B738 Smoke or Fumes Removal NNC

[asteroid01]

This question relates specifically to the 738, other models have very different layouts including FWD Outflow valves which the NG lacks. They also have different QRH's and different MEL's.

Using the Smoke or Fumes Removal NNC, when both Pack switches are off and the smoke or fumes source is confirmed be outside the flight deck, what forces the smoke out via the outflow valve?
Suction will only create a vacuum.

This also relates to the PACK NNC and why speed has to be kept above 290kt? Surely speed can only keep cockpit/cabin heat down if there is some kind of forced ventilation system that bypasses the packs.

The Dash 8 had a NACA duct on the dorsal fin to provide Emergency Ram Air Ventilation to provide, albeit a very low, flow rate when both pack were off/failed. This slight positive flow would then displace smoke via the outflow valve. Does the 738 have something similar that we have not been told about?

This topic was discussed, without satisfactory conclusion, in April 2004 under the topic "B737 NG Pack Trip Off".

[asteroid01]

To re phrase the question, if both packs fail, the PACK reference checklist requires "Maintain 290 knots minimum. Flight deck and cabin temperatures may increase rapidly at speeds below 290 knots".

Errrr, can anyone explain how speeding up will keep temperatures down? Surely speed will exacerbate the problem via TAT?

[BOAC]

I would guess the small increase in TAT would be insignificant compared to the benefit of a through-flow of cold air to remove 'electrical' heat.

[ahramin]

TAT will have a negligible effect on cabin temperature.