A LEAR 60 IN CLB AT FL180 DISCOVERS CREW OXYGEN NOT AVAILABLE DUE TO BOTTLE SHUTOFF VALVE NOT OPENED AFTER SVCING.

Narrative

UPON ARR AT ZZZ; US; I; AS THE CAPT; CHKED OUR CAN (IE; ACFT FLT LOG) TO MAKE SURE THAT THE PREVIOUS DAY'S MAINT WORK WAS DONE PROPERLY AND SIGNED OFF CORRECTLY IN ACCORDANCE WITH OUR MAINT MANUAL. MEANWHILE; MY COPLT WAS PERFORMING PREFLT CHKS ON THE ACFT BEFORE WE FLEW THE DAY'S FLT. THE DISCREPANCY WAS THAT OUR OXYGEN SYS NEEDED TO BE TOPPED OFF TO REMAIN IN THE REQUIRED LIMITS. WHEN THE MECH FILLS THE OXYGEN SYS THEY MUST TURN OFF THE OXYGEN FLOW TO THE CREW AND THE PAX MASKS. THEN AFTER THE OXYGEN IS TOPPED OFF; THE MECH WOULD OPEN THE VALVE AND ONCE AGAIN PAX OXYGEN WOULD BE AVAILABLE TO PAX AND CREW. AFTER CONFIRMING THAT THE WRITE-UPS WERE CORRECT; I ASKED MY COPLT IF THE PREFLT HAD BEEN ACCOMPLISHED. HE STATED THAT IT WAS AND WE PREPARED TO LEAVE. AFTER TKOF WE WERE CLRED TO FL180. UPON REACHING FL180; I; AS THE PNF; PROCEEDED TO ACCOMPLISH THE TRANSITION LEVEL CHKLIST. WHEN DOING THIS; A VISUAL CHK OF THE OXYGEN PRESSURE GAUGE AS WELL AS THE CHKING OF THE CREW OXYGEN MASK IS REQUIRED. I DID THIS AND DID NOT RECEIVE A POSITIVE FLOW OF OXYGEN TO MY MASK. THE COPLT CHKED HIS AND AGAIN RECEIVED NO OXYGEN PRESSURE. THUS WE REQUESTED A LOWER ALT WHICH WAS GIVEN TO US. I ASKED THE COPLT IF HE HAD PERFORMED THE PREFLT CHK WHICH REQUIRED HIM TO TEST BOTH CREW MEMBER OXYGEN MASKS. HE SAID HE THOUGHT HE HAD; BUT IT WAS OBVIOUS HE HAD NOT. THE REASON FOR THIS HE TOLD ME WAS HE WAS DISTR BY THE GND CREW WHO WERE BRINGING BEVERAGES AND ICE TO THE ACFT. THERE WAS NO ATC PRIORITY GIVE TO US AND A DIVERSION WAS MADE TO ANOTHER ARPT IN WHICH MAINT WAS PERFORMED ON THE ACFT (IE; THEY OPENED THE NOSE PANEL AND TURNED ON THE OXYGEN). I BELIEVE THE MAIN CAUSE OF THE PROB WAS THE DISTR TO THE COPLT BY GND PERSONNEL ALLOWING HIM TO MISS THE ITEMS REQUIRING HIM TO CHK THE MASKS. THIS LEAR 60 HAS A NOSE COMPARTMENT OXYGEN SYS VERSUS A TAIL LOCATED OXYGEN SYS. THE MAIN REASON I MENTION THIS IS BECAUSE IN A NOSE COMPARTMENT LOCATED OXYGEN SYS THE OXYGEN INDICATOR WILL READ THE OXYGEN BOTTLE PRESSURE -- EVEN IF THE VALVE IS TURNED OFF AND THE CREW MASKS ARE TESTED. WHEREAS; IN THE TAIL LOCATED OXYGEN SYS; WHEN YOU TEST THE MASK; THE COCKPIT OXYGEN INDICATOR WILL READ ZERO IF THE VALVE IS TURNED OFF. WHEN I BOARDED THE ACFT TO PREPARE FOR TKOF; I LOOKED AT THE OXYGEN INDICATOR AND IT SHOWED A NORMAL OXYGEN LEVEL. I; HOWEVER; DID NOT TEST MY MASK ON THE GND; BECAUSE THAT WAS PART OF THE COPLT'S PREFLT CHKS. I LEARNED FROM THIS THAT; AS A CAPT; AFTER MAINT HAS BEEN PERFORMED; TO PAY PARTICULAR ATTN TO THE SYS BEING WORKED ON AND I SHOULD DOUBLECHK MY COPLT'S ACTIONS. I BELIEVE THAT EACH CREW FLYING THE LEAR 60 SHOULD KNOW WHERE THEIR OXYGEN SYS IS LOCATED AND ITS OPERATIONAL CHARACTERISTICS. AT OUR COMPANY WE HAVE OVER 30 LEAR 60 ACFT WITH BOTH SYS. IT IS NOW A COMPANY POLICY FOR BOTH CREW MEMBERS TO CHK THE CREW OXYGEN MASKS. SUPPLEMENTAL INFO FROM ACN 482316: WE BOTH WERE CONCERNED WITH THE APCHING TSTMS. WE PICKED UP CLRNC PROGRAMMED FMS; AND DEPARTED WBOUND FOR HAYDEN; CO. AN IMMEDIATE DSCNT TO 12000 FT WAS MADE. FLT CONTINUED TO DENVER. ACFT SVCED BY TURNING ON KNOB TO OXYGEN BOTTLE AND FLT CONTINUED TO HAYDEN.