Narrative:

At approximately XA00 I was flying as captain to las. This was a day trip for me, not my regular job or aircraft that I fly (also a westwind) on a routine basis. About 100 mi from las, I heard radio traffic stating to expect holding into las due to vip movement. We were reclred from peach springs 1 to the tyssn 1 RNAV arrival, and told to descend and maintain 13000 ft. Subsequent to that clearance, we were given clearance to 'hold at kaddy as published' and given an efc time. I asked for and received permission for 10 mi legs in the hold. During our second turn in the holding pattern, and approximately 10 mi from kaddy intersection, we were cleared direct to kaddy to resume the arrival and instructed to comply with the altitudes depicted on the arrival. At that time, we began having problems with the trimble GPS (the westwind that I normally fly has a gnsxls). The trimble unit was slow in its calculations and did not recognize some of the waypoints on the arrival. At the same time, I heard what I believed the controller to say, 'descend and maintain 10000 ft,' and this was read back to him. 10000 ft was set in the altitude select. 10000 ft is also the next mandatory altitude for crossing the next waypoint on the arrival, and it would make sense that perhaps he wanted us there now. In my mind, this negated the clearance to comply with the depicted arrival altitudes, which included crossing kaddy at 12000 ft. We continued our descent towards 10000 ft and just prior to reaching kaddy and at an altitude of 11000 ft, the controller came on and told us that our clearance was to comply with the altitudes depicted on the arrival, and why weren't we at 11000 ft? I replied that I had understood the clearance to be descend and maintain 10000 ft. He told us to maintain 11000 ft. He then informed us that we had missed kaddy by 3 mi, so I keyed the microphone and apologized for the confusion and that we seemed to be having some problems with the GPS accepting data. At that point, he gave us a heading of 360 degrees to rejoin the arrival. From that point, the remainder of the arrival and approach were normal. There did not seem to be any conflicts that arose out of this situation, and he seemed satisfied with my explanation. Extenuating circumstances included a relatively new copilot who was a bit overwhelmed by the speed at which changes were occurring, and as a result, me having to do the flying, navigating, and communicating. After we landed, my copilot, who is employed by the company that I was day plting for, informed me that the trimble GPS did not have some of the waypoints on the RNAV arrival in its database. Obviously, the missed altitude was an error on my part, and is the first occurrence of its kind in the 15 yrs I have been flying a cpr jet. I should have verified altitudes with the approach controller, even though I thought I was clear in our descent instructions. In retrospect, I should have informed the approach controller of the problem with the GPS accepting RNAV waypoints and asked for a radar vector. This distraction, along with the others mentioned, was a main contributing factor in overlooking the mandatory crossing of kaddy at 12000 ft, and continuing the descent towards 10000 ft, which is what I believe I heard and read back, even though we had reviewed the arrival and discussed these altitudes. Upon returning to my home base, I discussed the events with my chief pilot and he urged me to report this event to you. I pride myself on demonstrating the utmost in professionalism, and am amazed how quickly a routine flight became a bit chaotic. As they say, it's never any one thing that gets you in trouble, but rather a chain of events, and this was certainly the case on this day.

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Original NASA ASRS Text

Title: WW24 PIC DSNDS FROM LAS TYSSN STAR, DISTR BY GPS EQUIP PROBS, HOLDING INSTRUCTION, OVERWHELMED FO AND ASSUMED INTENT OF L30 STAR CLRNC.

