Hi I was looking at a real 767 checklist and I noticed the Before Start Checklist has a "Oxygen........Checked" on it. How is this performed on the real aircraft? Do they wear the mask for a moment and test it or do they press some test switches on it without wearing the mask? Also are the mask located on the lower left and lower right of the pilot and copilot? Thank You.:-)

Hi "November"Lufthansa crews check the operation of the oxygen masks by wearing them. They also check the oxygen quantity. On the 767/744, this information is found on the Status page of the EICAS system.

Hi you say on the status page? guess the PIC EICAS was not simulated 100% because the lower EICAS screen does not show this.:-doh

Yupp, the same page as where the flight controls are displayed.As I am not at my PIC PC, I can not check whether or not the indication is simulated on PIC.

In the 767 the check is simply to push the red 'test' switch and observe a yellow indication in a normally black window, and hear the oxygen flowing.At the same time as this you switch the mic selector to 'oxy' and hear the air noise through the speakers to ensure the speaker in the mask is working.(Taking the mask out to check it sounds like a lot of work! it normally takes me 5 mintues to re-stow those things!)

"guess the PIC EICAS was not simulated 100% because the lower EICAS screen does not show this."I'd say it was a simple case of it being too much bother to simulate considering the number of times it would be used, November. The pressure value displayed on the EICAS is not a constant value, even if the crew don't use/test the masks. The temperature of the area where the crew bottle is stowed varies greatly (despite the bottle being in a pressurized area of the aircraft). Pressure variations due to temperature changes can be over 100psi. When the crew oxygen bottle is "full", the pressure should be around 1850 (at a specific bottle temperature). However, the Minimum Equipment List usually allows the aircraft to depart with much lower pressures, depending on the number of the crew in the cockpit. Considerations must be made, however, for flights over mountainous areas where, after a rapid cabin depressurization, it may not be possible for the aircraft to descend to an altitude where the air is breathable (without oxygen). Because of this, the new Airways over China require special consideration.The pic below shows oxygen pressure (as well as the optional display of brake temperature)http://www.ozemail.com.au/~iriddell/767/LowerEicas.JPGThis particular aircraft has no reading for passenger oxygen pressure because the passengers use oxygen produced by mixing two chemicals together. The chemicals are held in a small canister above the passengers heads (Some aircraft have canisters in the seat backs). This chemical generation system seems to be very popular on the 767. I believe some degree of weightsaving is achieved by doing it this way.For the scientists amongst us, oxygen is generated chemically by mixing sodium chlorate and iron. NaClO3 + Fe = NaCl + FeO + O2 (that is, salt, Iron Oxide(rust) and Oxygen). A cautionary note for engineers working on this system: This chemical reaction can produces canister surface temperatures of up to 232 degrees!Cheers.Ian.