Narrative:

Cruising at FL330 we received clearance 'expect 7500 meters over SL NDB, call ready for descent' or 'expect 7500 meters or SL NDB, call descending.' the exact wording is hazey. However, at the time, I firmly believed we were cleared to descend and I started down. At approximately 32300 ft TCASII showed traffic opposite and at FL310. TCASII said 'traffic, traffic' and at the same time we chose to return to FL330 and ATC reconfirmed that we should return and maintain FL330. Shortly thereafter we were cleared down and handed off to the next controller. Separation appeared to be no less than 1000 ft vertically and approximately 4-5 mi horizontally. All 3 crewmembers were experienced on this section of flight and were surprised and confused that somehow we had possibly misunderstood our clearance. ATC was not concerned about the descent but merely advised us to maintain FL330. Controllers in this area can sometimes be hard to understand and clrncs are not always, 'clear and concise,' however a repeat will often clarify things. So, did we misunderstand the clearance or was it a poor or improper clearance? I am distressed with the thought that perhaps I did not follow the clearance or that I did not clarify a possibly unclr clearance. One must be certain of the clearance. A contributing factor was that we were within approximately 30 mi of the NDB and, that to cross it at the expected altitude, we would have had to descend immediately.

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Original NASA ASRS Text

Title: POTENTIAL CONFLICT. CLRNC INTERP PROB. TCASII SAVES THE DAY AGAIN!!

Narrative: CRUISING AT FL330 WE RECEIVED CLRNC 'EXPECT 7500 METERS OVER SL NDB, CALL READY FOR DSCNT' OR 'EXPECT 7500 METERS OR SL NDB, CALL DSNDING.' THE EXACT WORDING IS HAZEY. HOWEVER, AT THE TIME, I FIRMLY BELIEVED WE WERE CLRED TO DSND AND I STARTED DOWN. AT APPROX 32300 FT TCASII SHOWED TFC OPPOSITE AND AT FL310. TCASII SAID 'TFC, TFC' AND AT THE SAME TIME WE CHOSE TO RETURN TO FL330 AND ATC RECONFIRMED THAT WE SHOULD RETURN AND MAINTAIN FL330. SHORTLY THEREAFTER WE WERE CLRED DOWN AND HANDED OFF TO THE NEXT CTLR. SEPARATION APPEARED TO BE NO LESS THAN 1000 FT VERTLY AND APPROX 4-5 MI HORIZLY. ALL 3 CREWMEMBERS WERE EXPERIENCED ON THIS SECTION OF FLT AND WERE SURPRISED AND CONFUSED THAT SOMEHOW WE HAD POSSIBLY MISUNDERSTOOD OUR CLRNC. ATC WAS NOT CONCERNED ABOUT THE DSCNT BUT MERELY ADVISED US TO MAINTAIN FL330. CTLRS IN THIS AREA CAN SOMETIMES BE HARD TO UNDERSTAND AND CLRNCS ARE NOT ALWAYS, 'CLR AND CONCISE,' HOWEVER A REPEAT WILL OFTEN CLARIFY THINGS. SO, DID WE MISUNDERSTAND THE CLRNC OR WAS IT A POOR OR IMPROPER CLRNC? I AM DISTRESSED WITH THE THOUGHT THAT PERHAPS I DID NOT FOLLOW THE CLRNC OR THAT I DID NOT CLARIFY A POSSIBLY UNCLR CLRNC. ONE MUST BE CERTAIN OF THE CLRNC. A CONTRIBUTING FACTOR WAS THAT WE WERE WITHIN APPROX 30 MI OF THE NDB AND, THAT TO CROSS IT AT THE EXPECTED ALT, WE WOULD HAVE HAD TO DSND IMMEDIATELY.

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.