PLT OF A SINGLE PLT CPR JET MADE A MISSED APCH DUE TO SETTING ERROR OF THE GPS NAVIGATIONAL EQUIP.

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ON VOR APCH TO SMO; WE WERE BROUGHT IN HIGH BY ATC. BROKE OUT AND WERE TOO HIGH TO LAND. THEY GAVE A VECTOR AND CLB FOR A MISSED APCH! WE WERE VECTORED TO INTERCEPT THE APCH VOR RADIAL AND BEGAN A NORMAL APCH. I WAS USING A RECENTLY INSTALLED GPS TO IDENT BEVEY INTXN FOR A LET- DOWN ALT. BOTH GPS'S SHOWED US 5 MI INBOUND FROM BEVEY CONTRADICTING THE DME READING ON THE VOR WHICH SHOWED US NOT YET TO BEVEY. BEVEY INTXN WAS IN BOTH GPS UNITS ON THE FIRST APCH. DURING THE MISSED APCH ON INITIAL CLB IN PREPARATION FOR A NEW APCH; I PUSHED THE DIRECT TO BUTTON ON BOTH GPS TO IDENT OUR LOCATION FROM BEVEY! I THEN TOOK VECTORS AND ALT ASSIGNMENTS AND WAS VECTORED ONTO THE VOR RADIAL. AFTER INTERCEPT; I TRIED TO DETERMINE MY EXACT POS ON THE RADIAL BY REF TO BOTH THE VOR DME READING AND THE 2 GPS UNITS. THE CURSOR ON BOTH GPS UNITS SHOWED US 5 MI PAST BEVEY AND THE DME SHOWED ABOUT 5 MI TO BEVEY. I FAILED; (DUE TO INADEQUATE TRAINING WITH GPS); TO REALIZE THAT THE DIRECT TO BUTTON WAS PUSHED PRIOR TO PASSING BEVEY WHILE OUTBOUND AND WAS THUS GIVING A REVERSE READING. ATC RADIOED WITH AN ALT ALTERATION AND I BEGAN AN IMMEDIATE CLB. WHILE CLBING; I WAS TRANSFERRED TO TWR AND THEY GAVE ANOTHER ALT ALTERATION AND A COURSE CORRECTION AS I HAD GONE OFF THE RADIAL ON THE CLB. I DISCONNECTED THE AUTOPLT FOR THE CLB; AND NOW SEE THAT AS AN ERROR; AS IT WOULD HAVE KEPT ME ON THE RADIAL. WE BROKE OUT SECONDS AFTER THE TWR'S ALT ALTERATION AND LANDED. A MAJOR CONTRIBUTING FACTOR TO THE ERROR WAS ALLOWING A SINGLE ENG LOW TIME NON-INST PLT TO RIDE IN THE R SEAT! HE WAS EXTREMELY DISTRACTING; ASKING QUESTIONS; GIVING ADVICE; TRYING TO CHANGE RADIOS AND SET THE ALT PRE-SELECT! I BELIEVE WITHOUT THIS DISTR I WOULD HAVE BEEN FURTHER AHEAD OF THE AIRPLANE AND FOUND THE GPS ERROR BEFORE DSNDING TOO SOON! ON THE NEXT LEG OF THE FLT FROM SMO TO LOGAN; UT; HE SAT IN THE BACK AND A VERY BUSY FLT OUT OF THE LOS ANGLES BASIN WAS AN UNEVENTFUL PLEASURE.