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MD-80 Series -- Strings Tied To Wing?  
User currently offlineBrenintw From Taiwan, joined Jul 2006, 1634 posts, RR: 1
Posted (5 years 1 month 1 week 9 hours ago) and read 7037 times:

Recently I flew JNB - DUR on a 1Time MD-80 series aircraft. I was seated over the wing and had a window seat.

While looking down I noticed three yellow triangles painted on the wing. At the center of the triangle was a "pin" with a red string tied to it.

They'd obviously been there a while, since I could see polished arcs around where the strings would end.

What would these be for?


I'm tired of the A vs. B sniping. Neither make planes that shed wings randomly!
19 replies: All unread, jump to last
 
User currently offlineZBBYLW From Canada, joined Nov 2006, 1984 posts, RR: 6
Reply 1, posted (5 years 1 month 1 week 9 hours ago) and read 7040 times:

These would be static wick's which help "wick" static electricity out of the aircraft. The polished arcs at the end are purpose built to help the electricity desipate.


Keep the shinny side up!
User currently offlineBrenintw From Taiwan, joined Jul 2006, 1634 posts, RR: 1
Reply 2, posted (5 years 1 month 1 week 9 hours ago) and read 7030 times:



Quoting ZBBYLW (Reply 1):

Static wicks are normally quite far outboard -- aren't they? These were right close to the window.

Additionally, from the pictures I've seen here, static wicks are normally metallic. The red strings I was talking about looked like standard nylon (or similar) string.

FWIW, my return flight was on another MD-80 series, and it lacked the strings.



I'm tired of the A vs. B sniping. Neither make planes that shed wings randomly!
User currently offlineMax Q From United States of America, joined May 2001, 4470 posts, RR: 19
Reply 3, posted (5 years 1 month 1 week 8 hours ago) and read 7029 times:



Quoting ZBBYLW (Reply 1):



These would be static wick's which help "wick" static electricity out of the aircraft. The polished arcs at the end are purpose built to help the electricity desipate.

I have to disagree, you will find static wicks at the trailing edge of the wings, vertical and horizontal stabilisers.


The yellow triangles with the attached strings are part of an 'ice detection system'


The MD 80 has always had a problem with ice forming above the wing because of the cold soaked fuel contained within.


This could be undetected during a turn around where there is inadequate time for the ice to melt and on the subsequent take off, break off and be ingested by the rear mounted engines.


This happened several times including one SAS incident that induced a complete power loss immediately after take off. The Pilots made a brilliant dead stick landing with no fatalities.


The 'strings' on the yellow triangles allow an inspecting Pilot or Mechanic to check, by using a long 'wand' to see if they moved freely on the ground. If they did not there was probably ice sticking to the top of the wing preventing their movement.


In four years as a FO on the MD80 I did this check many, many times !



The best contribution to safety is a competent Pilot.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17030 posts, RR: 67
Reply 4, posted (5 years 1 month 1 week 8 hours ago) and read 7012 times:



Quoting Max Q (Reply 3):
The MD 80 has always had a problem with ice forming above the wing because of the cold soaked fuel contained within.

Would it be more accurate to say that ice on the MD-80 is more of a problem than on other aircraft given the fact that ice can fall off the wing and get into the engines?



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline113312 From United States of America, joined Apr 2005, 571 posts, RR: 1
Reply 5, posted (5 years 1 month 6 days 18 hours ago) and read 6825 times:

As previously stated, there were a number of engine failures, and accidents, that were attributed to chunks of ice being ingested into the engines. It was found that super cooled fuel, remaining in the wing tanks, would cause ice to form on the upper surface of the wing close to the fuselage while the aircraft was parked on the ground between flights. Due to the ambient temperature, ice wouldn't otherwise be expected anywhere on the plane. But it would form at this location due to the cold fuel and cold surface of the upper wing skin in contact with moist air. This ice, if undetected and removed, could break free during takeoff and chunks fly into the engine.

