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The yaw/slip thread (merged) aka Aerodynamics 101

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The yaw/slip thread (merged) aka Aerodynamics 101

Old 7th Sep 2004, 05:08
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yaw string or slip string

please help

should a yaw string not be called a slip string since as far as i can tell it shows sideslip not yaw ???????

thanks
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Old 7th Sep 2004, 05:09
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sideslip indicator

i have a photograph of the sideslip indicator in concorde...

does anybody know of any other types (ME) that have them fitted

thanks
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Old 7th Sep 2004, 05:12
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is it yawed or yawing

please help

in a perfectly balanced level turn is a aircraft yawed or yawing

thanks
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Old 7th Sep 2004, 05:21
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3 topics on the same subject! Are you actually looking for an answer or just trying to increase your post count?

Mutt.
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Old 7th Sep 2004, 06:21
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The simple answer is neither.

If you yaw in a turn you start to sideslip so you are no longer balanced.

You can do an untidy flat turn, wings level, by yawing.
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Old 7th Sep 2004, 06:39
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Sideslip Indicator not to be confused with a balance indicator is a rare breed.

Sometimes seen on a test aircraft fitted with a vane on a boom to measure the slip, away from the influence on the arflow by the aircraft itself.

Any multi having engines outside of centre line will be sideslipping during straight flight when there is any imbalance of thrust.

Sideslipping means more drag would have been crucial for a Concord so it was probably used as an aid in precise directional trimming.

Can ex Concordians confirm?
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Old 7th Sep 2004, 07:06
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In a(balanced) left turn the application of left rudder will cause a Yaw to the left producing a Skid to the right.
Conversely application of right rudder will cause a Yaw to the right producing a left Slip .
Notice in both cases application of rudder caused a YAW which resulted in two different states,hence it is called a yaw string.

Hope that helps.

ODR.
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Old 7th Sep 2004, 07:18
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I would interpret the word yawing to mean having a component of angular velocity about its yaw axis. An aircraft in a perfectly balanced level turn is therefore yawing (as well as pitching a little).
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Old 7th Sep 2004, 07:22
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This morning PPRuNe is somewhat OVERYAWED......
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Old 7th Sep 2004, 07:47
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catchup ...

Well done, that man ..
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Old 7th Sep 2004, 07:57
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When you are in a perfectly balanced turn, you will develop an angle of bank. This means the yaw axiz leans into the turn so although you are changing direction, with the anglo of banko means you are no yawo (unless you el-slippo or el-skiddo).

compre?
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Old 7th Sep 2004, 07:59
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The sideslip indicator in Concorde was used primarily when operating with one or two engines inoperative.

To achieve zero sideslip in the asymmetric case, the climb out would be flown using around 2-3 bank into the live engines.

This was done to minimise drag and thus maximise aircraft performance.

The gliding fraternity use a piece of cotton, stuck to the outside of the canopy to achieve the same result, but on Concorde it tended to come off in the cruise, so a sideslip indicator it had to be!

Trimming in normal flight was done primarily by moving fuel around, both across the aircraft from wing to wing, as well as the more well known fore and aft transfer.

Ideally, a CG position of 59% MAC was achieved, with zero sideslip, zero rudder deflection and down elevon.

Regards

Bellerophon
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Old 7th Sep 2004, 09:08
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As you're not in a 90 degree bank, there's still rotation around the yaw axis if you are turning in the horisontal plane, i e yaw.

Regards,
Fred
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Old 7th Sep 2004, 09:35
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Hi Fred

Thats the thing, the horizontal plane (angle of bank) is tilted over directly in proportion to the yaw in a perfectly balanced turn. No yaw.
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Old 7th Sep 2004, 09:40
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Ah yes but isn't the yaw axis being rotated in the turn at the same rate as the rate of turn.? Hence no yaw. Yaw slip is showing!

Fires up the thought processes a bit !!
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Old 7th Sep 2004, 10:11
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Certainly does but... because the yaw reference is the centerline which, in a balanced turn, should be changing direction at the same rate as the plane itself.
from grc.nasa.gov:


The yaw axis is perpendicular to the wings and lies in the plane of the aircraft centerline.
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Old 7th Sep 2004, 13:07
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Bellerophon

Sorry - any multi, not including those with centre line engines, having ANY measure of asymmetric thrust will be sideslipping in straight flight whether wings level or banked.

When banked the moment of the horizontal component of lift acts around the lateral centre of pressure to balance the moment of the asymmetric thrust around the same lateral centre of pressure.

Weight does not play a part, except in manoeuvre, as one cannot have a resolved portion of the weight through 90 degrees.

Sounds like the sideslip indicator on Concord was a con.

I would like to be proved wrong!!
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Old 7th Sep 2004, 13:12
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In a PERFECTLY balanced turn there is no yaw, slip, or skid at the centre of gravity. Now, here comes the hair-splitting bit - Forward and aft of the C of G the (presumably) non flexible fuselage is slightly skidding, being outside of the ideal turn radius for it's dimensions. No yaw is involved.

Somehow, I don't think that the future of aviation as we know it rests on this one.
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Old 7th Sep 2004, 17:59
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In a PERFECTLY balanced level turn we are rotating in pitch such that when we level out we are pointed in a different direction.
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Old 7th Sep 2004, 18:05
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Just keep the ball in the middle, Bloggs!

Except for the steady heading sideslip when asymmetric - or zero sideslip with constant 2-3 deg bank for max climb perf when asymmetric. Something which was never a problem in aeroplanes with civilised amounts of engines and thrust!
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