If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#21
|
|||
|
|||
John Galloway wrote:
It means exactly the same rudder direction you apply in any other, non spinning, yawed condition (how could it be otherwise as the string doesn't change its mode of action in a spin?). The front end of a yaw string is stuck to the canopy and if the loose end is pointing left in a spin you apply apply right rudder. Are you sure? Imagine a flat spin. If the loose end is pointing to the left, doesn't that mean yoiu are spinning to the right? So don't you want left rudder? |
#22
|
|||
|
|||
Yikes... This thread is well on its way to the top for adding confusion to a topic!! I don't even think of yaw string in terms of 'pointing'... for me it solely reflects how air is passing over it, the string always stays aligned to this airflow...and most all of the time I want to keep my ship aligned pointy end first into that same airflow. My contribution to the confusion. At 04:00 17 January 2005, Greg Arnold wrote: John Galloway wrote: It means exactly the same rudder direction you apply in any other, non spinning, yawed condition (how could it be otherwise as the string doesn't change its mode of action in a spin?). The front end of a yaw string is stuck to the canopy and if the loose end is pointing left in a spin you apply apply right rudder. Are you sure? Imagine a flat spin. If the loose end is pointing to the left, doesn't that mean yoiu are spinning to the right? So don't you want left rudder? |
#23
|
|||
|
|||
At 04:00 17 January 2005, Greg Arnold wrote:
Are you sure? Imagine a flat spin. If the loose end is pointing to the left, doesn't that mean yoiu are spinning to the right? So don't you want left rudder? You better sort that out in your head quick! Think. Start straight level and slow. Feed in full left rudder. The glider rotates (yaws) left but continues initially on the track it was going. The airflow is now coming more from the right and blows the yaw string out to the left (the slip ball, which is free to move in its tube, goes out to the right sharply because the airflow is decelerating the whole aircraft apart from it). The left wing reaches the stall, the wing drops and the angle of attack increases even further. The increase in drag on the wing causes the glider to continue rotating to the left. The glider is now sinking rapidly with the left wing more badly stalled than the right due to the rotation. This means that the glider continues to yaw and roll left. Looking from above the glider is now following a circular anti-clockwise path with the nose pointing into the circle and the tail out. The airflow is still coming more from the right (over the whole aircraft and not just forward of the centre of gravity) and the yaw string is being blown out to the left whether the nose pitches down or up into a flat attitude or not. The slip ball (and you) are trying to continue in a straight line and feel a force throwing you to the right. This is a left hand spin! The anti-spin action at this point is to reduce the yaw to the left with full right rudder; pull the string, push the ball or step on the head of the snake (sounds like a position in the Kama Sutra) as your personal mantra dictates and then move the stick forward from its central position (where I hope you placed it as the spin developed) until the wing unstalls. Now centralise the rudder before loading the wing up on the pull out or you'll be off the other way. |
#24
|
|||
|
|||
Thanks Z. Couldn't have put it better myself - in
fact I didn't! It is interesting that I have had various feed back from pilots who have applied the wrong rudder or found it difficult to instantly decide which way they were rotating in a sudden unexpected spin or knew about someone else who had reported this experience. To refocus, and taking into consideration the fact that my use the word 'opposite' has created confusion that I really didn't expect, my new improved (?) wording is: 1)The string acts laterally in the same sense in a spin as at all other times and the rudder correction for a given direction of yaw string deviation is exactly the same direction as in level flight. 2)Deciding how to correct yaw by use of a yaw string is a task that glider pilots do almost continually during flight but deciding which way the glider is rotating in a spin is a very occasional task - and one that is survival critical 3)Use the yaw string as the primary reference to decide the correct rudder to apply in the event of an unexpected spin 4)All sailplanes should have yaw strings. John Galloway At 06:00 17 January 2005, Z Goudie wrote: At 04:00 17 January 2005, Greg Arnold wrote: Are you sure? Imagine a flat spin. If the loose end is pointing to the left, doesn't that mean yoiu are spinning to the right? So don't you want left rudder? You better sort that out in your head quick! Think. Start straight level and slow. Feed in full left rudder. The glider rotates (yaws) left but continues initially on the track it was going. The airflow is now coming more from the right and blows the yaw string out to the left (the slip ball, which is free to move in its tube, goes out to the right sharply because the airflow is decelerating the whole aircraft apart from it). The left wing reaches the stall, the wing drops and the angle of attack increases even further. The increase in drag on the wing causes the glider to continue rotating to the left. The glider is now sinking rapidly with the left wing more badly stalled than the right due to the rotation. This means that the glider continues to yaw and roll left. Looking from above the glider is now following a circular anti-clockwise path with the nose pointing into the circle and the tail out. The airflow is still coming more from the right (over the whole aircraft and not just forward of the centre of gravity) and the yaw string is being blown out to the left whether the nose pitches down or up into a flat attitude or not. The slip ball (and you) are trying to continue in a straight line and feel a force throwing you to the right. This is a left hand spin! The anti-spin action at this point is to reduce the yaw to the left with full right rudder; pull the string, push the ball or step on the head of the snake (sounds like a position in the Kama Sutra) as your personal mantra dictates and then move the stick forward from its central position (where I hope you placed it as the spin developed) until the wing unstalls. Now centralise the rudder before loading the wing up on the pull out or you'll be off the other way. |
#25
|
|||
|
|||
4)All sailplanes should have yaw strings.