All MD80 operators had to implement procedures to determine that this area was ice free. Some airlines painted black areas to aid is visual inspection and others painted it yellow and added the string. Most require a pilot, or other trained person, to make the visual inspection prior to every departure. Some place a ladder at the leading edge to facilitate this and others take a look out through the cabin window.

Since this form of ice build up has nothing to do with in-flight icing, the anti-ice and deice systems of the aircraft will not prevent or remove the ice. I am sure that someone can confirm that some airlines have installed an aftermarket laminated electric pad to aid in removing this ice. Others have to obtain deicing on the ground from the usual source.


User currently offlineAirframeAS From United States of America, joined Feb 2004, 14150 posts, RR: 24
Reply 6, posted (5 years 1 month 6 days 17 hours ago) and read 6824 times:

Do we have a picture of this part in question on the M80 wing so I can get a better idea of what is being talked about?


A Safe Flight Begins With Quality Maintenance On The Ground.
User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 7, posted (5 years 1 month 6 days 17 hours ago) and read 6813 times:

A pilot once told me its part of a visual ice detection aid used when needed on the ground...during the flight they serve no purpose...j...I don't have a picture but they look like (yaw strings on a glider located in a yellow triangle , outlined by a dashed black line)

User currently offlineMax Q From United States of America, joined May 2001, 4470 posts, RR: 19
Reply 8, posted (5 years 1 month 6 days 16 hours ago) and read 6794 times:

Yes,

I think some Airlines, including Cal installed a 'heating pad' in the vulnerable area. This was a while after I had left the Aircraft but I remember seeing some controls / lights etc in the cockpit while jumpseating.



The best contribution to safety is a competent Pilot.
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 9, posted (5 years 1 month 6 days 16 hours ago) and read 6784 times:



Quoting Max Q (Reply 8):
I think some Airlines, including Cal installed a 'heating pad' in the vulnerable area. This was a while after I had left the Aircraft but I remember seeing some controls / lights etc in the cockpit while jumpseating.

The heater blanket can be seen in this picture:

View Large View Medium
Click here for bigger photo!

Photo © Daniele Saracco



The strings can be seen in this photo:

View Large View Medium
Click here for bigger photo!

Photo © PRM



User currently offlineTWAL1011727 From United States of America, joined Mar 2006, 626 posts, RR: 0
Reply 10, posted (5 years 1 month 6 days 16 hours ago) and read 6781 times:



Quoting Max Q (Reply 8):
I think some Airlines, including Cal installed a 'heating pad' in the vulnerable area.

Delta did and they call it a "Heater blanket."
Their installed on the inside (inboard only) upper surface of both wing tanks.

Delta used to use 2 different ways of checking for them.
One was the "Tactile surface check." This was a kinda non-slip painted covering
that they would run a pole across it.
If it was rough than there was no ice. If smooth - de-icing was necessary.

The other (AIRC now it was used in conjuction with the above test.)was to burn fuel from the
wing tanks down to no lower than 4000lbs in each wing(on average they used 5000 lbs.)
Then burn from the center tank. This was called the "alternate fuel burn" method.

Believe it or not we have had ice build up here in Melbourne FL.
But since Delta doesn't do de-icing here we have to use "solar de-icing"

KD


User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 11, posted (5 years 1 month 6 days 15 hours ago) and read 6768 times:



Quoting TWAL1011727 (Reply 10):
Believe it or not we have had ice build up here in Melbourne FL.
But since Delta doesn't do de-icing here we have to use "solar de-icing"

The ice on forms on the wing because the fuel is cold soaked when at altitude. Then when the aircraft descends and lands, particularly in humid climates, the cold fuel lowers the temperature of the wing skin enough to freeze the condensation.

On most aircraft this ice (frost) forms on the lower surface of wing and removal is not required. However, because the DC-9 wing is thin enough to allow the frost to form on the upper wing surface, the frost must be removed by the heater blankets or prevented from forming, by the movement of the strings.


