rjm777ual
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How Does Dirt Form On Aircraft?

Tue Jun 19, 2012 3:13 am

How exactly does dirt form on aircraft? My first thought was pollution, but that didn't seem right. Any ideas?
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brilondon
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RE: How Does Dirt Form On Aircraft?

Tue Jun 19, 2012 3:21 am

Dust, air pollution, grime from what ever is on the ground. How does dirt get under my fingernails when I don't leave my office all day?
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September11
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RE: How Does Dirt Form On Aircraft?

Tue Jun 19, 2012 3:58 am

Shoes? Dirt from underneath shoes are brought into planes.
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fr8mech
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RE: How Does Dirt Form On Aircraft?

Tue Jun 19, 2012 8:12 pm

How does dirt get on cars. Same mechanism. Don't discount pollution.
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ALTF4
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RE: How Does Dirt Form On Aircraft?

Tue Jun 19, 2012 8:20 pm

I throw mud at Air France planes. Apparently I'm fairly effective - people on here complain about AF planes being so dirty!

In all seriousness, think about the smoke/exhaust you see trailing out of an engine on climb-out, especially if you're looking at a plane from the ground. Certainly enough of that is left in the air, at least on the runway, for the plane taking off behind to catch some of it.
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soon7x7
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RE: How Does Dirt Form On Aircraft?

Thu Jun 21, 2012 12:22 am

Quoting ALTF4 (Reply 4):
I throw mud at Air France planes


Excellent!...Thrust reversing creates soot around the wing roots and whole area...Overtime, rivets and fasteners loosen and galling creates small dirty trails of dark grey aluminum. Think its called "fretting". Corrosion on bare metal and topcoat paint oxidation all add the make the airframe look like crap. Oxidized paint holds dirt , bird poo and all other stains forever.
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Starlionblue
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RE: How Does Dirt Form On Aircraft?

Thu Jun 21, 2012 6:24 am

Quoting soon7x7 (Reply 5):
Don't ever under estimate pigeon craps strength!. On a flight from NY to Germany, a New York pigeon pooed on the wing. That poo last the entire flight into Europe the next a.m.!

Yeah that stuff is sticky! Also perhaps it was in a slight flow depression area. 
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Francoflier
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RE: How Does Dirt Form On Aircraft?

Thu Jun 21, 2012 7:15 am

Quoting ALTF4 (Reply 4):
I throw mud at Air France planes. Apparently I'm fairly effective - people on here complain about AF planes being so dirty!

B*tch, please.
Don't flatter yourself.
If anything, the water content of the mud cleans the crap that's underneath.
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Horstroad
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RE: How Does Dirt Form On Aircraft?

Thu Jun 21, 2012 1:05 pm

grease, rubber, carbon dust, hydraulic fluid, oil, coffee, dust and dirt from the ground/atmosphere
 
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HAWK21M
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RE: How Does Dirt Form On Aircraft?

Sat Jun 23, 2012 6:49 pm

Dust in the Atmosphere... adherence increases if there is an oil/fluid leak.
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Northwest727
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RE: How Does Dirt Form On Aircraft?

Sun Jun 24, 2012 12:23 pm

Another thing is soot and oil blowing out of the exhaust of turbine engines. Ever notice on Pratt and Whitney Canada PT6A powered airplanes, there is a trail of soot and oil behind the exhaust stacks? I've seen what those engines do to a freshly polished/waxed Piper Meridian after just an hour's flight, so after several hours, you can imagine what the airplane looks like.

You can also see the stains on 727s, old 737-100/200s on the fuselage, DC-9s, Tupolev 154s, etc right around the vicinity on the thrust reversers.
 
Tod
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RE: How Does Dirt Form On Aircraft?

Sun Jun 24, 2012 12:40 pm

The stuff coming out of the drain masts can add pretty streaks too.
 
L-188
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RE: How Does Dirt Form On Aircraft?

Sun Jun 24, 2012 11:57 pm

My last airline had a white Metro III that at one point had been flown by Horizon Air.

Every summer it would get all these little red splats all over the nose from all the bugs and Mosquitos that it would hit inflight (this being Alaska, many blood sucking Mosquitos). Anyway that earned it a nickname amount the mechanics.

Since this is a family forum I will not repeat the nickname here, but it was called a feminine hygiene product,
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L-188
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RE: How Does Dirt Form On Aircraft?

Mon Jun 25, 2012 6:53 am

Another source of filth on aircraft you don't see nearly as much these days but get some photos of DC-10's taken back in the 1970's through the middle 1980's and you will often, especially on white painted aircraft see a long brown streak starting from the cabin outflow valve.

That is a nicotine stain. Basic back when you still had smoking on aircraft when the planes would land, the outflow valve would open and all the smoke filled air from inside the aircraft would exit through that valve and cause that stain down side of the airplane.

