Narrative:

Initially at FL290, instructed to cross 'misen' at FL240 by ZLA. This was my second time to fly or see an RNAV arrival. First officer was flying. As we approached dag for the skebr RNAV one arrival into las we were xchking the legs page for navigation and ensuring both navigation switches were in the navigation position. The descent page said we were well before the descent point, however, this was based on crossing misen at or above FL240, not FL240. By the time I realized we needed to cross misen at FL240 it was impossible to make the altitude. I directed the first officer to begin a descent and told ZLA we would not make the restr. He reclred us to 'descend to FL240' and there was no apparent traffic conflict. Remainder of flight uneventful. Permit me to editorialize. I feel the reason for this problem was neither I or my first officer are properly trained to fly RNAV arrs. Prior to the RNAV arrival the night before the event, my first officer and I restudied the bulletin about RNAV arrs and reviewed the STAR into las. I asked if he knew what 'mim' meant, if it were written by the altitude on the STAR. He did not know. I surmised or guessed it was an altitude restr 'at or above' or 'at or below' as you can have either on a departure or arrival? Is it what the FMS defaults to when the arrival is entered? I still don't know. Supplemental information from acn 536974: I was at fl 260 when I crossed misen. On the legs page it showed misen 24000 ft 'a,' so I was waiting for the descent profile/slope bars to lead me down to cross misen at FL240. Obviously that never happened due to the 'a.' this was my first time to fly an RNAV arrival profile. I also don't know what 'mim' on the arrs means and can't seen to find the definition. Ok, I found 'mim,' it means 'minimum,' at or above? However, it is not on the STAR's section of the intro to the commercial chart.

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Original NASA ASRS Text

Title: XING RESTR MISSED AT MISEN ON THE SKEBR RNAV ONE ARR TO LAS VEGAS, NV. THE FLC WAS UNAWARE AS TO WHAT SOME CHART NOTATIONS MEANT.

Narrative: INITIALLY AT FL290, INSTRUCTED TO CROSS 'MISEN' AT FL240 BY ZLA. THIS WAS MY SECOND TIME TO FLY OR SEE AN RNAV ARR. FO WAS FLYING. AS WE APCHED DAG FOR THE SKEBR RNAV ONE ARR INTO LAS WE WERE XCHKING THE LEGS PAGE FOR NAV AND ENSURING BOTH NAV SWITCHES WERE IN THE NAV POS. THE DSCNT PAGE SAID WE WERE WELL BEFORE THE DSCNT POINT, HOWEVER, THIS WAS BASED ON XING MISEN AT OR ABOVE FL240, NOT FL240. BY THE TIME I REALIZED WE NEEDED TO CROSS MISEN AT FL240 IT WAS IMPOSSIBLE TO MAKE THE ALT. I DIRECTED THE FO TO BEGIN A DSCNT AND TOLD ZLA WE WOULD NOT MAKE THE RESTR. HE RECLRED US TO 'DSND TO FL240' AND THERE WAS NO APPARENT TFC CONFLICT. REMAINDER OF FLT UNEVENTFUL. PERMIT ME TO EDITORIALIZE. I FEEL THE REASON FOR THIS PROB WAS NEITHER I OR MY FO ARE PROPERLY TRAINED TO FLY RNAV ARRS. PRIOR TO THE RNAV ARR THE NIGHT BEFORE THE EVENT, MY FO AND I RESTUDIED THE BULLETIN ABOUT RNAV ARRS AND REVIEWED THE STAR INTO LAS. I ASKED IF HE KNEW WHAT 'MIM' MEANT, IF IT WERE WRITTEN BY THE ALT ON THE STAR. HE DID NOT KNOW. I SURMISED OR GUESSED IT WAS AN ALT RESTR 'AT OR ABOVE' OR 'AT OR BELOW' AS YOU CAN HAVE EITHER ON A DEP OR ARR? IS IT WHAT THE FMS DEFAULTS TO WHEN THE ARR IS ENTERED? I STILL DON'T KNOW. SUPPLEMENTAL INFO FROM ACN 536974: I WAS AT FL 260 WHEN I CROSSED MISEN. ON THE LEGS PAGE IT SHOWED MISEN 24000 FT 'A,' SO I WAS WAITING FOR THE DSCNT PROFILE/SLOPE BARS TO LEAD ME DOWN TO CROSS MISEN AT FL240. OBVIOUSLY THAT NEVER HAPPENED DUE TO THE 'A.' THIS WAS MY FIRST TIME TO FLY AN RNAV ARR PROFILE. I ALSO DON'T KNOW WHAT 'MIM' ON THE ARRS MEANS AND CAN'T SEEN TO FIND THE DEFINITION. OK, I FOUND 'MIM,' IT MEANS 'MINIMUM,' AT OR ABOVE? HOWEVER, IT IS NOT ON THE STAR'S SECTION OF THE INTRO TO THE COMMERCIAL CHART.

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.