User currently offlineMax Q From United States of America, joined May 2001, 4470 posts, RR: 19
Reply 12, posted (5 years 1 month 6 days 13 hours ago) and read 6728 times:



Quoting 474218 (Reply 11):


The ice on forms on the wing because the fuel is cold soaked when at altitude. Then when the aircraft descends and lands, particularly in humid climates, the cold fuel lowers the temperature of the wing skin enough to freeze the condensation.

On most aircraft this ice (frost) forms on the lower surface of wing and removal is not required. However, because the DC-9 wing is thin enough to allow the frost to form on the upper wing surface, the frost must be removed by the heater blankets or prevented from forming, by the movement of the strings.

Good description, except the 'frost is not prevented from forming' by the movement of the strings. That would be completely ineffective !


The strings are there merely as an indication that ice has / has not formed in the critical area. If they can be moved there should not be any ice 'overcoating' them preventing their movement. If they cannot you probably have ice.



The best contribution to safety is a competent Pilot.
User currently offlineAirframeAS From United States of America, joined Feb 2004, 14150 posts, RR: 24
Reply 13, posted (5 years 1 month 5 days 20 hours ago) and read 6574 times:



Quoting 474218 (Reply 9):

Thanks for the pics. The second pic you posted shows something like static wicks sticking out. Are they really static wicks?



A Safe Flight Begins With Quality Maintenance On The Ground.
User currently offlineDALMD88 From United States of America, joined Jul 2000, 2546 posts, RR: 14
Reply 14, posted (5 years 1 month 5 days 17 hours ago) and read 6531 times:



Quoting AirframeAS (Reply 13):
Thanks for the pics. The second pic you posted shows something like static wicks sticking out. Are they really static wicks?

They are not static wicks, they are strings. If you can move them with a stick on the ground you not have ice. The ultimate low tech indication system.


User currently offlineAirframeAS From United States of America, joined Feb 2004, 14150 posts, RR: 24
Reply 15, posted (5 years 1 month 5 days 14 hours ago) and read 6497 times:



Quoting DALMD88 (Reply 14):
....they are strings.

I don't see the strings but I do see the red sticks sticking out of the wing.....



A Safe Flight Begins With Quality Maintenance On The Ground.
User currently offlineBrenintw From Taiwan, joined Jul 2006, 1634 posts, RR: 1
Reply 16, posted (5 years 1 month 5 days 14 hours ago) and read 6494 times:



Quoting AirframeAS (Reply 15):
I don't see the strings but I do see the red sticks sticking out of the wing.....

I can assure you those are strings  Smile Those are exactly what my original question was about ... and I spent the entire hour-long flight watching them flap in the wind. They're simply red nylon-like pieces of string attached to the wing.



I'm tired of the A vs. B sniping. Neither make planes that shed wings randomly!
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17030 posts, RR: 67
Reply 17, posted (5 years 1 month 5 days 14 hours ago) and read 6485 times:



Quoting Brenintw (Reply 16):
and I spent the entire hour-long flight watching them flap in the wind.

Next time, may I recommend a book.  Wink



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineBuyantUkhaa From Mongolia, joined May 2004, 2899 posts, RR: 3
Reply 18, posted (5 years 2 weeks 2 days 16 hours ago) and read 5893 times:



Quoting AirframeAS (Reply 6):
Do we have a picture of this part in question on the M80 wing so I can get a better idea of what is being talked about?

See also the pics in this thread: Funny Orange Cords On Top Of MD88 Wing (by BuyantUkhaa Jul 9 2006 in Tech Ops)

..where I asked the same question as the OP.



I scratch my head, therefore I am.
User currently offlineRwessel From United States of America, joined Jan 2007, 2346 posts, RR: 2
Reply 19, posted (5 years 2 weeks 1 day 23 hours ago) and read 5765 times:
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Quoting AirframeAS (Reply 13):
The second pic you posted shows something like static wicks sticking out. Are they really static wicks?

The four red strings attached to the yellow triangles in the foreground are the nylon strings being talked about. Out past the aileron, there are four or five static wicks (I can't quite see the one right on the wingtip clearly enough). One just past the aileron, then a cluster of three or four closer to the wingtip.


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