Narrative:

We were between julian and amigo as filed on the pdz 2 arrival. On the arrival, at amigo, it states 'expect clearance to cross at 16000 ft.' the approach controller (on frequency 126.77) gave us the clearance a bit late so we had to hustle to get down, but did so without problem. That clearance was given, as I remember: 'XXX, cross amigo at 16000 ft, cleared the pdz 2 arrival.' when I read it back, I read, 'roger, cleared to cross amigo at or above 16000 ft, cleared the pdz 2 arrival.' I immediately realized I read back the wrong clearance and since this is an arrival I was being cleared for, I had better be sure. So I repeated 'was that at 16000 ft for XXX.' he replied, 'yes at and maintain 16000 ft.' this is where the confusion began. I believe my thought was, I'm cleared to 16000 ft which was an 'expect' that is now satisfied by being cleared to it, so therefore, since the next fix is not an 'expect'(it was a hard altitude) the clearance for the arrival is a clearance to descend on it. I don't remember if he said 'cleared to descend via.' I then treated it as the civet arrival is treated. I fly the civet once a week and believe I got into that mode. So 10 NM or so past amigo, the copilot began a 1000 FPM descent to 12000 ft (tejay). He chose to descend slower in light of the high energy descent earlier to meet 16000 ft at amigo. The aircraft was descending at 700 FPM and was at 600 ft below 16000 ft when ATC asked us to verify level at 16000 ft. I paused and asked if we were cleared the arrival. I instantly popped the aircraft to 16000 ft. The controller didn't reply and gave a call to another aircraft. He didn't sound alarmed at this point. Now we are at 16000 ft and the controller pointed out traffic at 2 O'clock position and I immediately responded 'in sight.' (I think I saw it was 2000 ft below on TCASII.) his response, 'roger, you do have a visual on the B737?' I responded, 'yes I have it in sight.' he said, 'ok XXX verify 16000 ft.' I responded 'yes sir, we are level at 16000 ft.' he then said, 'contact socal on XXX.xx frequency.' I don't recall this frequency. Now with adrenaline kicking, we are confused because I thought I was cleared to descend on this arrival. After landing, the copilot and I discussed it in great detail. We were both convinced we were cleared but may not have recognized whether or not the verbiage was clear, ie, cleared to descend via or just cleared the pdz 2 arrival. Having passed the 'expect' portion of the arrival, heading toward hard altitudes on the rest of the fixes, I was thinking like the civet and so was the first officer. Therefore we were aiming to be at tejay at or above 12000 ft. Conclusion: I think the 'descent via' versus cleared the pdz 2 with it having, all but 1, hard altitudes, is confusing. In fact, all its crossing restrs are hard except the initial or beginning fixes on the arrival.

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Original NASA ASRS Text

Title: AN ACR ACFT LEAVES ITS ASSIGNED XING ALT PREMATURELY WHEN THE FLC MISINTERPS THE STAR ARR CLRNC.

Narrative: WE WERE BTWN JULIAN AND AMIGO AS FILED ON THE PDZ 2 ARR. ON THE ARR, AT AMIGO, IT STATES 'EXPECT CLRNC TO CROSS AT 16000 FT.' THE APCH CTLR (ON FREQ 126.77) GAVE US THE CLRNC A BIT LATE SO WE HAD TO HUSTLE TO GET DOWN, BUT DID SO WITHOUT PROB. THAT CLRNC WAS GIVEN, AS I REMEMBER: 'XXX, CROSS AMIGO AT 16000 FT, CLRED THE PDZ 2 ARR.' WHEN I READ IT BACK, I READ, 'ROGER, CLRED TO CROSS AMIGO AT OR ABOVE 16000 FT, CLRED THE PDZ 2 ARR.' I IMMEDIATELY REALIZED I READ BACK THE WRONG CLRNC AND SINCE THIS IS AN ARR I WAS BEING CLRED FOR, I HAD BETTER BE SURE. SO I REPEATED 'WAS THAT AT 16000 FT FOR XXX.' HE REPLIED, 'YES AT AND MAINTAIN 16000 FT.' THIS IS WHERE THE CONFUSION BEGAN. I BELIEVE MY THOUGHT WAS, I'M CLRED TO 16000 FT WHICH WAS AN 'EXPECT' THAT IS NOW SATISFIED BY BEING CLRED TO IT, SO THEREFORE, SINCE THE NEXT FIX IS NOT AN 'EXPECT'(IT WAS A HARD ALT) THE CLRNC FOR THE ARR IS A CLRNC TO DSND ON IT. I DON'T REMEMBER IF HE SAID 'CLRED TO DSND VIA.' I THEN TREATED IT AS THE CIVET ARR IS TREATED. I FLY THE CIVET ONCE A WK AND BELIEVE I GOT INTO THAT MODE. SO 10 NM OR SO PAST AMIGO, THE COPLT BEGAN A 1000 FPM DSCNT TO 12000 FT (TEJAY). HE CHOSE TO DSND SLOWER IN LIGHT OF THE HIGH ENERGY DSCNT EARLIER TO MEET 16000 FT AT AMIGO. THE ACFT WAS DSNDING AT 700 FPM AND WAS AT 600 FT BELOW 16000 FT WHEN ATC ASKED US TO VERIFY LEVEL AT 16000 FT. I PAUSED AND ASKED IF WE WERE CLRED THE ARR. I INSTANTLY POPPED THE ACFT TO 16000 FT. THE CTLR DIDN'T REPLY AND GAVE A CALL TO ANOTHER ACFT. HE DIDN'T SOUND ALARMED AT THIS POINT. NOW WE ARE AT 16000 FT AND THE CTLR POINTED OUT TFC AT 2 O'CLOCK POS AND I IMMEDIATELY RESPONDED 'IN SIGHT.' (I THINK I SAW IT WAS 2000 FT BELOW ON TCASII.) HIS RESPONSE, 'ROGER, YOU DO HAVE A VISUAL ON THE B737?' I RESPONDED, 'YES I HAVE IT IN SIGHT.' HE SAID, 'OK XXX VERIFY 16000 FT.' I RESPONDED 'YES SIR, WE ARE LEVEL AT 16000 FT.' HE THEN SAID, 'CONTACT SOCAL ON XXX.XX FREQ.' I DON'T RECALL THIS FREQ. NOW WITH ADRENALINE KICKING, WE ARE CONFUSED BECAUSE I THOUGHT I WAS CLRED TO DSND ON THIS ARR. AFTER LNDG, THE COPLT AND I DISCUSSED IT IN GREAT DETAIL. WE WERE BOTH CONVINCED WE WERE CLRED BUT MAY NOT HAVE RECOGNIZED WHETHER OR NOT THE VERBIAGE WAS CLR, IE, CLRED TO DSND VIA OR JUST CLRED THE PDZ 2 ARR. HAVING PASSED THE 'EXPECT' PORTION OF THE ARR, HDG TOWARD HARD ALTS ON THE REST OF THE FIXES, I WAS THINKING LIKE THE CIVET AND SO WAS THE FO. THEREFORE WE WERE AIMING TO BE AT TEJAY AT OR ABOVE 12000 FT. CONCLUSION: I THINK THE 'DSCNT VIA' VERSUS CLRED THE PDZ 2 WITH IT HAVING, ALL BUT 1, HARD ALTS, IS CONFUSING. IN FACT, ALL ITS XING RESTRS ARE HARD EXCEPT THE INITIAL OR BEGINNING FIXES ON THE ARR.

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.