Narrative:

While flying toward tresa intersection, ATC gave us a clearance to cross 10 DME north of cmk at 8000 ft. Usually, when we get this crossing restr referenced to cmk, we are also cleared direct to cmk. We began our descent, and turned toward cmk on a direct course. After some discussion with my first officer (PF), we determined that we never received the usual accompanying clearance direct to cmk. We then turned back toward V433 in order to intercept the cmk 356 degree radial as close to tresa as possible. That had been our previous clearance. That's when our problems began. ATC was forced to vector another aircraft in order to avoid losing separation with us. At that point, the controller queried us as to why we had turned back toward the left. We explained that we had never received nor acknowledged a clearance for direct cmk. I said that under the circumstances, we decided to return to our original course until we could question the controller and determine his intentions. He was clearly annoyed that we turned left back toward tresa, so I must conclude that he had intended for us to proceed direct to cmk. He just simply forgot to issue the verbal clearance to us. He was very busy at the time, and this fact contributed both to his oversight and to our difficulty in trying to contact him for clarification. It was a case of knowing what to do, but not having the opportunity to do it prior to upsetting the natural flow of things. We felt at the time (and still do) that we should not try to interpret ATC's intentions, but rather, we should comply with our previous clearance until we could confirm the intentions of ATC. We may have confused ATC by first turning toward cmk and then turning back to the left. Because of this, he may have believed that he had already cleared us direct. The frequency congestion contributed to the confusion on both sides because we had no opportunity to confirm anything with ATC prior to closing on the other aircraft. I also think that we should not be so quick to assume that an issued clearance is the standard one that we have always done before.

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Original NASA ASRS Text

Title: FLC FLEW ANTICIPATED ROUTING AND WHEN UNABLE TO CONTACT ATC TO VERIFY, THEY RETURNED TO THE ORIGINAL CLRNC. APCH CTLR INTERVENED. DEV FROM CLRNC RTE.

Narrative: WHILE FLYING TOWARD TRESA INTXN, ATC GAVE US A CLRNC TO CROSS 10 DME N OF CMK AT 8000 FT. USUALLY, WHEN WE GET THIS XING RESTR REFERENCED TO CMK, WE ARE ALSO CLRED DIRECT TO CMK. WE BEGAN OUR DSCNT, AND TURNED TOWARD CMK ON A DIRECT COURSE. AFTER SOME DISCUSSION WITH MY FO (PF), WE DETERMINED THAT WE NEVER RECEIVED THE USUAL ACCOMPANYING CLRNC DIRECT TO CMK. WE THEN TURNED BACK TOWARD V433 IN ORDER TO INTERCEPT THE CMK 356 DEG RADIAL AS CLOSE TO TRESA AS POSSIBLE. THAT HAD BEEN OUR PREVIOUS CLRNC. THAT'S WHEN OUR PROBS BEGAN. ATC WAS FORCED TO VECTOR ANOTHER ACFT IN ORDER TO AVOID LOSING SEPARATION WITH US. AT THAT POINT, THE CTLR QUERIED US AS TO WHY WE HAD TURNED BACK TOWARD THE L. WE EXPLAINED THAT WE HAD NEVER RECEIVED NOR ACKNOWLEDGED A CLRNC FOR DIRECT CMK. I SAID THAT UNDER THE CIRCUMSTANCES, WE DECIDED TO RETURN TO OUR ORIGINAL COURSE UNTIL WE COULD QUESTION THE CTLR AND DETERMINE HIS INTENTIONS. HE WAS CLRLY ANNOYED THAT WE TURNED L BACK TOWARD TRESA, SO I MUST CONCLUDE THAT HE HAD INTENDED FOR US TO PROCEED DIRECT TO CMK. HE JUST SIMPLY FORGOT TO ISSUE THE VERBAL CLRNC TO US. HE WAS VERY BUSY AT THE TIME, AND THIS FACT CONTRIBUTED BOTH TO HIS OVERSIGHT AND TO OUR DIFFICULTY IN TRYING TO CONTACT HIM FOR CLARIFICATION. IT WAS A CASE OF KNOWING WHAT TO DO, BUT NOT HAVING THE OPPORTUNITY TO DO IT PRIOR TO UPSETTING THE NATURAL FLOW OF THINGS. WE FELT AT THE TIME (AND STILL DO) THAT WE SHOULD NOT TRY TO INTERPRET ATC'S INTENTIONS, BUT RATHER, WE SHOULD COMPLY WITH OUR PREVIOUS CLRNC UNTIL WE COULD CONFIRM THE INTENTIONS OF ATC. WE MAY HAVE CONFUSED ATC BY FIRST TURNING TOWARD CMK AND THEN TURNING BACK TO THE L. BECAUSE OF THIS, HE MAY HAVE BELIEVED THAT HE HAD ALREADY CLRED US DIRECT. THE FREQ CONGESTION CONTRIBUTED TO THE CONFUSION ON BOTH SIDES BECAUSE WE HAD NO OPPORTUNITY TO CONFIRM ANYTHING WITH ATC PRIOR TO CLOSING ON THE OTHER ACFT. I ALSO THINK THAT WE SHOULD NOT BE SO QUICK TO ASSUME THAT AN ISSUED CLRNC IS THE STANDARD ONE THAT WE HAVE ALWAYS DONE BEFORE.

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.