Narrative:

Westbound on A342 prior to grind intersection, we requested climb to FL310. A long time passed and our fuel had burned down sufficiently to climb higher so the captain told me to request FL330. We were again told by sfo arinc to standby. The designated captain traded seats with the international officer. Approaching grind the information officer and I were verifying the next waypoint (latitude/longitude) the desired track and distance on 3 navigation sets. I appeared to log the wing, fuel and airep forms. Just as we reached grind ATC cleared us to climb and maintain FL310 or FL330. It was my understanding that we were cleared to FL330 and as such I placed 330 in the altitude alert window, and read back FL330. We then passed grind intersection at FL290 and began our climb. Several mins later after several unsuccessful SELCAL checks and attempts to establish clear HF communication. ATC requested to know what our grind intersection altitude had been. I replied that it was FL290, but that we had climbed immediately after crossing the fix and were now level at FL330. ATC asked for verification that we were now at FL330. About 5 mins later hnl communication radio called and cleared us to maintain FL310. The I/O instructed me to make a request for FL350, which I did, and ATC repeated their clearance to maintain FL310. We descended to FL310, reported our new altitude and ATC informed us that our assigned altitude had been FL310 all along and not ever FL330. We called ZOA and talked with quality assurance supervisor. It was his brief that ATC had cleared us only to FL310, and that my readback indicated that I had understood the clearance and stated FL310. Each person in the cockpit was alert (2 pilots and an F/east) and all were monitoring the HF radios at the time the clearance was received and read back. We are unanimous in our belief that FL330 was assigned. The only plausible explanation for the mistaken altitude selection and flight path deviation that I can think of is that clearance was issued at a time of relatively high cockpit activity; i.e., waypoint verification, aireps, logs, fuel checks, etc, combined wit a crew expectation of receiving a clearance to FL330. It took about 15 mins to finally clear up the understanding of what our altitude was versus the clearance. It is possible that commercial communication visibility-a-visibility oakland oceanic played some part.

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Original NASA ASRS Text

Title: ACR WDB ALT DEVIATION OVERSHOT CLRNC ALT DURING EXTENDED OVERWATER OPERATION USING COMMERCIAL RADIO FOR CLRNC RELAY.

Narrative: WBND ON A342 PRIOR TO GRIND INTXN, WE REQUESTED CLB TO FL310. A LONG TIME PASSED AND OUR FUEL HAD BURNED DOWN SUFFICIENTLY TO CLB HIGHER SO THE CAPT TOLD ME TO REQUEST FL330. WE WERE AGAIN TOLD BY SFO ARINC TO STANDBY. THE DESIGNATED CAPT TRADED SEATS WITH THE INTL OFFICER. APCHING GRIND THE INFO OFFICER AND I WERE VERIFYING THE NEXT WAYPOINT (LAT/LONGITUDE) THE DESIRED TRACK AND DISTANCE ON 3 NAV SETS. I APPEARED TO LOG THE WING, FUEL AND AIREP FORMS. JUST AS WE REACHED GRIND ATC CLRED US TO CLB AND MAINTAIN FL310 OR FL330. IT WAS MY UNDERSTANDING THAT WE WERE CLRED TO FL330 AND AS SUCH I PLACED 330 IN THE ALT ALERT WINDOW, AND READ BACK FL330. WE THEN PASSED GRIND INTXN AT FL290 AND BEGAN OUR CLB. SEVERAL MINS LATER AFTER SEVERAL UNSUCCESSFUL SELCAL CHKS AND ATTEMPTS TO ESTABLISH CLR HF COM. ATC REQUESTED TO KNOW WHAT OUR GRIND INTXN ALT HAD BEEN. I REPLIED THAT IT WAS FL290, BUT THAT WE HAD CLBED IMMEDIATELY AFTER XING THE FIX AND WERE NOW LEVEL AT FL330. ATC ASKED FOR VERIFICATION THAT WE WERE NOW AT FL330. ABOUT 5 MINS LATER HNL COM RADIO CALLED AND CLRED US TO MAINTAIN FL310. THE I/O INSTRUCTED ME TO MAKE A REQUEST FOR FL350, WHICH I DID, AND ATC REPEATED THEIR CLRNC TO MAINTAIN FL310. WE DSNDED TO FL310, RPTED OUR NEW ALT AND ATC INFORMED US THAT OUR ASSIGNED ALT HAD BEEN FL310 ALL ALONG AND NOT EVER FL330. WE CALLED ZOA AND TALKED WITH QUALITY ASSURANCE SUPVR. IT WAS HIS BRIEF THAT ATC HAD CLRED US ONLY TO FL310, AND THAT MY READBACK INDICATED THAT I HAD UNDERSTOOD THE CLRNC AND STATED FL310. EACH PERSON IN THE COCKPIT WAS ALERT (2 PLTS AND AN F/E) AND ALL WERE MONITORING THE HF RADIOS AT THE TIME THE CLRNC WAS RECEIVED AND READ BACK. WE ARE UNANIMOUS IN OUR BELIEF THAT FL330 WAS ASSIGNED. THE ONLY PLAUSIBLE EXPLANATION FOR THE MISTAKEN ALT SELECTION AND FLT PATH DEVIATION THAT I CAN THINK OF IS THAT CLRNC WAS ISSUED AT A TIME OF RELATIVELY HIGH COCKPIT ACTIVITY; I.E., WAYPOINT VERIFICATION, AIREPS, LOGS, FUEL CHKS, ETC, COMBINED WIT A CREW EXPECTATION OF RECEIVING A CLRNC TO FL330. IT TOOK ABOUT 15 MINS TO FINALLY CLR UP THE UNDERSTANDING OF WHAT OUR ALT WAS VERSUS THE CLRNC. IT IS POSSIBLE THAT COMMERCIAL COM VIS-A-VIS OAKLAND OCEANIC PLAYED SOME PART.

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.