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Operational error under ambiguous circumstances creates a potential conflict and loss of separation between two air carrier aircraft. Traffic and communication volume cited as contributory.
| Attributes | |
| ACN | 123910 |
| Time | |
| Date | 198909 |
| Day | Fri |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : ott |
| State Reference | MD |
| Altitude | msl bound lower : 12000 msl bound upper : 12000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zdc tracon : bwi tracon : dca artcc : zdc |
| Operator | common carrier : air carrier |
| Make Model Name | Large Transport, Low Wing, 3 Turbojet Eng |
| Flight Phase | cruise other cruise other |
| Route In Use | arrival other |
| Flight Plan | IFR |
| Aircraft 2 | |
| Operator | common carrier : air carrier |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Flight Phase | cruise other cruise other |
| Route In Use | arrival other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : commercial pilot : cfi pilot : atp pilot : instrument |
| Experience | flight time last 90 days : 180 flight time total : 11000 flight time type : 4300 |
| ASRS Report | 123910 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp pilot : flight engineer |
| Experience | flight time last 90 days : 180 flight time total : 7500 flight time type : 2700 |
| ASRS Report | 123901 |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation other anomaly other |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued new clearance none taken : unable |
| Consequence | faa : reviewed incident with flight crew |
| Miss Distance | horizontal : 4000 vertical : 0 |
| Supplementary | |
| Primary Problem | Ambiguous |
| Air Traffic Incident | Operational Deviation Pilot Deviation other |
| Situations | |
| ATC Facility | other physical facility procedure or policy : unspecified |
Narrative:
Flight #abc pbi-bwi at 12,000' on vectors to ott VOR (113.7). ZDC gave us a frequency change to bwi approach. There was another company flight (#abcd) also wbound to bwi. We acknowledged the frequency change with our flight number (abcf). On radio contact with bwi approach (119.7), we gave our flight #abcf and ATIS information. Bwi approach cleared us direct ott VOR (113.7) (was on 010 degree by ZDC), after ott VOR, the 071 degree right, vectors to bwi airport. En route to ott VOR, we observed another air carrier Z large transport at approximately 1/2 mi descending thru our altitude (our 11 O'clock-1 O'clock position) at a very steep angle of descent. We (all 3 crew members) remark how close he came. Normally clearance is issued to cross ott VOR at or below 9000' to maintain 17,000'. After crossing ott VOR still at 12,000', we called bwi approach asking for lower. Controller advised we should be with dca approach frequency (118.1). All frequency (center-approach) were very congested, people stepping on one another. After landing at bwi, I asked the first officer and second officer if the frequency change (bwi 119.7) was given to our flight number. Both said that they were sure the frequency change was given to us (including myself). There are a lot of frequencys that do not have the clarity that they should have.
Original NASA ASRS Text
Title: OPERATIONAL ERROR UNDER AMBIGUOUS CIRCUMSTANCES CREATES A POTENTIAL CONFLICT AND LOSS OF SEPARATION BETWEEN TWO ACR ACFT. TRAFFIC AND COM VOLUME CITED AS CONTRIBUTORY.
Narrative: FLT #ABC PBI-BWI AT 12,000' ON VECTORS TO OTT VOR (113.7). ZDC GAVE US A FREQ CHANGE TO BWI APCH. THERE WAS ANOTHER COMPANY FLT (#ABCD) ALSO WBOUND TO BWI. WE ACKNOWLEDGED THE FREQ CHANGE WITH OUR FLT NUMBER (ABCF). ON RADIO CONTACT WITH BWI APCH (119.7), WE GAVE OUR FLT #ABCF AND ATIS INFO. BWI APCH CLRED US DIRECT OTT VOR (113.7) (WAS ON 010 DEG BY ZDC), AFTER OTT VOR, THE 071 DEG R, VECTORS TO BWI ARPT. ENRTE TO OTT VOR, WE OBSERVED ANOTHER ACR Z LGT AT APPROX 1/2 MI DESCENDING THRU OUR ALT (OUR 11 O'CLOCK-1 O'CLOCK POSITION) AT A VERY STEEP ANGLE OF DSCNT. WE (ALL 3 CREW MEMBERS) REMARK HOW CLOSE HE CAME. NORMALLY CLRNC IS ISSUED TO CROSS OTT VOR AT OR BELOW 9000' TO MAINTAIN 17,000'. AFTER XING OTT VOR STILL AT 12,000', WE CALLED BWI APCH ASKING FOR LOWER. CTLR ADVISED WE SHOULD BE WITH DCA APCH FREQ (118.1). ALL FREQ (CENTER-APCH) WERE VERY CONGESTED, PEOPLE STEPPING ON ONE ANOTHER. AFTER LNDG AT BWI, I ASKED THE F/O AND S/O IF THE FREQ CHANGE (BWI 119.7) WAS GIVEN TO OUR FLT NUMBER. BOTH SAID THAT THEY WERE SURE THE FREQ CHANGE WAS GIVEN TO US (INCLUDING MYSELF). THERE ARE A LOT OF FREQS THAT DO NOT HAVE THE CLARITY THAT THEY SHOULD HAVE.
Data retrieved from NASA's ASRS site as of August 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.