There used to be a really good photo of a Western DC-10 on this site with that streak in full evidence, but I haven't able to locate it.
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737tdi
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RE: How Does Dirt Form On Aircraft?

Mon Jun 25, 2012 7:41 am

Quoting L-188 (Reply 13):
the outflow valve would open and all the smoke filled air from inside the aircraft would exit through that valve and cause that stain down side of the airplane.





Even with the outflow valve closed there is a tremendous amount of air leaving the aircraft, through the outflow valve, the galley and lav. vents etc. This is what caused the streaks, not when the outflow valve opened on landing, it partially opens and closes thousands of times during the flight. The amount of airflow into the cabin is pretty much constant, cabin pressure is maintained/controlled through the outflow valve modulating.

Keep in mind also that there are fluid leakage limits, whether it be 1 drop per minute etc.. It will create an environment for dirt to stick too.

Then you have air pollution as mentioned earlier. Walk outside at night and shine a flashlight vertically in front of your eyes. You will see tons of debris in the air, most being plant origin but it still makes an aircraft very dirty.
 
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HAWK21M
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RE: How Does Dirt Form On Aircraft?

Mon Jun 25, 2012 10:13 am

Thats why routine washing followed by a polish does help visually and aerodynamically.
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Northwest727
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RE: How Does Dirt Form On Aircraft?

Mon Jun 25, 2012 3:46 pm

Quoting L-188 (Reply 13):
That is a nicotine stain.

Very true; I think one of the "clues" investigators found behind the cause of JAL123 was nicotine stains around the failed doubler plate on the rear pressure bulkhead...stains left by cigarette smoke-laden air escaping passing by the failing seal.
 
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HAWK21M
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RE: How Does Dirt Form On Aircraft?

Tue Jun 26, 2012 9:06 am

In those days of Nicotine fumes.....The clogging of the relief valve filters was a problem that occured a lot.
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737tdi
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RE: How Does Dirt Form On Aircraft?

Wed Jun 27, 2012 12:01 am

Hawk21: I see you remember those days, remember changing the outflow valves then? Wow they were a sticky mess plus anything behind the aft bulkhead in the aft. bag bin was coated in gunk.
 
comorin
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RE: How Does Dirt Form On Aircraft?

Wed Jun 27, 2012 10:31 am

Would flying a plane through rain at 500 mph wash off all the dirt? Or does boundary layer effect get in the way?
 
tdscanuck
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RE: How Does Dirt Form On Aircraft?

Wed Jun 27, 2012 11:09 am

Quoting comorin (Reply 19):
Would flying a plane through rain at 500 mph wash off all the dirt? Or does boundary layer effect get in the way?

That will help only at the leading edges; boundary layer kills most of that off for most of the rest of the plane, especially towards the backs of things.

Tom.
 
comorin
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RE: How Does Dirt Form On Aircraft?

Wed Jun 27, 2012 3:46 pm

Quoting tdscanuck (Reply 20):
Quoting comorin (Reply 19):
Would flying a plane through rain at 500 mph wash off all the dirt? Or does boundary layer effect get in the way?

That will help only at the leading edges; boundary layer kills most of that off for most of the rest of the plane, especially towards t

Thank you for confirming that; somewhat like what happens when a car is driven through the rain.
 
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817Dreamliiner
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RE: How Does Dirt Form On Aircraft?

Thu Jun 28, 2012 2:04 am

Quoting comorin (Reply 19):

Would flying a plane through rain at 500 mph wash off all the dirt? Or does boundary layer effect get in the way?

Not really. What you need to remember is that an aircraft fuselage is not a perfectly smooth surface and there will be areas where dirt will form regardless of the air friction as its flying.
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rfields5421
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RE: How Does Dirt Form On Aircraft?

Thu Jun 28, 2012 4:14 am

Quoting rjm777ual (Thread starter):
How exactly does dirt form on aircraft? My first thought was pollution, but that didn't seem right. Any ideas?

Have you seen images of the amount of dirt thrown into the air by wind storms in the southwest US. PHX has been closed at times because the dirt in the air is too thick. We have dirt fall on our cars and outdoor furniture here near Dallas from those storms. And on the aircraft at local airports.

There are dozens of volcanos around the world throwing several tons of dirt into the air each month. It goes all around the world.

Right now we are seeing some particulate falling from the wild fires in Colorado and New Mexico.

Pollution is a contributor of course - but the air is filled with dirt from many natural sources.

One reason things seem so fresh after a rain is that the first thing rain does is wash the dirt out of the air.
 
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HAWK21M
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RE: How Does Dirt Form On Aircraft?

Thu Jun 28, 2012 4:09 pm

Quoting 737tdi (Reply 18):
Hawk21: I see you remember those days, remember changing the outflow valves then? Wow they were a sticky mess plus anything behind the aft bulkhead in the aft. bag bin was coated in gunk.

True....thats when todays aviation Maintenance is much cleaner & more electronic  
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