Aircraft Checkout on stand

[radio ears]

Is it normal to check out the emergency oxygen pressure masks on the stand in the view of the Pax waiting in the terminal?

[Jet II]

Yes is the short answer.

As part of the pre-flight check the Oxy masks have to be checked - as the a/c is usually parked at the gate when the crew get on board, there is no option but to do it then.

The crew cannot wait until the aircraft has pushed - back as they are too busy at that moment and the rules say that the check must be done prior to a/c moving.

:D

[Departures Beckham]

When you say they are tested, do you mean they are actually dropped or is there just a system check.

I presume that the covers are held closed by electro-magnet so that in the event of a power failure they drop automatically, is this correct?

One more, typically how much oxygen (in terms of time for a full load of pax) does an aircraft hold? I presume it only needs enough to decend to a lower altitude and can then use the ourside air.

[Tiger]

The paxs oxygen drop out masks aren`t checked daily. It would take for ever to restow every mask.


The length of time the oxygen lasts for depends on a/c type and what type of system they use. The newer a/c use a chemical generator which last between 12-15 mins on short haul aircraft, while EOPS 757 lasts 22 mins. There is one generator located above each row of seats each side with either 3 or 4 masks attached, if 3+3 seating. Pulling one mask in that row activates the flow to all the masks in that row ie the A B C or D E F side.
So it does not matter how many paxs are on board the a/c.

Older aircraft (DC9) for example had large tank in the hold.

The system works in a number of ways but on the whole they drop automatically now days with the drop in cabin pressure(except early 146??). When they do drop its very noisy with all the compartment doors opening. The pilots also have a manual backup to make sure the masks drop which they will activate. Also once the aircraft has levelled out and the command by the Capt/FO says it OK the cabin crew will carry out checks and also drop any masks from the PSU as neccessary.

The most usual decompression is a slow one, where the masks will drop and paxs don`t realise anything is wrong...they can still breathe so they just look at the mask and carry on with there in flight meal, drink or reading The Times.

[Jet II]

Don't get confused between PAX oxygen and Flight Crew - the checks the flight crew do prior to the flight is only on the crew oxygen system - each crew position on the flight deck is equipped with an oxygen/smoke mask - what the crew are checking is the flow of oxygen to the mask.

Flight crew oxygen is gaseous and there is a required bottle pressure that is checked before flight and the flow to the mask is checked. The masks are stowed in containers on the flight deck which have a test button that allows checking of the system without deploying the mask.

Most pax oxygen is chemical generators (some a/c have gaseous) and the drop out sytem and generators are checked at routine intervals by maintenance.

:)

[PAXboy]

Tiger - I can understand your point that "most usual decompression is a slow one" and gives the lie to the Hollywood delights of telling folks otherwise.

But you say, paxs don`t realise anything is wrong...they can still breathe so they just look at the mask and carry on with there in flight meal, drink or reading The Times. Whaaaat? OK, in 36 years, I have never seen them deployed but if they drop, you pull mask towards you this action opens the flow of oxygen and you place it over ... etc. ;)

Don't you? Don't they?

I am really gobsmacked by this one. I had supposed that the appearance of masks would lead to near panic!

[Departures Beckham]

I presume Tiger means this in the same way that people don't immediately head straight for an Exit when they hear a fire alarm sounding in a building. If people can't see fire or smell smoke they tend to continue until they are told otherwise by a person.

In the same way, if pax can still breathe, they don't see any need to wear the mask.