alaskan9974
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737 Aileron Water Buildup?

Thu Jul 11, 2013 8:43 pm

Was on a flight this morning from KSEA on Seattle Airlines. Never seen so much fluid coming from the wing before. I usually sit in F but booked late and ended up in the exit row so not sure if this is a normal occurrence.

The fluid began streaking across the top of the aileron after takeoff began just before rotation, was a lot of fluid, enough to leave a vapor trail from takeoff until cruising alt. I wasn't able to get a good picture of the vapor trail, it was hard to get it to contrast against clouds. At one point it was flowing across the entire aileron. The last time I can remember seeing fluid coming from their aircraft was on their 732's which is common on those engines, this was definitely in a much higher quantity. We were delayed for mech. for about 20 minutes before takeoff but apparently everything checked out.

I asked a FA in passing and she mentioned it was probably water. Just before descent, looked out and the fluid was still coming out 3 hours later, still leaving a vapor trail. Buddy of mine was in 17a so I took a look out that window and no vapor on the LH side. Hard for me to imagine enough water building up to still be flowing 3 hours later, at least in quantities enough to leave a vapor trail. After deplaning I saw a small puddle underneath the outside of the wing.
 
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kc135topboom
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RE: 737 Aileron Water Buildup?

Thu Jul 11, 2013 9:01 pm

Probably not water. After 3 hours at high altitude, the water would have frozen. Most likely it is a very minor fuel leak that had not been detected at SEA. I doubt it is hydraulic fluid.

I know that it rains a lot in SEA, and the B-737 has dry bays in the wings, but at most they only hold a gallon or so of rain water, which would have been al gone within a few minutes of T/O.

Who is "Seattle Airlines"?
 
roseflyer
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RE: 737 Aileron Water Buildup?

Thu Jul 11, 2013 9:09 pm

That is in the vicinity of the fuel surge tank. There is a pressure relief valve that opens in climb and descent to regulate air pressure in the tanks. The Surge Tanks only hold about 200lbs of fuel. Typically in level flight, fuel will flow back from the surge tank into the wing tank, but I guess it is possible that there is something clogging that line, and fuel could be venting out the surge tank in flight. It’s not a huge problem, because it isn’t a fuel leak and the system is designed to vent fuel when needed, but if it was fuel, someone should notice it dripping under the wing at the gate.
If you have never designed an airplane part before, let the real designers do the work!
 
alaskan9974
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RE: 737 Aileron Water Buildup?

Thu Jul 11, 2013 9:12 pm

Quoting KC135TopBoom (Reply 1):

ASA

I figured it wasn't water and I was thinking along the lines of hydraulic fluid, I know there is a manual revision as well as a secondary hydraulic system, the FA didn't seemed bothered in the least when she saw it so I didn't think too much of it.
 
roseflyer
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RE: 737 Aileron Water Buildup?

Thu Jul 11, 2013 9:20 pm

Quoting alaskan9974 (Reply 3):
I figured it wasn't water and I was thinking along the lines of hydraulic fluid, I know there is a manual revision as well as a secondary hydraulic system, the FA didn't seemed bothered in the least when she saw it so I didn't think too much of it.

Flight Attendants are trained never to look bothered, so that you won’t be worried. That doesn’t mean that she didn’t make a comment to the captain about it. It’s awfully boring in cruise and the pilots usually don’t mind a distraction from a flight attendant even though many passenger complaints about something wrong with the airplane are nothing. On occasion passengers do notice things that do need to be reported and fixed.

9 times out of 10 on Alaska if someone asks a flight attendant what landmark they just flew over, the FA will usually call to the flight deck and come back and tell you what you just passed. It’s really up to the crew. Some flight attendants are notorious about what they’ll say to passengers and make up complete lies to get them to be quiet, but that is not your typical crew.
If you have never designed an airplane part before, let the real designers do the work!
 
N14AZ
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RE: 737 Aileron Water Buildup?

Thu Jul 11, 2013 9:25 pm

Seattle Airlines? Did I miss anything? Never reard about such an airline.
 
L0VE2FLY
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RE: 737 Aileron Water Buildup?

Thu Jul 11, 2013 9:32 pm

Quoting N14AZ (Reply 5):
Seattle Airlines? Did I miss anything? Never reard about such an airline.

