GA SMA ALT DEVIATION EXCURSION FROM CLRNC ALT.

Narrative

IFR CROSS COUNTRY; CAK TO UIZ; MICHIGAN PROB OF MISSING XMISSIONS FROM DET APCH CAUSED BY SWITCHING #2 RADIO FOR UNICOM AT BERZ-MACOMB ARPT (DEST). INADVERTENT SELECTION OF #2 XMITTER WAS CORRECTED AFTER ABOUT 5 MINS WHEN #1 XMITTER WAS SELECTED AND SUBSEQUENT CONTACT RE-ESTABLISHED WITH DET APCH. DURING THE TIME WHILE OFF FREQ; SERIOUS WINDSHEAR AND SNOW SHOWERS WERE ENCOUNTERED CAUSING LOSS OF ALT TO 4000' MSL (5000' MSL ASSIGNED BY ATC). LATER WHILE BEING VECTORED BY ATC; LOST ALT TO 3000' MSL DUE TO WINDSHEAR/SNOW SHOWERS. VERY DIFFICULT TO HOLD ALT IN WX CONDITIONS. ELECTED TO LAND AT DETROIT CITY RATHER THAN UIZ. BEFORE LNDG AT DETROIT CITY; DID EXPERIENCE WINDSHEAR ENCOUNTER RESULTING IN A DSCNT TO 2500' (WHILE ASSIGNED 3000' MSL BY ATC). SOME ALT DEVIATION MAY HAVE BEEN CAUSED BY INATTN TO ALT WHILE BEING PREOCCUPIED BY PROSPECTS OF AIRFRAME ICING. SOME SERIOUS RESERVATIONS ABOUT WINTER FLT INTO IMC CREATED SOME STRESS UPON PLT. FLT UNDERTAKEN UPON INSISTENCE BY MALE PAX. MOST HELPFUL ACTION: NEVER; NEVER INITIATE A FLT WHICH THE PLT DOES NOT FEEL ADEQUATE TO SAFELY COMPLETE.