Wing fences?
Join Date: Feb 2002
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Glider manufacturers, namely ASW and Schempp Hirth, discovered the benefits of winglets along time ago. (15-20 years ago)
They increased the max L/D of their gliders/sailplanes considerably.
Typically for the Ventus it increased from a glide angle of 1:42 to somewhere in the region of 1:48 and for the Nimbus 3 from something like 1:50 to 1:55, not quite the curvature of the earth but I think that they are still working on it !
For you boys and girls who have never flown these superb machines...
Ah well... you have all missed out !
They increased the max L/D of their gliders/sailplanes considerably.
Typically for the Ventus it increased from a glide angle of 1:42 to somewhere in the region of 1:48 and for the Nimbus 3 from something like 1:50 to 1:55, not quite the curvature of the earth but I think that they are still working on it !
For you boys and girls who have never flown these superb machines...
Ah well... you have all missed out !
Join Date: Oct 2001
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At high sub-sonic speeds the local mach number is often close to 1.0. This often occurs mid way across the elevator or at the join of elevator and rudder.
Massive seperation will occur behind the shockwave and can mean that little airflow actually touches the control surface. It therefore becomes useless which is far from a desirable characteristic!
Many high subsonic acft have vortex generators near the rudders/elevators to re-energise the boundary layer thereby maintaining control effectiveness.
Obviously above Mach 1 this a moot point but thats where the all moving tailplane comes into play.
I suspect that is what you see on the 737.
*For interests sake have a look at the very inboard leading edge on the A340/330 wing. The slats dont sit flush. There is an 6" saw-tooth/notch.
Massive seperation will occur behind the shockwave and can mean that little airflow actually touches the control surface. It therefore becomes useless which is far from a desirable characteristic!
Many high subsonic acft have vortex generators near the rudders/elevators to re-energise the boundary layer thereby maintaining control effectiveness.
Obviously above Mach 1 this a moot point but thats where the all moving tailplane comes into play.
I suspect that is what you see on the 737.
*For interests sake have a look at the very inboard leading edge on the A340/330 wing. The slats dont sit flush. There is an 6" saw-tooth/notch.
Join Date: Nov 2000
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yes eng1170
Yes, they were placed on the NG aircraft. Three evenly spaced vortilons outside the enginepylons.
My conclusion is that these perform the same task as a wingfense by generating vortexes over the wing at high AoA.
Another interesting feature that I have noted is that when the slat is extended the geometric (or was it aerodynamic) washout is enhanced.
It never occured to me that this is an excellent way to make the wing more effective over a greater speedrange as this was never covered by the aerodynamics syllabus (at least not something that my class covered).
best regards/lns
My conclusion is that these perform the same task as a wingfense by generating vortexes over the wing at high AoA.
Another interesting feature that I have noted is that when the slat is extended the geometric (or was it aerodynamic) washout is enhanced.
It never occured to me that this is an excellent way to make the wing more effective over a greater speedrange as this was never covered by the aerodynamics syllabus (at least not something that my class covered).
best regards/lns
