C172 PLT DSNDS BELOW MSA IN A POPULATED AREA DUE TO DISTR WITH RADIO; AIRSPD; AND RETRIEVAL OF A CHART.

Narrative

I DEPARTED LVK AFTER A TOUCH-AND-GO AND DEPARTED STRAIGHT OUT WITH THE INTENTION TO CLR THE LVK CLASS D AIRSPACE AND THEN TURN N AND FOLLOW THE HWY TO CONTINUE MY FLT. AS I WAS CLBING OUT AT ABOUT 1200 FT MSL; I REDUCED PWR TO SLOW MY SPD A BIT IN ORDER TO GET MY MAP OUT; CHANGE RADIO FREQS; AND PREPARE FOR MY TURN N. ONCE OUTSIDE OF THE LVK CLASS D AIRSPACE; AS I MADE THE TURN N OVER THE FREEWAY; I REALIZED I HAD ACTUALLY DSNDED TO 900 FT MSL AS A RESULT OF THE REDUCTION IN PWR AND MY FAILURE TO CORRECTLY SET UP AND TRIM THE PLANE TO COMPENSATE FOR THE PWR CHANGE. I IMMEDIATELY APPLIED FULL PWR AND RETURNED TO A MAX RATE OF CLB AND CONTINUED UP TO 2500 FT MSL. AN ALT OF 900 FT MSL ABOVE THAT AREA COULD EASILY BE CONSIDERED FLYING BELOW MSA'S. THE CONTRIBUTING FACTORS TO THIS SIT INCLUDED THE DISTR OF FOCUSING ON THE MAP AND CHANGING RADIO FREQS AS WELL AS MY FAILURE TO PAY ATTN TO MY ALT AND CLB RATE AFTER REDUCING PWR. I DISCOVERED THE PROB AS I TURNED TO THE N AND SCANNED MY GAUGES.