Oh yeah, there's such an airline, it's based in Alaska!  
 
alaskan9974
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RE: 737 Aileron Water Buildup?

Thu Jul 11, 2013 9:32 pm

Quoting N14AZ (Reply 5):

Just a nickname for ASA, sometimes hear it in the P. northwest.
 
Tristarsteve
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RE: 737 Aileron Water Buildup?

Thu Jul 11, 2013 9:54 pm

Quoting alaskan9974 (Reply 3):

I figured it wasn't water and I was thinking along the lines of hydraulic fluid

Water would have frozen.
The aileron actuators are in the wheel bay, there is no hydraulics that far out.

Quoting roseflyer (Reply 2):
That is in the vicinity of the fuel surge tank

Yes and the air inlet is under the wing about where your leak is.
But the surge tank should be empty of fuel at all times in flight. I suspect a valve is not closing, allowing fuel into the surge tank, where you can see it leaking.

Quoting roseflyer (Reply 2):
It’s not a huge problem, because it isn’t a fuel leak

But it is a fuel leak. How much fuel would you like to leak out of the tanks in flight?

Quoting alaskan9974 (Reply 7):
Just a nickname for ASA,

Is that Alaska Seattle Airlines? the same as Alaska Airlines?
 
aklrno
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RE: 737 Aileron Water Buildup?

Thu Jul 11, 2013 10:07 pm

Quoting roseflyer (Reply 4):
Flight Attendants are trained never to look bothered, so that you won’t be worried. That doesn’t mean that she didn’t make a comment to the captain about it. It’s awfully boring in cruise and the pilots usually don’t mind a distraction from a flight attendant even though many passenger complaints about something wrong with the airplane are nothing. On occasion passengers do notice things that do need to be reported and fixed.

Several years ago I noticed a screw on an some panel (perhaps an inspection port, don't remember the A/C type) that was completely out of its hole and held by some capture mechanism. I pointed it out to the FA who said she would inform the pilots. A couple of minutes later the F/O casually wandered back to my row and looked out the window. He said it looked harmless but would probably add $5 to the fuel bill in excess drag. All appeared very casual, but the response was fairly prompt.
 
roseflyer
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RE: 737 Aileron Water Buildup?

Thu Jul 11, 2013 11:12 pm

Quoting Tristarsteve (Reply 8):
Quoting alaskan9974 (Reply 3):

I figured it wasn't water and I was thinking along the lines of hydraulic fluid

Water would have frozen.
The aileron actuators are in the wheel bay, there is no hydraulics that far out.

The furthest outboard slat actuator is located in front of the aileron if I remember correctly (that looks like a 737-400 wing and I’m not that familiar with the older 737s), but I agree that the leak path for a slat actuator would not be on the aileron like that.

Quoting Tristarsteve (Reply 8):
Yes and the air inlet is under the wing about where your leak is.
But the surge tank should be empty of fuel at all times in flight. I suspect a valve is not closing, allowing fuel into the surge tank, where you can see it leaking.

Yes the tank should be empty. I was wondering if there was an obstruction that wasn’t allowing fuel that flowed into the surge tank from flowing back into the wing tanks when the plane is in level flight. But you may be exactly right too. I think we both agree that it looks like something is wrong, but it is hard to know what would cause it.

Quoting Tristarsteve (Reply 8):
Quoting roseflyer (Reply 2):
It’s not a huge problem, because it isn’t a fuel leak

But it is a fuel leak. How much fuel would you like to leak out of the tanks in flight?

I guess it is kind of a fuel leak. It’s not a leak in the sense of the tank being penetrated or broken fuel line. It’s a leak coming from a drain where air or excess fuel/air mixture is supposed to vent from. But I agree it should not be venting anything but air in flight I you can call it a fuel leak. It isn’t the type of fuel leak that will appreciably affect the useable fuel quantity.
If you have never designed an airplane part before, let the real designers do the work!
 
yeelep
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RE: 737 Aileron Water Buildup?

Fri Jul 12, 2013 4:38 pm

Quoting L0VE2FLY (Reply 6):
Oh yeah, there's such an airline, it's based in Alaska!  

They haven't been based in Alaska for over 60 years.

