CORP JET HAS INVERTER FAILURE LIGHT ACTIVATE. THIS CTLS PRIMARY FLT INSTS AND PRESSURIZATION. EMER DSCNT.

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WHILE CRUISING AT FL430 WE EXPERIENCED A #1 INVERTER FAILURE. BECAUSE WE WERE FLYING INTO THE SUN; WE DID NOT IMMEDIATELY SEE THE INVERTER FAIL LIGHT. THE #1 INVERTER CTLS; AMONG OTHER THINGS; THE PLT'S FLT INSTS AND PRIMARY PRESSURIZATION. WE WERE DEALING WITH THE PRESSURE PROB BY DONNING OUR OXYGEN MASKS AND STARTING A DSCNT AFTER SO ADVISING ATC. ATC TOLD US NOT TO DSND BECAUSE THERE WAS TFC IMMEDIATELY BEHIND US AT FL410. I TRIED TO PREVENT THE CAPT FROM DSNDING IMMEDIATELY BUT WAS UNSUCCESSFUL AND ATC DIVERTED THE OTHER ACFT. WHILE ALL OF THIS WAS GOING ON; MY OXYGEN MASK MIKE WOULD NOT FUNCTION AND I HAD TO REMOVE MY MASK ON SEVERAL OCCASIONS TO TALK INTO A HAND MIKE. THIS; OF COURSE; RESULTED IN MY BECOMING QUITE HYPOXIC. AS A RESULT; I WAS VIRTUALLY USELESS AS A COPLT DURING THIS PHASE OF FLT. AT APPROX FL350; ATC ASKED IF WE WANTED TO DECLARE AN EMER AND WE REPLIED IN THE AFFIRMATIVE. ATC THEN DIVERTED US TO FRESNO SINCE IT WAS THE CLOSEST ARPT. BY THE TIME WE WERE DOWN TO 14000 FT; I HAD TURNED ON THE STANDBY INVERTER AND HAD RECOVERED THE USE OF THE PLT'S INSTS AND PRIMARY PRESSURIZATION. THE PRIMARY CAUSE OF THE PROB WAS THE FAILURE TO IDENT THE CAUSE OF THE PROBS FACING US AS BEING AN INVERTER FAILURE AND THE FAILURE TO USE APPROPRIATE CHKLISTS CAUSED BY HYPOXIA. THE BEST SOLUTION TO THIS PROB WOULD BE AN ONGOING TRAINING PROGRAM TO KEEP THESE PROCS FRESH IN OUR MIND IN ADDITION TO A ONCE A YR TRIP THROUGH FLT SIMULATOR TRAINING.