Boeing 747-400 Outflow Valve

[eloq]

Hey all, First post here.
I have an urgent question, i'm on a project for an aerospace company in Australia. We are currently building a flight simulator for ground control and i have a question.

The outflow valve has 2 buttons and 1 3-way switch.

The 2 buttons(Right and left valve) are to turn on auto mode, which will move the needle from south to north.

the switch is manual mode, which will either 1) move the needle top 2) bottom or 3) turn off manual mode.

my question is, if i move the switch up (moves needle north) and half way before it reaches completely north, i move the switch to 'off' mode, will the needle stay where it is or will it move back down.

Thank you for any help

[gas path]

On the ground BOTH indicators will indicate OPEN (point north!!).
Pushing the switchlights will put the system in manual mode. (Takes the pressurisation controller out of the loop.)
Toggle the (push on release off) toggle switch to close and the valves/indicators will move to the closed position and stop wherever they are when you release the switch. Selecting the switchlights again and the auto system will take over and drive the valves open again.
Of course if you only select one switchlight only its corresponding valve will respond to the toggle switch.

edit to correct spelling.

[TimeOnTarget]

We have a procedure for manually exercising the outflow valves during cruise flight. Certain animals produce large amounts of moisture from their breath and sweat, etc. You place one switch to manual, and then momentarily open and close the valve just a bit to make sure that it does not freeze.

I carried 2000 goats from Brisbane to Brunei once- man they stink!!!!!!!!

[eloq]

wow thats great, gas path, thanks a lot. that really cleared me up!
one more thing, when in auto mode is the toggle switch void? will it do anything if i toggle up or down when in auto mode.

and i feel bad for u TimeOnTarget haha but thanks for the example, i was wondering what they use it for.

[Dan Winterland]

On one flight, we noticed that both valves were fully open in the cruise, but the aircraft was maintaining pressure. We wrote it up in the tech log. It transpired that a loose suitcase in the number 5 bulk cargo hold had ended up being sucked over one of the valve outlets and had blocked it completely. the company fitted mesh covers over the outlets after that!

[gas path]

In auto mode the toggle switch is 'out of the loop' and will have no effect. The switch is a direct link to the d.c. motors on the valves, the automatic function being actuated by a.c motors.