Quoting Tristarsteve (Reply 8):
Is that Alaska Seattle Airlines? the same as Alaska Airlines?

Yes, Alaska Airlines. ASA is the ICAO code, AS is the IATA code.

Quoting Tristarsteve (Reply 8):
Yes and the air inlet is under the wing about where your leak is.

The vent is a little to far outboard to be the source of the discoloration/streaks on the aileron. Much more likely that one of the fuel tank access panels is leaking. Could also be a leading edge hydraulic leak.
 
AA737-823
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RE: 737 Aileron Water Buildup?

Tue Jul 16, 2013 9:29 pm

Quoting yeelep (Reply 11):
Yes, Alaska Airlines. ASA is the ICAO code, AS is the IATA code.

I think he was asking what ASA stands for- it's Alaska Star Airlines, certainly NOT Alaska Seattle Airlines.... lol!

Quoting yeelep (Reply 11):
Much more likely that one of the fuel tank access panels is leaking.

Indeed, those babies DO leak.
 
alaskan9974
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RE: 737 Aileron Water Buildup?

Tue Jul 30, 2013 10:44 pm

I was looking back through my saved pictures earlier, I didn't realize my camera was able to see the vapor. Anyways, it does not look like much was coming out, at least looking back at the photo.

 
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CALTECH
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RE: 737 Aileron Water Buildup?

Wed Jul 31, 2013 3:50 am

Well, the vapor trail seems to be in line with the air vent scoop for a Classic. Drawings show this.

On the NG, I agree, the vent would be further out past the aileron. The AMM drawings show this also.

But this is a 737 classic.

[Edited 2013-07-30 21:16:32]
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MD11Engineer
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RE: 737 Aileron Water Buildup?

Thu Aug 01, 2013 9:07 am

Quoting roseflyer (Reply 2):
That is in the vicinity of the fuel surge tank. There is a pressure relief valve that opens in climb and descent to regulate air pressure in the tanks. The Surge Tanks only hold about 200lbs of fuel. Typically in level flight, fuel will flow back from the surge tank into the wing tank, but I guess it is possible that there is something clogging that line, and fuel could be venting out the surge tank in flight. It’s not a huge problem, because it isn’t a fuel leak and the system is designed to vent fuel when needed, but if it was fuel, someone should notice it dripping under the wing at the gate.

Actually the surge tanks (into which the fuel tank venting system leads) are permanently ventilated by a NACA vent with a flame arrestor on the lower side of the wing. Should this opening be clogged up, there exists a positive / negative pressure relief valve beside it, which will pop out if activated and will stay pooped out until reset by maintenance on the ground.
If fuel enters the fuel tank venting system, it will end up in the surge tanks. The rib between the wing tank and the adjoining surge tank has a bunch of flapper valves installed, which will let this fuel run back into the wing tank.

Sometimes, if the overfill protection (which is actuated by a float switch in each surge tank) doesn´t work (it shuts down refuelling immediately) and the fueler doesn´t pay attention and overfills the tanks, so that fuel goes through the vent system into the surge tanks, there will be fuel coming out from the NACA inlet.

Jan
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redflyer
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RE: 737 Aileron Water Buildup?

Thu Aug 08, 2013 6:16 pm

Quoting Tristarsteve (Reply 8):
I suspect a valve is not closing, allowing fuel into the surge tank, where you can see it leaking.
Quoting MD11Engineer (Reply 15):
Sometimes, if the overfill protection (which is actuated by a float switch in each surge tank) doesn´t work (it shuts down refuelling immediately) and the fueler doesn´t pay attention and overfills the tanks, so that fuel goes through the vent system into the surge tanks, there will be fuel coming out from the NACA inlet.

I noticed a similar event occur a few years back when I flew on a WN 733, except it was out of the left wing in the outboard flap area near the aileron. If memory serves me correctly, I actually saw the liquid leaking out during taxi and I thought it was water draining out of gaps in the wing. However, once we took off there was a distinct vapor trail forming over the flap and then once the flaps were retracted the vapor trail was coming from beneath the flap. I was going to say something to the flight attendant once we got up to cruise if it didn't stop, but it in fact did stop shortly before reaching cruise altitude. Given that this was in a slightly different area, was it a different cause/event?
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