C-525 SINGLE PLT DEPARTS WITHOUT TWR CLRNC.

Narrative

IN BEING CLRED FOR TKOF -- OR SO I BELIEVED -- PROCEEDED INTO 'POS AND HOLD' AND DID NOT REMAIN; CONTINUED TO TAKE OFF. I HAD A BOUT OF FOOD POISONING THE PREVIOUS DAY. SINGLE PLT IN A CPR OP. I HAD CANCELED FIRST FLT OF MY CAREER DAY PREVIOUSLY DUE TO ILLNESS AND DECIDED; ALTHOUGH NOT 100%; TO MAKE A PLANNED FLT ON THIS DAY. WE HAD LANDED JUST 15 MINS EARLIER AND WERE DROPPING PAX ENRTE TO BOISE. I ELECTED TO CLB VFR. THE CTLR HAD SPECIFIED MAINTAIN VFR BELOW FL180. ON THE WAY IN; CEILINGS WERE PREVALENT AT AROUND 14000-15000 FT. AS I TOOK THE RWY; IT WAS ON MY MIND AS TO WHETHER I WOULD BE ABLE TO MAINTAIN THE CLOUD CLRNC/VFR UP TO FL180. BEING FAMILIAR WITH AREA; I WAS AWARE OF TERRAIN. I THEN DEPARTED; UNSURE AFTER DEP AS TO MY CLRNC TO TAKE OFF. THAT DAY; I HAD ELECTED TO MAKE A FLT WHEN I WAS NOT COMPLETELY WELL. AS I RARELY GET SICK; I HAD NO IDEA HOW LONG RECOVERY WOULD TAKE. AS FOR PROCS; I NOW USE THE PITOT HEAT SWITCH AS AN INDICATION THAT I AM CLRED FOR TKOF. THE ANNUNCIATOR PANEL ON THE CJ2 EXTINGUISHES WHEN WE TURN ON PITOT HEAT.