While watching 'Top Gun' on the boob-tube the other day...I noticed the Navy puts them on the F-14. Didn't do Maverick any good though So what is the logic for no yaw string?...I had the occasion to fly in a private two seater once, that did not have one. Some logic I did not understand about using the T+B ball instead. |
#26
|
|||
|
|||
At 06:00 17 January 2005, Z Goudie wrote:
At 04:00 17 January 2005, Greg Arnold wrote: Are you sure? Imagine a flat spin. If the loose end is pointing to the left, doesn't that mean yoiu are spinning to the right? So don't you want left rudder? You better sort that out in your head quick! Yep! We had better do some spins and observe the yawstring while it develops; I'll confess that I have never paid attention to the string while spinning. (Further comments in body of post) Think. Start straight level and slow. Feed in full left rudder. The glider rotates (yaws) left but continues initially on the track it was going. The airflow is now coming more from the right and blows the yaw string out to the left (the slip ball, which is free to move in its tube, goes out to the right sharply because the airflow is decelerating the whole aircraft apart from it). The left wing reaches the stall, the wing drops and the angle of attack increases even further. The increase in drag on the wing causes the glider to continue rotating to the left. The glider is now sinking rapidly with the left wing more badly stalled than the right due to the rotation. This means that the glider continues to yaw and roll left. I think everyone agrees to this point. Error in thought takes place once the spin starts. Looking from above the glider is now following a circular anti-clockwise path with the nose pointing into the circle and the tail out. The airflow is still coming more from the right (over the whole aircraft and not just forward of the centre of gravity) and the yaw string is being blown out to the left whether the nose pitches down or up into a flat attitude or not. The slip ball (and you) are trying to continue in a straight line and feel a force throwing you to the right. This is a left hand spin! (Here is another indicator; if you feel a force throwing you to the right you need to add right rudder) This is where the confusion begins; it is tempting to think that the glider is simply rotating about its CG without sideways movement; (it almost looks that way above 3000ft. agl). If that were the case the yaw string would switch sides because the airflow would now be from the left ahead of the CG and from the right aft of the CG. In truth, the whole glider is still sliding through the air to the right side in this left-hand spin, so the yaw string should still be to the left side. The anti-spin action at this point is to reduce the yaw to the left with full right rudder; pull the string, push the ball or step on the head of the snake (sounds like a position in the Kama Sutra) as your personal mantra dictates and then move the stick forward from its central position (where I hope you placed it as the spin developed) until the wing unstalls. Now centralise the rudder before loading the wing up on the pull out or you'll be off the other way. This mental error in not recognizing the sideways component of the spin is what accounts for stall/spin accidents on turn to final; down low the sideways movement is dramatically noticeable in a way that it is not at altitude. This is the reason pilots do not recognize a spin down low. We should emphasize this continuing sideways component in all spins and call attention to it by the behavior of the yaw string. I would like to believe that focussing on this sideways movement might prevent some future accidents. |
#27
|
|||
|
|||
I am convinced. Keeping the rule as simple as possible: "Do the same
thing to straighten the yaw string in a spin as you would do at any other time." John Galloway wrote: Thanks Z. Couldn't have put it better myself - in fact I didn't! It is interesting that I have had various feed back from pilots who have applied the wrong rudder or found it difficult to instantly decide which way they were rotating in a sudden unexpected spin or knew about someone else who had reported this experience. To refocus, and taking into consideration the fact that my use the word 'opposite' has created confusion that I really didn't expect, my new improved (?) wording is: 1)The string acts laterally in the same sense in a spin as at all other times and the rudder correction for a given direction of yaw string deviation is exactly the same direction as in level flight. 