BE 36 PLT DEVIATED FROM RNAV APCH AFTER 'ACTIVATING' THE APCH IN THE GPS.

Narrative

I WAS FLYING FROM BED-HYA AND WAS ON AN INST FLT PLAN. ENRTE THE CTLR ASKED ME WHAT APCH I WANTED AND A REQUESTED THE HYA RNAV (GPS) RWY 6. THE CTLR GAVE ME DIRECT JEBIM (THE IAF); WHICH I ENTERED INTO MY GPS FLT PLAN. I ALSO SELECTED THE GPS RWY 6 APCH AND LOADED IT WITH 'VECTORS' TRANSITION SELECTED. I DECREASED PWR SETTINGS TO ACHIEVE 90 KIAS FOR APCH. THE WAYPOINTS WERE DISPLAYED ON THE MAP. WHEN I WAS 1.6 NM FROM JEBIM; I ACTIVATED THE APCH AND IMMEDIATELY LOST THE JEBIM AND FIXUG WAYPOINTS FROM THE MOVING MAP. I RELOADED THE APCH; FOUND THE MAGENTA LINE ON THE DISPLAY AND PROCEEDED TO INTERCEPT THE COURSE SE OF THE FAF (COVOD). I REMEMBERED THE PLTS AXIOM 'AVIATE; NAV; COMMUNICATE' AS I WAS PERFORMING THESE OPS. AT THIS POINT I GOT A CALL FROM THE CTLR; ASKING ME WHY I HAD DEVIATED FROM THE APCH; AND I TOLD HIM THAT I HAD LOST WAYPOINTS AND HAD TO REPROGRAM. WHEN HE ASKED ME WHY I HADN'T COMMUNICATED THIS TO HIM I SAID SOMETHING TO THE EFFECT THAT I WAS VERY BUSY DURING THE PAST FEW SECONDS WITH LOSS OF WAYPOINTS. I INTERCEPTED THE COURSE AT 2000 FT AGL AND PROCEEDED TO A NORMAL LNDG ON RWY 6. AFTER I HAD TRANSPORTED THE PATIENT AND RETURNED TO MY HOME; I OPENED UP THE MANUFACTURER'S TRAINING SIMULATOR ON MY COMPUTER AND 'FLEW' THE APCH ON THE COMPUTER. I FOUND THAT MY WAYPOINTS WERE DROPPED WHEN THE APCH WAS ACTIVATED; EVEN WITH JEBIM ENTERED INTO THE FLT PLAN AND THAT ONE MUST SELECT AS THE TRANSITION THE IAF; AND NOT 'VECTORS.' ON PREVIOUS GPS APCHS I WAS USUALLY VECTORED; AND WAS UNAWARE OF THIS SOFTWARE CHARACTERISTIC. LOOKING THROUGH THE MANUAL; I CAN'T FIND ANY NOTES REGARDING THIS; BUT IT IS NOW BURNED INTO MY MEMORY. CALLBACK CONVERION WITH RPTR REVEALED THE FOLLOWING INFO: A REVIEW OF THE TRAINING MATERIAL FOR THE INSTALLED NAVIGATION EQUIPMENT CLARIFIED THE PROCEDURES FOR SELECTING AN APCH. THE IAF TRANSITION MUST BE SELECTED AND ACTIVATED.