What is that "wing fence" for?
 

Hi!

I was just wondering what is the purpose of that thing in the picture below:

http://www.fotosik.pl/pokaz_obrazek/...37d77d157.html

wingfence.jpg | | Fotki, Zdj?cia, Obrazki Fotosik.pl

I've seen that in Pipers (Seneca V in the picture), Beech (King Air) and couple others.

Can somebody explain me what is that for?

Reduces lateral movement of air toward the wingtip hence reduces vortex (lift induced) drag.

What is efficiency of such small device? Why it's installed only in GA aircraft? Here you can see it even with King Air BLR winglet:

Winglet Systems - BLR Aerospace

(Enlarge pics on the right side)

Google is your friend

Google doesen't say a lot about that particular device. And of course we're not talking here about winglets or proper wing tip fence (like Airbus or PZL-101A).

Google so far gives me a tip that it can be connected with shielding pilot from the lights (landing or strobe). So as you can see it differs a bit from your theory and thats why I'm asking about some evidence of your statement.

To reduce span-wise flow.

Wing fence - Wikipedia, the free encyclopedia

hardly a light twin
http://farm3.staticflickr.com/2505/3...13c933e5_z.jpg

From wikipedia link above:

"Wing fences, also known as boundary layer fences and potential fences are fixed aerodynamic devices attached to aircraft wings. Not to be confused with wingtip fences, wing fences are flat plates fixed to the upper surfaces (and often wrapping around the leading edge) parallel to the airflow. They are often seen on swept-wing aircraft. They obstruct span-wise airflow along the wing, and prevent the entire wing from stalling at once."



This is not a device which I mean. Especially the dimensions, purpose, place of installation and size...

Of course you have to know that Seneca I II and III doesn't have such "wingtip device" from my first post. It's only fitted to Seneca V.

All of them are there for the same reason. Design details dictate the size and position; determined by either modeling or flight test.

Think you might find that these " fences" on the PA's are to help prevent glare from the tip lamps entering the nearby cockpit i.e. not an aerodynamic device at all :ok:

What rubbish.

Aerodynamically - poor to nil. They don't do much harm either.

Su-25s have it too.

Glareshield.

PPRuNe at its best.

Also sometimes referred to a stall fences, these devices tend to delay aerodynamic stall on the outboard portion of the wing by creating an impediment to spanwise flow along the upper wing surface. Several 1960s and '70s swept wing bizjet types used this aerodynamic "tweak" to improve low speed characteristics including the HS125 and Falcon 20. Dassault eliminated the need for them in later wing designs. Hawker/Beech replaced stall fences with vortilons for the HS125 -1000 and 800XP models.

westhawk

I think the fence referred to in the first pic is to reduce glare for the pilot.

That's nothing to do with aero dynamics.

Its the gauge that you use to find out when to trigger the de-icing boots.

And as reds says to stop the lights blinding you

Dak Man post #7 shows you EXACTLY what the fences are for.

Fences on the upper surface of a wing are used to help reduce reverse span wise airflow which in turn, help reduce the chances of wing tip stall to occur.

For it to work as an aerodynamic fence.
It needs to be thicker than the boundary layer and extend past the point of lowest pressure.

It would have to be a bit more beefy than 2 mm plate

It is simply to reduce the glare from the aircraft lighting. If you were able to get a close look, you would see a small hole in it, which helps you see if the lights are working.:ok:

Well I read the headline in the OP and didn't look at the image. I thought we were talking about FENCES! :uhoh:

westhawk