Fuel leak? AA738 (Photos attached)

[brianw999]

I recall an occasion when the passengers on a Phuket Airlines 747 flatly refused to all ow a takeoff when fuel was seen pouring from a wing vent.

...with that airlines track record on maintenance before they went bust it's probably the best decision those passengers ever made in their life.

[fabster4444]

Related!

http://aviacioncr.net/foto.php?id=47459

f.

[m.swofford]

Fuel Venting

Airliners generally have one fuel vent near the outboard end of each wing. Passenger 747-400s also have a 22,000 lb fuel tank in the horizontal stabilizer and its vent is located on the outboard starboard horizontal stabilizer. The fuel vent system is usually connected to a surge tank nearby which takes up excess fuel due to expansion and returns the fuel to the associated tank as the fuel drops due to consumption.

On rotation or shortly after takeoff as in the case of these photos, some fuel still in the surge tank is being vented throught the fuel vent. These vents are on the bottom of the wind and use a NACA duct that is usually pressure neutral, neither pressurizing or suctioning fuel from the surge tank and their shape avoids contamination and blockage from ice or rain.

Vapor trails also seen during takeoff and especially landing usually form in high humidity conditions in vorticies from the outboard trailing edge flaps and not the wing tips. The low pressure in the center of these cause water vapor to temporarily form droplets due to the drop in temperature and pressure.

Continuous vapor trails normally only form in very cold or humid conditions during high angle of attack flight such as fighter maneuvres or during takeoff and landing. Continous fuel vapor trails would be evidence of fuel leakage and cause for concern. But it would be difficult or impossible to tell the difference from the ground.

Older jet, turbine and reciprocating engines vent oil and unburnt fuel as a dense smoke trail from the engine itself.

[B7772ADL]

Here's another couple of occassions where this has occurred -

[photoid=305179]

I remember that one very well....the chief fire officer wasn't a happy chappy at all that Snowbird was venting fuel all over the place. The aircraft elected to continue on it's journey and safely got away, if a little alarming to see.

[RingwaySam]

I saw a 747-300 with fuel coming out a few months ago. The airport had to shift the mess which was on the runway. They carried on there journey though.

[meneses24]

I got a simmilar picture one of this days

[photoid=5873774]

[Foxtrot]

Re:

Wow, interesting info. I never knew either that airplanes have fuel tank vents, but it makes sense now that I know. This also explains what I saw from an AI 742 back in '91. Right after takeoff, I saw a small stream of white coming out of the wing, from underneath it, between the engines (I was right behind the trailing edge). I was a little alarmed at first, but after a while it stopped and we continued w/o any problems. You may say it was vapour streaming from the flaps or flap guide, but this was the only white stuff streaming back and there was nothing else streaming from the wing. Also, it was continously streaming, not like vapour which is random in behaviour.

[JJR]

I'll chirp in since I used to be a fueler . That is in fact the #2 Main Tank fuel Vent. The wind going over it creates a suction, and/or the overfill tank is draining some. Nothing major.

Probably nothing to do with trying to squeeze in that last 15 gallons when it VTO's @ 8.5 on a wicked hot day?????? Maybe he forgot to let go of the button.....

[Admin Airbus]

thats a slipstream i think

is that not a slipstream. if the pressure on the plane below the wing is higher than the upper part of the wing then the slip stream comes from the bottom... I THINK ONLY

[AJ]

From the 737 notes at http://www.smartcockpit.com/

4. FUEL VENT SYSTEM
¡ The purpose of the fuel vent system is to prevent damage to the wings due to excessive buildup
positive or negative pressure inside the fuel tanks and to provide ram air pressure within the
The tanks are vented into surge tanks which vent through a single opening at each wing tip.

[ExpressJet145]

This is very interesting, as screaming_emu I have seen fuel coming out of the vents of smaller aircrafts such as PA-28s and C177s.

How many fuel vents does a 737 has and where are they located?

On the 737s, there is one fuel vent for each tank, located near the wing tips on each wing (like in the pic). As far as the center fuel tank, Im really not sure to be honest with you. I dont think the center tank vents through the wings, it has its own vent, but Im not sure where it is. With MD80s you cant fill the wing tanks to max capacity of 9300lbs until the center tank is properly loaded accordingly to the fuel load. Hope this helps!

[[email protected]]

I'll chirp in since I used to be a fueler . That is in fact the #2 Main Tank fuel Vent. The wind going over it creates a suction, and/or the overfill tank is draining some. Nothing major.

This is very interesting, as screaming_emu I have seen fuel coming out of the vents of smaller aircrafts such as PA-28s and C177s.

How many fuel vents does a 737 has and where are they located?

[screaming_emu]

I'll chirp in since I used to be a fueler . That is in fact the #2 Main Tank fuel Vent. The wind going over it creates a suction, and/or the overfill tank is draining some. Nothing major.

I've actually had fuel come out of my fuel vent in flight. Was getting bounced around pretty hard in a Cirrus SR-20 and every once and a while we'd see some fuel come out below the trailing edge.

[ExpressJet145]

I'll chirp in since I used to be a fueler . That is in fact the #2 Main Tank fuel Vent. The wind going over it creates a suction, and/or the overfill tank is draining some. Nothing major.

[screaming_emu]

I wasn't aware that airliners had some sort of relief valves, besides the ones used for fuel dumping.

yup, all aircraft need fuel vents to allow air to fill the fuel tanks when the fuel is drawn out. If they dont, a vacuum would be formed and they would no longer be able to get any more fuel. Its also there for when the fuel expands due to changing temperatures to allow it to leak out, instead of making the pressure inside the fuel tank get too high.