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What is the purpose of the piece of string taped to a glider canopy? Is it effectively a turn coordinator, but then what advantages would it have over a gauge such as the ones fitted in powered aircraft?

rbp
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Steve
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2 Answers2

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Yes, the yaw string on the canopy of a glider is there to show you whether or not you are coordinated, especially during turns. It indicates the relative wind, so will be straight unless the glider is slipping or skidding, in which case it will swing to the left or right.

For those not familiar with them, here is an image that shows one:

Glider yaw string

According to Wikipedia, they are also used on other aircraft (even jet fighters and the U-2!) although they are used in almost every glider.

Now, the advantages that it has over an actual instrument installed in the panel are numerous:

  • It is directly in your line of sight while looking outside, so you don't have to look at the instrument panel to see if you are yawing.
  • It is more sensitive
  • It reacts faster to changes
  • It is cheaper
  • It is lighter
  • It doesn't require electricity (or even an electrical system on the glider)
  • It costs far less to maintain
  • It is easy to recognize when it fails (it's either there or not)
Lnafziger
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  • @Lnafziger The strings on the wings serve the same purpose? How are they different than the one on canopy? – Farhan Apr 07 '14 at 21:34
  • @Farhan I haven't seen one on a wing. Do you have a picture? – Lnafziger Apr 07 '14 at 21:59
  • @Lnafziger A video is worth a thousand pictures! Here you go. – Farhan Apr 07 '14 at 22:40
  • @Lnafziger Picture. I have seen strings in the Cessna course. – Farhan Apr 07 '14 at 22:41
  • @Farhan Ahhh, they use those during certification flights so that they can observe the airflow over the wing. You won't normally see those! – Lnafziger Apr 08 '14 at 00:12
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    Here's one on an F-14D! You can see it just above the radome. http://www.navy.mil/management/photodb/photos/060922-N-1129M-017.jpg – Rhino Driver Feb 09 '15 at 18:53
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    It doubles as a weather indicator: If String is wet, its raining. If String is White, it is snowing. If String is stiff, it is freezing. If String is Dark, it is night-time. :) – abelenky Feb 09 '15 at 22:05
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    @abelenky if string is smoking, you're on fire. – Rhino Driver Feb 10 '15 at 00:04
  • The slip-skid ball is a level with ball instead of bubble. It does not require electricity, is cheap, simple and reacts fast. It measures something different, but glider can't have asymmetric thrust, so the quantities should be well correlated. – Jan Hudec Feb 10 '15 at 10:31
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    @JanHudec Well, I'm not sure that I would call it cheap or simple when comparing it to a small length of string. :) – Lnafziger Feb 10 '15 at 17:01
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On wings they are called tufts, and are a means of 2D-flow visualization. The yaw string just shows the yaw angle at a single location.

Wikipedia has a picture with tufts attached to a winglet Winglet with attached tufts of an KC-135A