HYD RESERVOIR OVERFILLED; FLUID FORCED BACK PAST CHK VALVE INTO BLEED AIR DUCTS. INFLT; WHEN TURNING ON WING AND STABILIZER HEAT; THE COLLECTED FLUID VAPORIZED BY HOT BLEED AIR CAUSED EXTENSIVE FUMES AND OIL VAPOR IN CABIN AND COATED INSIDE OF WINDSHIELD WITH OIL; OBSCURING VISIBILITY. PF (FO); HAD DIFFICULTY WHEN CAPT APPEARED TO 'FREEZE' TO THE EMER CONDITIONS.

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ON DEC/FRI/95 AT APPROX PST THE LEAR 35 THAT I WAS FLYING EXPERIENCED A RAPID AND LARGE INFLUX OF HYD OIL (MIL-H- 5606) VAPORS AND MIST INTO THE CABIN. FIRST; I WILL DESCRIBE HOW THIS SIT PROGRESSED IN FLT AND SECONDLY I'LL EXPLAIN WHAT APPARENTLY CAUSED IT. WE WERE ON A FLT FROM OUR MAINT BASE IN WENATCHEE; WA; TO OUR OPS BASE IN SEATTLE AT BOEING FIELD. I WAS THE SIC. I AM ALSO FULLY QUALIFIED AS A PIC IN THE ACFT; AND WAS FLYING FROM THE L SEAT. WE HAD 5 PEOPLE ON BOARD. THIS WAS NOT A REVENUE FLT. THE FLT WAS PROCEEDING NORMALLY UNTIL SHORTLY AFTER I BEGAN THE DSCNT INTO BFI. WE HAD BEEN CRUISING AT 16000 FT AND HAD BEEN CLRED DIRECT TO SNOMY INTXN FOR THE CHINS 2 ARR TO BFI. THE FLT CONDITIONS WERE VMC IN LATE TWILIGHT CONDITIONS. THERE WAS A CLOUD LAYER AT ABOUT 11000 FT. AT ABOUT 13000 FT I TURNED ON THE NACELLE HEAT AND A FEW MOMENTS LATER TURNED ON THE WING AND STABILIZER HEAT. THERE WAS A SUDDEN AND LARGE INFLUX OF FUMES AND VAPORS INTO THE CABIN. THE LEAR HAS DEFOG VENTS IN THE WINDSHIELD CTR POST; AND THE VAPORS BILLOWED OUT OF THESE RIGHT INTO OUR FACES. I TURNED OFF THE WING AND STABILIZER HEAT WITHIN SECONDS; BUT THE INFLUX CONTINUED. IN LESS THAN 30 SECONDS THE VISIBILITY IN THE CABIN REDUCED TO LESS THAN 3 FT AND COATED THE INSIDE OF THE WINDSHIELD WHICH COMPLETELY OBSCURED VISIBILITY. IT LOOKED LIKE SMOKE; BUT FORTUNATELY IT WAS NOT DUE TO COMBUSTION. THAT WAS NOT ENTIRELY EVIDENT AT THE TIME; BUT SINCE IT DID NOT SMELL BURNT; I DID NOT THINK WE HAD A FIRE. BUT I DID REALIZE THAT THESE OIL VAPORS WERE PROBABLY EXPLOSIVE; AND THAT THIS WAS A VERY DANGEROUS SIT. THIS NEEDED TO BE HANDLED EXPEDITIOUSLY AND PROFESSIONALLY. WE DONNED OUR OXYGEN MASKS. I REDUCED PWR AND CALLED FOR THE SMOKE AND FUME ELIMINATION CHKLIST. I CONTINUED TO HAND FLY THE ACFT. THE PIC STARTED INTO THE CHKLIST; AND THEN STOPPED. I KNEW THERE WAS MORE TO THE CHKLIST; SUCH AS VENTILATING THE CABIN AND STOPPING THE SOURCE OF THE CONTAMINATION. IT WAS GETTING DIFFICULT TO COMMUNICATE DUE TO THE OXYGEN MASKS AND OIL VAPORS. I TOLD HIM WE NEEDED TO 'DUMP THE CABIN.' HE RESPONDED BY SAYING HE DIDN'T WANT TO DO THAT. I THEN ASKED HIM TO NOTIFY ATC OF OUR PROB. HE REFUSED TO DO THAT ALSO; SAYING 'I AM NOT GOING TO DECLARE AN EMER.' I AGAIN ASKED HIM TO CLR THE CABIN AND HE SAID HE DIDN'T WANT TO MAKE THINGS WORSE. I REACHED OVER AND TURNED THE CABIN HEAT TO MINIMUM (IT WAS ON HIGH); BUT I COULD NOT REACH THE BLEED AIR SWITCHES. I ASKED HIM AGAIN TO CLOSE THE BLEED AIR SWITCHES OR AT LEAST THE R ENG BLEED. HE DID TURN OFF THE R SWITCH. DURING THIS PROCESS I HAD INTERCEPTED THE INBOUND 101 DEG RADIAL TO SEA VOR AND CONTINUED THE DSCNT TO THE ASSIGNED ALT; WHICH I BELIEVE WAS 7000 FT. I FOUND A RAG AND WIPED THE OIL OFF THE WINDSHIELD AS BEST I COULD AND REGAINED SOME VISIBILITY. I NOTICED WE WERE BELOW THE CLOUDS; SO I TURNED OFF THE NACELLE HEAT. NEARING 7000 FT I NOTICED THAT I HAD INADVERTENTLY HELD 300 KTS TO THAT POINT. I BEGAN TO SLOW TO 250 KTS. SOON AFTER THAT THE PIC