ALTDEV ALT OVERSHOT.

Narrative

CLRNC WAS MUSL 5 DEP; MUSL; RADAR VECTORS TO SANTA CATALINA 084 DEG RADIAL; SANTA CATALINA; DIRECT LAX; DIRECT GORMAN; AS FILED; MAINTAIN 5000 FT; EXPECT FL310 10 MINS AFTER DEP. ON DEP; TALKING TO SOCAL DEP PRIOR TO REACHING 5000 FT CLRED 'TO MAINTAIN 16000 FT; EXPEDITE CLB THROUGH 10000 FT. CLBING OUT OF 6700 FT CLRED TO 'AMEND ALT; MAINTAIN 8000 FT.' ACFT WAS CLBING AT 5500 FPM WITH THE AUTOPLT ENGAGED. SELECTED VERT SPD MODE TO SLOW RATE OF CLB; BUT BY NOW (GOING THROUGH 7100 FT) ALT ACQUIRE MODE WAS ENGAGED AND AIRPLANE CONTINUED TO CLB AT 5000 FPM WASN'T SURE IF AUTOPLT WAS CAPABLE OF LEVELING OFF AT THIS RATE OF VERT SPD; SO WATCHED TO SEE. AT 7700 FT IT BECAME APPARENT IT WAS NOT CAPABLE; SO I DISCONNECTED THE AUTOPLT AND MANUALLY LEVELED AIRPLANE OFF AT A RATE SO AS NOT TO RAISE THE PAX 'UP TO THE CEILING.' CLB WAS STOPPED AT 8;350 FT. I QUERIED THE CTLR IMMEDIATELY AFTERWARDS ABOUT AIRPLANE CAPABILITY WITHIN 1000 FT OF ASSIGNED ALT AT EXISTING VERT SPD OF (5500 FPM). HE ACKNOWLEDGED FAULT AND APOLOGIZED FOR THE CLRNC. CTLR IMMEDIATELY THEN CLRED US BACK TO MAINTAIN 16000 FT. THE LIMITATION THAT THIS AUTOPLT DEMONSTRATED IS NOT SOMETHING THAT IS 'PUBLISHED.' ONE ONLY LEARNS OF IT THROUGH EXPERIENCE. HAD I EXPERIENCED THIS 'DEMONSTRATION' AT AN EARLIER TIME I WOULD HAVE DISCONNECTED THE AUTOPLT AT 6700 FT. LIVE AND LEARN! NOT A 'NORMAL' SIT. NOR A NORMAL CLRNC.