A B747-400 FLC BECOMES CONFUSED OVER THE DESIGNATORS OF ZAK AND ZOA AND WHAT EACH REPRESENTS.

1999-02 · NASA ASRS report 429792

Date: 1999-02 · Aircraft: B747-400

Anomalies: other-unspecified

Synopsis

A B747-400 FLC BECOMES CONFUSED OVER THE DESIGNATORS OF ZAK AND ZOA AND WHAT EACH REPRESENTS.

Narrative

ATTACHED IS A DESCRIPTION OF THE EVENT/SIT AS RECORDED INFLT JUST AFTER IT OCCURRED. FOR CLARIFICATION; 'HOWGOZIT' OF OUR FLT (ITEM #1) IS INCLUDED. A NOTAM IS ITEM #2; AND COMS ARE ITEMS #3 THROUGH #5. THE COMS DIFFICULTIES THAT OUR FLT ENCOUNTERED WERE NOT SO UNUSUAL FOR THIS LOCATION; AND RECEPTION PROBS WERE RESOLVED AS THE FLT PROGRESSED EBOUND. HOWEVER; I BELIEVE THAT THE NOTAM WHICH TRIES TO PROVIDE GUIDANCE TO FLCS FOR COM PROCS IS CONFUSING. IT REFERS TO ACFT EXITING ZOA FIR. WHAT'S THAT? WE WERE LOGGED ONTO ZAK AND; ACCORDING TO EVERY CHART WE COULD FIND; TALKING TO OAKLAND. WE WERE LOGGED ON TO ZAK USING CPDLC. WE WERE NOT LOGGED ON TO ZOA; AND NO MEMBER OF THE CREW WAS AWARE OF SUCH AN IDENT FOR OAKLAND. WHILE NAVING IN CLASS 2 AIRSPACE ACR X WAS COMMUNICATING VIA CPDLC AND WAS LOGGED ON TO ZAK FOR ZOA. ESTIMATE FOR PRETTY WAS YY16Z. FIR ESTIMATE WAS YY32Z. AT +YY29 A MESSAGE WAS RECEIVED FROM 'ATC UPLINK' TO CONTACT CZVR CTR ON 133.4 MHZ. A RESPONSE WAS SENT AT YY30Z. SEVERAL CALLS WERE MADE ON 133.4 TO ESTABLISH CONTACT AND GIVE PROGRESS WITH NO RESPONSE. A POS RPT WAS MADE IN THE BLIND. ABOUT THIS TIME CPDLC MESSAGE (ATC MESSAGE) APPEARED SOMETHING LIKE 'ATC COM LOG-OFF' FROM OAKLAND (ZAK). DURING THIS TIME AN HF SELCAL FROM SFO COMMERCIAL RADIO CAME IN; AND WE WERE UNABLE TO ESTABLISH VOICE CONTACT DUE TO POOR HF COMS QUALITY. AFTER SWITCHING TO THE SECONDARY FREQ WE RECEIVED A VOICE CALL (WEAK AND BARELY READABLE) TO CONTACT VANCOUVER ON 135.2. WE DID SO AND UPON CALL-UP THE CTR SAID 'RADAR CONTACT; NO POS RPTS REQUIRED.' ABOUT THIS TIME; OR JUST AFTER; AN ACARS MESSAGE WAS RECEIVED AT YY38Z 'ZOA REQUESTS ACR X CONTACT CZVR CTR 135.2.' BUT IN THE MEANTIME VANCOUVER HAD SWITCHED US TO ANOTHER FREQ. WE THEN CALLED VANCOUVER CTR TO INQUIRE AS TO THE NEED FOR A CHANGE TO 135.2 AND THEY TOLD US TO DISREGARD. AT YY47Z ANOTHER ACARS MESSAGE WAS RECEIVED (AND ACCEPTED) INDICATING THAT PER NOTAM; WE WERE REQUIRED TO CONTACT COMMERCIAL RADIO PRIOR TO EXITING AT ZOA FIR. THE NOTAM INDICATES DATALINK USERS ARE TO CONTACT COMMERCIAL RADIO FOR VHF/HF FREQ IN NEXT SECTOR PRIOR TO EXITING ZOA FIR AND GIVES SEVERAL FREQS; INCLUDING 135.2. ACR PLOTTING CHART INDICATES FIR AS 'OAKLAND OCEANIC ZAK FIR AS DOES COMMERCIAL CHART PACIFIC OCEAN AND CANADA-ALASKA HIGH ALT ENRTE CHART. WE CALLED ZSE TO CONFIRM THE NOMENCLATURE OF OAKLAND FIR. THEY INDICATED IT IS ZOA AND ANCHORAGE IS ZAK. CONFLICTING; OR AT LEAST APPARENTLY CONFUSING; VERBIAGE ALONG WITH AN ASSIGNMENT OF A FREQ BY THE CPDLC AND PAST EXPERIENCE OF POOR VHF COM APCHING VANCOUVER ALLOWED THE CREW TO BELIEVE THEY WERE COMMUNICATING AS ATC HAD DIRECTED. THIS IS EXACERBATED BY THE RELATIVELY NEW USE OF CPDLC ON AN EASTERLY ROUTING IN THIS AREA AND THE LACK OF RESPONSES TO POS RPTS FROM ATC WHEN USING THIS METHOD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR PARTICIPATED IN FANS STRUCTURED CALLBACK PROGRAM. RPTR HAD NEVER HEARD OF ZOA OR EVEN KNEW WHERE THE ZOA ADIZ WAS LOCATED. HE ONLY KNEW ZOA DESIGNATION AS ZAK. WHEN THE ZSE CTLR SAID ZAK WAS ANCHORAGE CTR; THEN THE FLC WAS CONFUSED. THEY WERE ABLE TO MAKE RADIO CONTACT; BUT NOT WHEN THEY EXPECTED TO. THIS IS WHAT CAUSED THEM TO ASK QUESTIONS OF THE CTLRS. IT WAS NEVER CLR UNTIL ANALYST EXPLAINED THE DESIGNATORS IN EASY TO UNDERSTAND TERMS.

Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.

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