C560 FLT CREW HAS SMOKE IN CABIN AND DIVERTS FOR LNDG.

Narrative

APPROX 10 MILES E OF PALMDALE VORTAC A PAX CAME TO THE FRONT AND INFORMED US THAT THERE IS SMOKE IN THE BACK. AFTER VISUALLY CONFIRMING THE EXISTENCE OF WHITE SMOKE I RECOMMENDED TO THE CAPT TO DECLARE AN EMER AND REQUEST VECTORS BACK TO VNY. AT THAT TIME THE SMOKE REACHED THE COCKPIT. I PUT MY OXYGEN MASK ON; AND PULLED OUT THE EMER CHKLIST. I ASKED THE CAPT IF HE WANTED ME TO DECLARE AN EMER; HE TOLD ME 'NOT YET.' HE DECIDED TO RETURN TO VNY. COMPLETING THE EMER CHKLIST; WE DUMPED THE CABIN AS THE CHKLIST REQUIRED; AND MANUALLY DROPPED THE PAX MASKS. AFTER WE DUMPED THE CABIN PRESSURE; THE SMOKE CLRED; WE RETURNED TO VNY WITH NO FURTHER INCIDENT. SUPPLEMENTAL INFO FROM ACN 705026: WE DEP FROM VNY ARPT ON A PART 135 FLT. SHORTLY AFTER CROSSING PALMDALE AND STILL IN OUR CLB; ONE OF THE PAX APCHED THE CREW AND CLAIMED THE CABIN TEMP WAS UNUSUALLY HIGH. I RESPONDED BY SAYING THAT WE WERE WORKING ON THE SITUATION. I TURNED THE TEMP CTLR TO 'MANUAL' POSITION AND TO 'COLD.' BY MONITORING THE CABIN TEMP GAUGE; I NOTICED THAT IT WAS READING ABOUT 100 DEGS. ABOUT FIVE MINS LATER I LOOKED BACK AND SAW A WHITISH COLORED SMOKE RESEMBLANCE IN THE CABIN. I WAS UNSURE WHETHER IT WAS REAL SMOKE OR JUST COLORED MOISTURE FROM THE AIR CYCLE MACHINE. I IMMEDIATELY REQUESTED THE COPLT TO INITIATE THE SMOKE REMOVAL CHKLIST AS A PRECAUTION; IN CASE REAL SMOKE EXISTED. SIMULTANEOUSLY WE REQUESTED ATC TO RETURN BACK TO VNY ARPT. SOON AFTER THAT WE GOT INSTRUCTIONS TO TURN RIGHT BACK TOWARDS PALMDALE AND DSNDED DOWN TO FL200. DURING OUR DSCNT; ATC GAVE US LOWER ALT AND AS SOON AS I HAD VNY ARPT IN SIGHT; WE CANCELLED THE IFR FLT PLAN AND CONTINUED DIRECTLY TO THE ARPT UNDER VFR. OUR ALT AT THIS TIME WAS CLOSE TO 16000 FT MSL. THE TIME AND POINT AT WHICH WE INITIALLY TURNED AROUND FOR OUR RETURN BACK TO VNY; WE WERE AT AN ALT OF FL250; AND CLBING. SO WITH REGARDS TO LOSING ALT OR AVAILABLE DISTANCE; IT FELT EASIER TO GO STRAIGHT BACK TO VNY; WHICH WOULD RESULT IN THE SMOOTHEST AND EASIEST DSCNT PATH. DURING THE EXECUTION OF THE SMOKE REMOVAL CHKLIST; WE HAD THE PAX MASKS DROP AND THE EMER DUMP VALVE OPENED; WHICH RELAXED THE PAX. AND WE LANDED THE ACFT SAFELY BACK IN VNY.