ACR PIC COMPLAINS OF HIS MLG ACFT PERFORMANCE CAPABILITIES AT CERTAIN WTS WITH REF TO HIGHER ALTS AND ALLOWABLE G FORCE CTL LIMITS. ALTDEV ALT EXCURSIONS TO CTL AIRSPD DEVS IN MOUNTAIN WAVE.

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ENRTE CRUISE MSP TO PHX; FL350; CLR. RPTED SOME MOUNTAIN WAVE ACTIVITY EARLIER IN DAY. GROSS WT 112000 LBS. SMOOTH RIDE FOR APPROX 45 MINS THEN ENCOUNTERED LIGHT MOUNTAIN WAVE; NO PROB. SUDDENLY ENCOUNTERED MODERATE TO SEVERE MOUNTAIN WAVE. PAX PREVIOUSLY STRAPPED IN. UNABLE TO MAINTAIN AIRSPD WITHIN LIMITS DESPITE GROSS THROTTLE CORRECTIONS. HAD TO CLB 500 FT TWICE DUE TO EXCESS SPD; NOTIFIED ATC! GOT BLOCK ALT FL350-FL360 AND REQUESTED EARLIEST DSCNT. DSCNT ACCOMPLISHED. RIDE IMPROVED RAPIDLY AS MOUNTAIN WAVE DIMINISHED. THIS IS THE SECOND TIME GOING TO ALT BELOW THE 1.5 G MARGIN HAS BITTEN ME. OUR CHARTS INDICATE 105000 LBS FOR 1.5 G AND 130000 LBS FOR 1.25 G PROTECTION AT FL350. THIS ACFT'S WING DOES NOT BELONG UP AT ALT AT THE 1.25 G LIMIT WT. THE MARGIN (HIGH/LOW) IS TOO SMALL. IT IS UNSAFE! MANY PLTS DO IT TRYING TO SAVE FUEL. MISTAKE! THE FAA AND THE COMPANY NEED TO CORRECT THIS SIT. NOTE: THE MLG AUTO THROTTLES ARE USELESS IN TURB. YOU MUST IMMEDIATELY GO TO MANUAL THROTTLES AS THE ACFT ALWAYS WANTS TO OVERSPD.