ATR Oxygen Test

[ATRflyer]

Hi all,

Just wondering if any other ATR drivers out there can answer this one for me. When doing the oxygen test, if the needle on the oxygen pressure gauge on the overhead panel drops back all the way as you press the test button at the mask, what exactly does that mean; even if you get the yellow cross indication at the mask panel and hear the hiss of oxygen as you do the tests ?

From reading some ATR notes available on the web, it says a particular valve is towards the closed position and if you did end up needing to use your oxygen mask in flight, you wouldn't get the right amount or perhaps none at all.

If anyone can clarify on exactly what it means I would be most grateful.
Many thanks,

Atrflyer

[aeroconejo]

from ATR FCOM part 1.07.20....

TEST/RESET pb: this permits a test of oxygen flow without removing the mask from the container. It is springloaded to the RESET position.

TEST: provided MAIN SUPPLY is selected ON, oxygen flows through to the mask. The blinker momentarily displays yellow cross and the flow is audible.


If the main supply is selected OFF you ain't gonna get any oxygen!

hope the above helps

aeroconejo

[ATRflyer]

Thanks aeroconejo for that,

Had a look through the FCOM as well and I guess that if all seems to work okay at the mask it doesn't really matter what exactly happens to the pressure gauge.

Was just wondering though why sometimes the needle moves while doing the test and other times it stays completely still.

Thanks again,
All the best,

Atrflyer

[Captain Stable]

If the valve is closed at the bottle behind F/O's seat, you may still get brief flow, and the needle will drop. This can happen if it has only recently been turned off and there is still residual pressure in the lines. You will get indication on the guage which will drop when you hit the test button on the mask. In order to make sure you have fully checked the system, ensure the valve is open, you have pressure showing, and it doesn't drop (or returns to original indicated pressure) on releasing the test button. Before carrying out the test, have the intercom button on the relevant side depressed, and audio switched to speaker. When you then press the test button you should hear the "whoosh" of oxygen through the speaker. You have now also tested the microphone in the mask, and that mic input switches auto satis.

[Dixons Cider]

Think you wil find the Oxy cylinder is behind the skippers seat there Cap'n Stable

[Captain Stable]

NOT if they switched seats! Okay, okay - that's an "oops!" on my part Thanks for pointing that out!

[ATRflyer]

Thanks a million for that captain stable.

Thats good to know because the few times that it has happened, the gauge returned back to normal almost straight away.

Cheers!!

[Captain Stable]

You are, of course, checking that the switch next to the guage on the overhead panel is on (depressed) and not showing either white "OFF" or amber "LO PR" caption?

[Fropilot]

If the Oxygen pressure needle drops all the way down it is probably because you do not have a full bottle and should check your O2 requiremnets for the flight. Also it could be that the O2 bottle is closed and what you have is residue pressure, I think that is why the FCOM recommends testing the O2 three consecutive times to ensure that they is enough O2 or that the bottle is not closed.