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BreninTW
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MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 6:07 am

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?
 
ZBBYLW
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 6:11 am

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!
 
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BreninTW
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 6:20 am



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.
 
Max Q
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 6:26 am



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.
 
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Starlionblue
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 7:21 am



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." - John Ringo
 
113312
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 9:20 pm

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.
 
AirframeAS
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 9:24 pm

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.
 
soon7x7
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 10:02 pm

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)
 
Max Q
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 10:32 pm

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.
 
474218
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 10:50 pm



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

 
twal1011727
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 10:54 pm



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
 
474218
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Jul 27, 2009 11:33 pm



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.
 
Max Q
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RE: MD-80 Series -- Strings Tied To Wing?

Tue Jul 28, 2009 1:32 am



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.
 
AirframeAS
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RE: MD-80 Series -- Strings Tied To Wing?

Tue Jul 28, 2009 6:55 pm



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.
 
Dalmd88
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RE: MD-80 Series -- Strings Tied To Wing?

Tue Jul 28, 2009 9:28 pm



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.
 
AirframeAS
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RE: MD-80 Series -- Strings Tied To Wing?

Wed Jul 29, 2009 12:37 am



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.
 
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BreninTW
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RE: MD-80 Series -- Strings Tied To Wing?

Wed Jul 29, 2009 12:51 am



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.
 
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Starlionblue
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RE: MD-80 Series -- Strings Tied To Wing?

Wed Jul 29, 2009 1:17 am



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." - John Ringo
 
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Buyantukhaa
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RE: MD-80 Series -- Strings Tied To Wing?

Sun Aug 16, 2009 10:56 pm



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.
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rwessel
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RE: MD-80 Series -- Strings Tied To Wing?

Mon Aug 17, 2009 4:21 pm



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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