Medium Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Training / Qualification
Aircraft Equipment Problem Critical
General Maintenance Action
Procedure; Human Factors; Company Policy; Aircraft
Arrived at aircraft approximately 40 minutes prior to departure time.   During preflight checklists; the First Officer mentioned that he had not seen the Eros oxygen system installed on subject aircraft (he has been out on Mil leave (off and on) for many years). I offered to give him a quick tutorial as I was familiar with the system from my days on the [Boeings].  I grasped the red handles on the mask and removed it from the compartment and said; 'The retention band will inflate to allow donning.' The retention band did not inflate. I was unable to breathe from the mask. I asked him to check his mask to see if he had similar results; which he did. No oxygen to either mask; we were both 'sucking vacuum' while trying to inhale.  Oxygen pressure at the bottle was 1;750 PSI (full) and the valve was safety-wired.  When Maintenance arrived they determined the valve had indeed been safety-wired; but in the CLOSED position. They opened the valve and found it to be leaking; ordered a new bottle; but had to leave because their shift was ending.  When the second Mechanic arrived with the new bottle he determined the regulator was also leaking; so that had to be ordered too. Full repairs were accomplished; the system ops checked; and we departed not quite 2 hours late. Ensure Maintenance and cockpit crews follow published procedures when servicing and pre-flighting the cockpit oxygen system; even in jets with the Eros O2 system installed.  The Eros O2 system is not taught in ground school and is not present in simulators when we return for our training. There is no video online demonstrating the proper use of the system. As such; it is understandable that most/all crews have little or no idea how the system works.  The proof lies here: This aircraft may have flown for over a month with no oxygen supplied to the cockpit masks. None. Add in a pressurization problem (which is becoming more common on the fleet) and you have a recipe for; well; you know.   The first AMT (Aviation Maintenance Technician) to service the aircraft searched his tablet computer and did not find any oxygen service for at least 31 days. As luck would have it; I flew the same aircraft today and did a thorough logbook review enroute. The physical logbook entries were dated back to [early] NOV and indicated no O2 service during the period.
Air carrier Captain reports discovering during preflight that the crew oxygen system is not functional. Maintenance discovers that the valve is turned off and safety wired in that position; and had likely been that way for over a month. The Captain believes that the late discovery is the result of no training on how to preflight the system.