Narrative: AT APPROX XA00 I WAS FLYING AS CAPT TO LAS. THIS WAS A DAY TRIP FOR ME, NOT MY REGULAR JOB OR ACFT THAT I FLY (ALSO A WESTWIND) ON A ROUTINE BASIS. ABOUT 100 MI FROM LAS, I HEARD RADIO TFC STATING TO EXPECT HOLDING INTO LAS DUE TO VIP MOVEMENT. WE WERE RECLRED FROM PEACH SPRINGS 1 TO THE TYSSN 1 RNAV ARR, AND TOLD TO DSND AND MAINTAIN 13000 FT. SUBSEQUENT TO THAT CLRNC, WE WERE GIVEN CLRNC TO 'HOLD AT KADDY AS PUBLISHED' AND GIVEN AN EFC TIME. I ASKED FOR AND RECEIVED PERMISSION FOR 10 MI LEGS IN THE HOLD. DURING OUR SECOND TURN IN THE HOLDING PATTERN, AND APPROX 10 MI FROM KADDY INTXN, WE WERE CLRED DIRECT TO KADDY TO RESUME THE ARR AND INSTRUCTED TO COMPLY WITH THE ALTS DEPICTED ON THE ARR. AT THAT TIME, WE BEGAN HAVING PROBS WITH THE TRIMBLE GPS (THE WESTWIND THAT I NORMALLY FLY HAS A GNSXLS). THE TRIMBLE UNIT WAS SLOW IN ITS CALCULATIONS AND DID NOT RECOGNIZE SOME OF THE WAYPOINTS ON THE ARR. AT THE SAME TIME, I HEARD WHAT I BELIEVED THE CTLR TO SAY, 'DSND AND MAINTAIN 10000 FT,' AND THIS WAS READ BACK TO HIM. 10000 FT WAS SET IN THE ALT SELECT. 10000 FT IS ALSO THE NEXT MANDATORY ALT FOR XING THE NEXT WAYPOINT ON THE ARR, AND IT WOULD MAKE SENSE THAT PERHAPS HE WANTED US THERE NOW. IN MY MIND, THIS NEGATED THE CLRNC TO COMPLY WITH THE DEPICTED ARR ALTS, WHICH INCLUDED XING KADDY AT 12000 FT. WE CONTINUED OUR DSCNT TOWARDS 10000 FT AND JUST PRIOR TO REACHING KADDY AND AT AN ALT OF 11000 FT, THE CTLR CAME ON AND TOLD US THAT OUR CLRNC WAS TO COMPLY WITH THE ALTS DEPICTED ON THE ARR, AND WHY WEREN'T WE AT 11000 FT? I REPLIED THAT I HAD UNDERSTOOD THE CLRNC TO BE DSND AND MAINTAIN 10000 FT. HE TOLD US TO MAINTAIN 11000 FT. HE THEN INFORMED US THAT WE HAD MISSED KADDY BY 3 MI, SO I KEYED THE MIKE AND APOLOGIZED FOR THE CONFUSION AND THAT WE SEEMED TO BE HAVING SOME PROBS WITH THE GPS ACCEPTING DATA. AT THAT POINT, HE GAVE US A HDG OF 360 DEGS TO REJOIN THE ARR. FROM THAT POINT, THE REMAINDER OF THE ARR AND APCH WERE NORMAL. THERE DID NOT SEEM TO BE ANY CONFLICTS THAT AROSE OUT OF THIS SIT, AND HE SEEMED SATISFIED WITH MY EXPLANATION. EXTENUATING CIRCUMSTANCES INCLUDED A RELATIVELY NEW COPLT WHO WAS A BIT OVERWHELMED BY THE SPD AT WHICH CHANGES WERE OCCURRING, AND AS A RESULT, ME HAVING TO DO THE FLYING, NAVING, AND COMMUNICATING. AFTER WE LANDED, MY COPLT, WHO IS EMPLOYED BY THE COMPANY THAT I WAS DAY PLTING FOR, INFORMED ME THAT THE TRIMBLE GPS DID NOT HAVE SOME OF THE WAYPOINTS ON THE RNAV ARR IN ITS DATABASE. OBVIOUSLY, THE MISSED ALT WAS AN ERROR ON MY PART, AND IS THE FIRST OCCURRENCE OF ITS KIND IN THE 15 YRS I HAVE BEEN FLYING A CPR JET. I SHOULD HAVE VERIFIED ALTS WITH THE APCH CTLR, EVEN THOUGH I THOUGHT I WAS CLR IN OUR DSCNT INSTRUCTIONS. IN RETROSPECT, I SHOULD HAVE INFORMED THE APCH CTLR OF THE PROB WITH THE GPS ACCEPTING RNAV WAYPOINTS AND ASKED FOR A RADAR VECTOR. THIS DISTR, ALONG WITH THE OTHERS MENTIONED, WAS A MAIN CONTRIBUTING FACTOR IN OVERLOOKING THE MANDATORY XING OF KADDY AT 12000 FT, AND CONTINUING THE DSCNT TOWARDS 10000 FT, WHICH IS WHAT I BELIEVE I HEARD AND READ BACK, EVEN THOUGH WE HAD REVIEWED THE ARR AND DISCUSSED THESE ALTS. UPON RETURNING TO MY HOME BASE, I DISCUSSED THE EVENTS WITH MY CHIEF PLT AND HE URGED ME TO RPT THIS EVENT TO YOU. I PRIDE MYSELF ON DEMONSTRATING THE UTMOST IN PROFESSIONALISM, AND AM AMAZED HOW QUICKLY A ROUTINE FLT BECAME A BIT CHAOTIC. AS THEY SAY, IT'S NEVER ANY ONE THING THAT GETS YOU IN TROUBLE, BUT RATHER A CHAIN OF EVENTS, AND THIS WAS CERTAINLY THE CASE ON THIS DAY.

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.