Recent UA peeling paint livery sightings

Old Sep 13, 19, 5:04 pm
  #31  
 
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Not particularly paint related but noticed this on the wing of a recent flight. Having been a auto mechanic in a prior life, I know dirt is usually attracted to oil/fluid which was somewhat disconcerning. The dirt patched didnt grow throughout the flight, and I assumed any leak would have set off a low/abnormal pressure indicator so maybe it was leftover from a prior leak?
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Old Sep 13, 19, 7:19 pm
  #32  
 
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Originally Posted by scracer14 View Post
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Not particularly paint related but noticed this on the wing of a recent flight. Having been a auto mechanic in a prior life, I know dirt is usually attracted to oil/fluid which was somewhat disconcerning. The dirt patched didnt grow throughout the flight, and I assumed any leak would have set off a low/abnormal pressure indicator so maybe it was leftover from a prior leak?
To my inexpert eye, the smudges appear to start at the leading edge, which would imply the cause is (was?) external to the wing. It slightly difficult to interpret, but the accumulation further back is likely resulting from vortices generated at the panel seam.

edit: good answer below.

Last edited by fumje; Sep 13, 19 at 7:25 pm
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Old Sep 13, 19, 7:23 pm
  #33  
 
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The black marks come from metal rubbing against metal in a moist environment, i.e. clouds or rain. They are extended back from the area of each set of slat tracks.

This is one way that mechanics identify rivets that are a bit loose. The slight movement that they allow produces those black streaks.
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