73' fuel vent question

[Foxtrot]

http://www.airliners.net/photo/Continental-Airlines/Boeing-737-824/1413529

So the 737NGs also have that fuel overflow vent? I've seen the classics do that before but not the NGs.

[screaming_emu]

http://www.airliners.net/photo/Conti...37-824/1413529

So the 737NGs also have that fuel overflow vent? I've seen the classics do that before but not the NGs.

Every plane I have ever flown (which only includes one jet) has a fuel overflow vent. It actually serves two functions. If they overfuel it allows the extra fuel to be ported overboard instead of overpressurizing the fuel tank. But also as fuel is burned and depleted from the tank it allows air to go fill the place in the tank, otherwise there would be a vacuum formed and they couldn't pull any more fuel out of the tanks.

[Foxtrot]

Ahh, ok. Didn't know that, thanks for the explanation.

[Spad13]

Every plane I have ever flown (which only includes one jet) has a fuel overflow vent.

I believe they're referred to as NACA vents?

[SYDCBRWOD]

I believe they're referred to as NACA vents?

I think you'll find a NACA vent is shaped more like this (see pic). They create a low pressure zone by their tapered shape drawing air in, rather than a scoop which sits proud in the airstream (more drag). See above the wing in the Bede.

[Dmmoore]

The NACA vent provides full ram air pressure with low drag.

All NACA vents may or may not be fuel vents.

All fuel vents may or may not be NACA vents.

A NACA vent is used when a low drag vent is needed and where sufficient space is available The vent requires a lot of space. In some cases, a drag penalty is sometimes taken because a NACA vent won't fit.

[Spad13]

I think you'll find a NACA vent is shaped more like this (see pic). They create a low pressure zone by their tapered shape drawing air in, rather than a scoop which sits proud in the airstream (more drag). See above the wing in the Bede.

And that's exactly what that vent is shaped like on the airplane I (and screaming emu) fly. I'm pretty sure the one on the B737 is similar.

[SYDCBRWOD]

And that's exactly what that vent is shaped like on the airplane I (and screaming emu) fly. I'm pretty sure the one on the B737 is similar.

If its a fuel overflow why not a simple pipe to discharge the excess? Why the need to pressurise a part of the wing?

[Dmmoore]

If its a fuel overflow why not a simple pipe to discharge the excess? Why the need to pressurise a part of the wing?

Under stand the tanks "must" be vented to allow the tanks to fill and empty normally. The vent on each wing are used as overflows. There is no need for a separate overflow.

[HAWK21M]

To Avoid cavitation due vapour lock.vents are needed.A blocked vent can be relieved by a Access panel pressure relief valve present inboard of the vent.
regds
MEL