTLR.
Narrative: I WENT BAC TO THE LAVATORY BEFORE WE BEGAN OUR DSCNT ON THE ORRY ARR. WE WERE AT FL370. WHEN I CAME BAC. THE CAPT BRIEFED ME ON ANY CHANGES WHICH WAS, CLRED TO FL250. AFTER SEVERAL MINS LATER, OUR TCASII GAVE A TA AND WE NOTICED TFC AT OUR 1 O'CLOC POS, OPPOSITE DIRECTION AT THE SAME ALT AND DID PASS OFF OUR R SIDE ABOUT 4 OR 5 MI. I THOUGHT THIS WAS STRANGE AND AS I WAS ABOUT TO QUESTION ZDC CTR ABOUT IT, THEY ASED US TO STATE OUR ALT, WHICH WE DID. THEY SAID WE LOST SEPARATION AND THAT WE SHOULD NOT BE AT THAT ALT BUT AT FL270 AND FOR US TO GIVE THEM A CALL. THE CAPT EXPLAINED THAT THE PREVIOUS CTLR CLRED US TO FL250 AND THAT WHEN HE CHED IN HE RESTATED OUR ALT, FL250. ABOUT 5 MINS LATER, ZDC TOLD US THAT EVERYTHING WAS O AND WE DID NOT HAVE TO CALL THEM. WE DO NOT NOW WHAT WE COULD DO DIFFERENT. MY QUESTIONS ARE, WHY DID IT TAE OVER 5 MINS BEFORE ATC QUESTIONED OUR ALT WHICH INVOLVED 2 DIFFERENT CTLRS? WHY DID NOT THEIR SYS PROJECT ANY CONFLICTS WHEN THEY CLRED US OR THE OTHER ACFT TO THAT ALT?
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.