AN MD90 FO FAILS TO DON THE SUPPLEMENTAL OXYGEN MASK WHEN THE CAPT LEFT THE COCKPIT DURING FLT AT FL260 WHILE S OF LAS; NV.

Narrative

ON APR/XA/01; I WAS FLYING ROTATION; XYZ; AS PART OF MY IOE. ON FLT FROM SLC TO SAN; I WAS ACTING AS FO; PF. FAA AVIATION SAFETY INSPECTOR OUT OF SLC WAS RIDING THE JUMP SEAT. AT APPROX XA20Z CAPT LEFT THE COCKPIT TO USE THE LAVATORY. AS SOON AS THE CAPT LEFT HIS SEAT I BEGAN USING SUPPLEMENTAL OXYGEN BY HOLDING THE MASK TO MY FACE. THE CAPT RETURNED TO HIS SEAT 2-3 MINS LATER; AT WHICH TIME I DISCONTINUED USE OF SUPPLEMENTAL OXYGEN. IT WAS AT THIS TIME FAA INSPECTOR INQUIRED ABOUT MY USE OF SUPPLEMENTAL OXYGEN. IT WAS MY UNDERSTANDING THAT I WAS IN FULL COMPLIANCE WITH ALL ACR POLICIES AND APPLICABLE FARS. SUPPLEMENTAL INFO FROM ACN 509075: MY FO PULLED OUT HIS OXYGEN MASK AND HELD IT IN HIS LAP; WAITING FOR THE INSPECTOR TO UNSTRAP; VACATE THE JUMP SEAT AND OPEN THE COCKPIT DOOR. AS I STARTED TO LEAVE THE SEAT I SAW THE FO RAISE THE OXYGEN MASK TOWARD HIS FACE. I THEN TURNED MY ATTN TOWARD THE INSPECTOR TO FOLLOW HIM OUT OF THE COCKPIT. THE FO HAD PUT THE OXYGEN MASK TO HIS FACE BUT HAD NOT PUT THE HARNESS OVER HIS HEARD. I HAD NOT NOTICED THAT THIS WAS THE CASE. THE FO WAS FAIRLY NEW WITH THE COMPANY. OUR COMPANY MANUALS SAY TO DON THE OXYGEN MASK. SEEMS LIKE MAYBE THE MEANING OF 'DON' WAS MISINTERPED.