SINGLE PLT OF A C525 FAILS TO FOLLOW PROPER FLT PATH ON CHANL DEP FROM SNA. ALSO OVERSHOOTS INITIAL ALT.

Narrative

THE ACFT IS EQUIPPED WITH A SPZ-5000 AUTOPLT COUPLED TO A KLN 900 GPS. PRIOR TO TKOF; I SET UP THE ASSIGNED SID; CHANL1.GMN DEP WITH ASSIGNED ALT. THE VISUAL PICTURE OF THIS DEP DISPLAYED ON EHSI VISUALLY APPEARED TO MATCH THE DEP PICTURED IN THE CURRENT FAA APCH BOOK. UPON TKOF; I IMMEDIATELY ENGAGED THE AUTOPLT COUPLED TO THE KLN 900. THE ACFT CORRECTLY FLEW THE DEP AS DEPICTED ON THE EHSI. WHEN INSTRUCTED TO DO SO BY SANTA ANA TWR; I CONTACTED SOUTHERN CALIFORNIA DEP. ABOUT ONE MINUTE LATER; THE CTLR ASKED ME MY HDG. IT APPEARED TO BE ABOUT 200 DEGS. THE CTLR THEN INFORMED ME THAT I WAS SUPPOSED TO HAVE TAKEN A HDG OF 175 DEGS ON DEP AND GAVE ME A NEW HDG TO CORRECT FOR THE ERROR; AN ERROR WHICH APPEARS TO BE BUILT INTO THE COMMERCIAL DATABASE ON THE KLN 900. I DISENGAGED THE NAVIGATION PORTION OF THE AUTOPLT AND WENT OVER TO HDG MODE. HOWEVER; THE ACFT CONTINUED TO CLB AND I DID NOT PERCEIVE THIS FACT UNTIL WE HAD EXCEEDED THE ASSIGNED ALT BY OVER 200 FT. THE CTLR THEN GAVE ME A NEW HDG AND NEW ALT WITH WHICH I COMPLIED IMMEDIATELY. THERE WERE NO FURTHER PROBS FOR THE BALANCE OF THE FLT. PLTS MAY INCORRECTLY ASSUME THAT GPS COUPLED DEPS ARE CORRECT WHEN THEY APPEAR IN THE COMMERCIAL DATABASE AND A SOPHISTICATED NAVIGATIONAL INSTRUMENT LIKE THE KLN 900. THE COMPLEXITIES OF FLYING IN THE SOUTHERN CALIFORNIA AIRSPACE REQUIRE CONSIDERABLE ATTENTION OUTSIDE THE ACFT; PARTICULARLY WHEN FLYING SINGLE PLT. THE DEMANDS OF AIRSPACE AWARENESS STRONGLY SUGGEST THE USE OF FULLY AUTOMATED; COUPLED GPS DEPS. HOWEVER; THE COMBINATION OF THE KLN 900 AND THE COMMERCIAL CARTRIDGE DATABASE DO NOT APPEAR TO PROVIDE DEP PROCS CONSISTENT WITH PUBLISH DEPS. IT MIGHT BE PRUDENT TO REQUIRE COMMERCIAL DATABASE PROVIDER TO POST TO THE VISUAL SCREEN; ON EACH GPS DEVICE FOR WHICH THEY PROVIDE DATA; A WARNING SAYING THAT THE DATABASE DEP DOES NOT COINCIDE WITH PUBLISHED DEPS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT IT WAS HIS BELIEF THAT THE DATABASE AND DISPLAY OF THE GPS/FMS ON HIS ACFT DO NOT PROVIDE A PROPER PRESENTATION OF PUBLISHED DEPS WITH 'CONDITIONAL' LEGS; IE; LEGS THAT ARE OTHER THAN FROM ONE DISTINCT GEOGRAPHIC WAYPOINT TO ANOTHER. THESE INCLUDE 'HDGS AND/OR RADAR VECTORS' TO INTERCEPT SUBSEQUENT LEGS AND TRACKS TO A GIVEN ALT WITH SUBSEQUENT TRACK CHANGES DEPENDENT ON REACHING SUCH ALT. HE BELIEVES THAT IF THE SYSTEM LIMITATIONS PRECLUDE PRECISE NAVIGATIONAL PERFORMANCE BY AUTO FLT; THESE DEPS AND/OR SIMILARLY DEFICIENT ARRS SHOULD EITHER BE EXCLUDED FROM THE DATABASE OR FLAGGED IN SOME MANNER TO WARN THE PLT THAT SUCH PROCS SHOULD BE FLOWN VIA MODES OTHER THAN AUTOFLT EITHER BY AUTOPLT OR MANUALLY.