x-refer as no response.

[Natstrackalpha]

http://www.pprune.org/questions/4788...s-ram-air.html

[737Jock]

You're looking for this I think.

An emergency ram air inlet ventilates the cockpit and cabin to remove smoke, or if both packs fail. The emergency ram air inlet valve is controlled by the RAM AIR pushbutton on the AIR COND panel. This pushbutton opens the ram air valve, provided that ditching is not selected.

When the RAM AIR pushbutton is ON : The outflow valve opens about 50 %, provided that it is under automatic control and ▵P is less than 1 PSI. The outflow valve does not automatically open if it is under manual control, even if ▵P is less than 1 PSI. If ▵P is greater than 1 PSI, the check valve located downstream the ram air door will not open, even if the ram air door has been selected open. No airflow will then be supplied.

So Ram air can only be used when ▵P < 1 psi otherwise it simply won't supply air. It can be closed again with the pushbutton.

Your questions:

1/. If in normal conditions with pressurisation normal no faults and the Ram Air is opened, will this de-pressurize the aircraft.

No, needs to have ▵P < 1 ps

2/. If using the Ram Air vent for whatever reason, (smoke clearence say) and situation is rectified, i.e., smoke all gone, source diminished (for example) then can Ram Air be closed again in flight?

Yes, Ram air can be closed inflight. But smoke clearance is not a good example.

3/. If decompression, can / will Ram Air save the day or have any effect at all - if so does this mean that Ram Air would provide adequate Cabin Alt (pressurisation) . . ?

No, Ram air does not pressurize the cabin. Although you could argue that if there is more air going in (through ram air) than going out (outflow valve closed) it would provide some pressurization.

[Natstrackalpha]

Thanks Jock. merely out of general curiosity - sorry to be a pain . . why wasn`t the smoke clearence a good example - I cannot think of any othe reason for venting the cabin . .. ?

Thanks once again.