ACCEPTED A VISUAL APCH. I STILL COULDN'T SEE BFI; BUT COULD IDENT LANDMARKS LEADING TO IT AND AGREED WITH ACCEPTING A VISUAL. I THEN TUNED IN THE BFI ILS BACKCOURSE AND SET THE FLT DIRECTOR FOR THE INTERCEPT; AS A BACKUP. WHEN WE TURNED FINAL I COULD SEE THE ARPT AT ABOUT 7 MI. WE CONTINUED ON IN; ACCOMPLISHED THE NORMAL CHKLISTS AND LANDED. IT HAD BECOME EVIDENT TO ME THAT THE CAPT WAS ABLE TO CONTINUE TO ACCOMPLISH NORMAL COMS AND CHKLISTS; BUT HAD FROZEN UP WITH RESPECT TO TAKING ANY EFFECTIVE ACTION TO DEAL WITH THE EMER. I WAS SERIOUSLY THINKING ABOUT TAKING OVER COMMAND OF THE ACFT; BUT CONTINUED TO TRY TO GET HIM TO TAKE EFFECTIVE ACTION. SINCE HE WAS DOING NORMAL DUTIES AND WAS LUCID; IT WAS EVIDENT HE WAS NOT INCAPACITATED; SO IT WAS NOT CLRLY EVIDENT THAT I SHOULD TAKE OVER COMMAND. IN HINDSIGHT; I SHOULD HAVE TAKEN COMMAND WHEN HE REFUSED TO NOTIFY ATC AND REFUSED TO CLR THE CABIN OF FUMES AS THESE ARE SOP FOR DEALING WITH THIS TYPE OF EMER. THE HYD OIL CONTAMINATIONOF THE ENVIRONMENTAL AND PRESSURIZATION SYS EVIDENTLY WAS CAUSED BY A MISTAKE DURING MAINT PROCS ON THE HYD SYS. APPARENTLY THE HYD RESERVOIR WAS OVERPRESSURIZED AND OVERFILLED WHILE USING A HYD 'MULE.' HYD FLUID WAS FORCED BACKWARDS; PAST A CHK VALVE AND REGULATOR; INTO THE BLEED AIR DUCTS THAT PROVIDE CABIN HEAT AND PRESSURIZATION. INSPECTION HAS SHOWN THAT THE CONTAMINATION WAS EXTENSIVE AND INCLUDED THE EMER PRESSURIZATION VALVES. THE LEAR USES LOW PRESSURE BLEED AIR UNTIL THE ACFT REACHES 29000 FT OR THE WING AND STABILIZER HEAT IS SWITCHED ON; WHICH ACTIVATES THE HIGH PRESSURE BLEED SOURCE. HIGH PRESSURE BLEED AIR IS MUCH HOTTER. THE ADDED HEAT AND VOLUME RAPIDLY VAPORIZED THE HYD OIL IN THE ENVIRONMENTAL SYS; FLOODING THE CABIN WITH FUMES. DURING PREFLT; I HAD NOTICED A PUDDLE OF HYD OIL UNDER THE ACFT AND DRIPPING OIL IN THE EQUIP BAY UNDER THE HYD TANK. I IMMEDIATELY WENT TO THE DIRECTOR OF MAINT AND NOTIFIED HIM OF THE CONDITION. HE SAID HE WAS NOT SURPRISED AND THAT THEY HAD SPILLED SOME OIL DURING A MAINT PROC. I ENQUIRED FURTHER AND HE SAID IT WAS A MISTAKE THAT HAPPENED DURING GEAR RETRACT TESTS AND HE ASSURED ME THAT THE HYD SYS WAS NORMAL AND THE ACFT WAS AIRWORTHY. I INFORMED THE PIC OF THE SIT; HE TOOK NO ACTION THAT I COULD SEE; INCLUDING NOT LOOKING IN THE EQUIP BAY. I HAVE FULLY RPTED THESE EVENTS TO OUR SEATTLE BASE LEAD PLT AND TO THE DIRECTOR OF OPS. I REMINDED HIM THAT FARS REQUIRE A MAINT RELIABILITY RPT WITHIN 24 HRS. I INCLUDED SPECIFIC CONCERNS ABOUT THE CONDUCT OF THE PREFLT; THE ACTIONS INFLT AND POST FLT FOLLOW-UP BY THE CAPT. IN CRM TRAINING THAT I HAVE RECEIVED; THE PROB OF INCAPACITATION IS ADDRESSED. UNFORTUNATELY; THIS WAS NOT THAT CLR. AS MENTIONED PREVIOUSLY; THE CAPT WAS STILL LUCID. HE WAS ACCOMPLISHING NORMAL TASKS. IT IS EVIDENT THAT HE FROZE UP IN REGARDS TO TAKING ANY EFFECTIVE ACTION TO DEAL WITH THE EMER. ESTABLISHED PROCS WERE DELIBERATELY NOT FOLLOWED; AND I BELIEVE THAT I WAS REMISS IN NOT TAKING COMMAND OF THE ACFT. HE EITHER DIDN'T RECOGNIZE THIS AS BEING AN EMER OR WAS AFRAID TO ACT. HE SHOULD HAVE IMMEDIATELY DECLARED AN EMER SO AS TO HAVE EVERY POSSIBLE RESOURCE IN OUR FAVOR. THIS WOULD HAVE INVOKED THE AUTH TO DEVIATE FROM REGS AS NECESSARY TO DEAL WITH THE EMER; AND WOULD HAVE DONE ALL THAT WAS POSSIBLE TO ENSURE THE SAFETY OF ALL CONCERNED. FORTUNATELY; WE LANDED SAFELY AND THERE WERE ONLY MINOR INJURIES DUE TO THE CHEMICAL EXPOSURE.