2)Deciding how to correct yaw by use of a yaw string is a task that glider pilots do almost continually during flight but deciding which way the glider is rotating in a spin is a very occasional task - and one that is survival critical 3)Use the yaw string as the primary reference to decide the correct rudder to apply in the event of an unexpected spin 4)All sailplanes should have yaw strings. John Galloway At 06:00 17 January 2005, Z Goudie wrote: At 04:00 17 January 2005, Greg Arnold wrote: Are you sure? Imagine a flat spin. If the loose end is pointing to the left, doesn't that mean yoiu are spinning to the right? So don't you want left rudder? You better sort that out in your head quick! Think. Start straight level and slow. Feed in full left rudder. The glider rotates (yaws) left but continues initially on the track it was going. The airflow is now coming more from the right and blows the yaw string out to the left (the slip ball, which is free to move in its tube, goes out to the right sharply because the airflow is decelerating the whole aircraft apart from it). The left wing reaches the stall, the wing drops and the angle of attack increases even further. The increase in drag on the wing causes the glider to continue rotating to the left. The glider is now sinking rapidly with the left wing more badly stalled than the right due to the rotation. This means that the glider continues to yaw and roll left. Looking from above the glider is now following a circular anti-clockwise path with the nose pointing into the circle and the tail out. The airflow is still coming more from the right (over the whole aircraft and not just forward of the centre of gravity) and the yaw string is being blown out to the left whether the nose pitches down or up into a flat attitude or not. The slip ball (and you) are trying to continue in a straight line and feel a force throwing you to the right. This is a left hand spin! The anti-spin action at this point is to reduce the yaw to the left with full right rudder; pull the string, push the ball or step on the head of the snake (sounds like a position in the Kama Sutra) as your personal mantra dictates and then move the stick forward from its central position (where I hope you placed it as the spin developed) until the wing unstalls. Now centralise the rudder before loading the wing up on the pull out or you'll be off the other way. |
#28
|
|||
|
|||
Duane Eisenbeiss wrote:
The above post was incomplete. Over sensitive Send button. View the string as a pointer. The forward end (the point) points at the required rudder pedal to continue the turn or stop yaw. It is impossible for the forward end to "point" at anything, since it is fixed in place by tape. The string pivots around its stationary forward end. Any "pointing" is of course done by the free aft end of the string, away from the pivotal point. Same thing as the hands of a clock. The minute hand points "right", not left, at five past twelve. If you give left rudder you will slip to the right and the string will point left. Cheers CV |
#29
|
|||
|
|||
"Stewart Kissel" wrote in message ... So what is the logic for no yaw string?... Flawed. That was easy, next?! Brent |
#30
|
|||
|
|||
CV wrote:
Duane Eisenbeiss wrote: The above post was incomplete. Over sensitive Send button. View the string as a pointer. The forward end (the point) points at the required rudder pedal to continue the turn or stop yaw. It is impossible for the forward end to "point" at anything, since it is fixed in place by tape. The string pivots around its stationary forward end. Any "pointing" is of course done by the free aft end of the string, away from the pivotal point. Same thing as the hands of a clock. The minute hand points "right", not left, at five past twelve. If you give left rudder you will slip to the right and the string will point left. So do you tell students that the wind sock points to where the wind is going? Impossible or not, by using my *imagination* early in my flying career, I was able to simply and quickly make sense of what the yaw string was indicating without having to think about where the relative wind was coming from, or which pedal to push. Jeez. Shawn |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
AOPA Stall/Spin Study -- Stowell's Review (8,000 words) | Rich Stowell | Aerobatics | 28 | January 2nd 09 02:26 PM |
Spin Training | JJ Sinclair | Soaring | 6 | February 16th 04 04:49 PM |
String in the middle does not protect you from a spin | Jim | Soaring | 10 | January 30th 04 02:57 PM |
Cessna 150 Price Outlook | Charles Talleyrand | Owning | 80 | October 16th 03 02:18 PM |
AOPA Stall/Spin Study -- Stowell's Review (8,000 words) | Rich Stowell | Piloting | 25 | September 11th 03 01:27 PM |