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What are these triangles and ribbons on this MD83's wing, and what do they do?

View from cabin of wing with ribbons and triangles pointed out

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These are Ice Detection Tufts that check for ice. If they are stuck, it indicates there's a layer of ice on the wing, disturbing airflow and presenting a danger for the engines when it detaches. They are focused around the rear root side since this is most likely to be the spot with the most buildup, as remaining cold fuel below flows to this corner.

SAS had an incident with ice a few years ago in the Gottröra Accident (SAS Flight 751) that thankfully ended relatively well.

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    $\begingroup$ Are they purely visual in nature? Or are they connected to some kind of sensor? $\endgroup$ – Bassinator Nov 15 '14 at 18:03
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    $\begingroup$ Purely visual; I have never heard of digital wing ice sensors in use on commercial aircraft. $\endgroup$ – Thunderstrike Nov 15 '14 at 22:09
  • $\begingroup$ Why wouldn't ice build up on the leading edge first? Certainly the fuel can't be any colder than the OAT? $\endgroup$ – Rhino Driver Nov 15 '14 at 22:51
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    $\begingroup$ @HCBPshenanigans Ground staff and/or pilots check that they are free before flight either by method of deicing fluid, weather or trying to move them. $\endgroup$ – Thunderstrike Nov 15 '14 at 23:48
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    $\begingroup$ @MikeFoxtrot Ah, so its mainly a ground check function, that makes sense to me now. Thanks. $\endgroup$ – Rhino Driver Nov 16 '14 at 0:22
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Some more information about this particular item.

AD 2002-21-06 addresses the issues with detecting wing ice on the DC-9 series of aircraft (which includes the MD-83).

Some aircraft of this type have a wing surface ice detection system installed.

Wing Ice Detection system diagram

There is also a modification available that automatically moves fuel between the wing and center fuel tanks to prevent the supercooled fuel from accumulating in wing tanks.

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