Nope !!! Believe oit or not it actually increases drag
To reduce the airflow on top of the wing to flow towards the fuselage, and under the wing from flowing towards the wingtip. These airflows create the wingtip-vortex!
Nope
A small hint: it has something to do with stalls and boundary layers !!
Wing fences have been used on swept wing aircraft for fifty years. The MiG-15, one of the earliest examples of their use, incorporated two fences on each wing. The F-86 used them as well. Fences can also be seen on more recent production aircraft like the Fiat G 91 and the BAe Hawk and
Harrier.
Despite their use on aircraft fying at supersonic and near supersonic speeds, wing fences are also of use on low speed swept wing aircraft such as man carrying sailplanes and RC models. The
Akaflieg Braunschweig SB-13 and a rendition of Hans-Jurgen Unverferth's CO8 by Glyn Fonteneau and Dave Camp serve as examples within those realms.
Wing fences have both an interesting history and an interesting effect.
A wing fence is nothing more than a flat plate which is attached perpendicular to the wing and in line with the free stream air flow. Wolfgang Liebe is credited as being the inventor of the device,
for which he received a German patent in 1938, during his work on the Messerschmitt Bf 109B.
The Messerschmitt Bf 109B had a rather peculiar stall. The stall initiated at the wing root, and a
cross span flow very near the leading edge then travelled outward toward the wing tip at high speed. The result of this aerodynamic behavior was that the entire wing stalled at essentially the same time, a very dangerous characteristic. Installation of a wing fence prevented the cross span flow, thus eliminating the stall problem.
That a solid plate in the path of cross span flow close to the wing surface would obstruct the flow,as was seen on the Bf 109B, may seem obvious. In actuality, however, the mechanism of
operation was more covert in that the beneficial effect was provided by the initiation of a sideslip and the resulting vortex generated by the fence.
Wing fences on swept wings have been found to be very beneficial to inhibiting the nasty stall behaviors which result from severe angles of sweep, but their operation in this environment is entirely different than on a straight wing such as the Bf 109B.
To make a long story short the wing fence will try to prevent or better say delay the wingtip stall to happen.
In fact due to the swep angle of the wings the boundary layer will be sucked from the root of the wing to the wingtip. This means that the boundary layer will be less thick at the root and hereby the outboard part of the wing is more likely to stall (separtated flow --> remember that boundary layer = turbulent zone)
Now the fence which acts like a vertical wing will help to keep that boundary layer attached on the outbpard side. Which means that the wingtip stall will be delayed.
However the inboard sides conditions will be deteriorated. That's why on many planes you find many fences next to each other. Each fence will be beneficial for the outboard side.
With difference I don't want to hear that one is located at the leading edge and the other at the trailing edge of the wing. I want to know the purpose of both devices.
The leading edge slats allow the aircraft to fly at a high angle of attack (lower speed) by accelerating the air between the slat and the wing (venturi effect). The leading edge slats allow for steep climb angles of up to 30-degrees.
The trailing edge flaps on the other had simply extend or enlargen the wing, giving it better lift capabilities at low speed.
So at low speed this means that : The slats speed up the air to make sure it sticks to the upperwing surface to prevent a stall. The flaps enlargen the wing to give it more lift to prevent the aircraft from slamming into the ground.
After all these 'harder' questions for the average spotter, I will ask one that every spotter (especially EBBR-spotters) should be able to answer.
What is the external, well visible difference between an BAe-146 and an Avro RJ ?
In other words, when one of SN's comes flying by, how will you see it's an BAe or an Avro ?
Greetz,
Andries
Last edited by Andries on 13 Oct 2005, 22:22, edited 1 time in total.
Sabena320 wrote:The Bae is shorter then the RJ in the front?
incorrect.
There are 6 different airframes in the BAe-146 and Avro Family. The BAe-146-100 and Avro RJ70 basically have the same airframe (99% the same), but then the RJ70 has newer avionics and better engines. The same goes for The BAe-146-200 andRJ 85 and for the BAe-146-300 and RJ100.
So all Avro's have this difference compared to the BAe's and it's that difference I wish to hear.
realplaneshaveprops wrote:Indeed an easy one, certainly for me. But I will pass to give the others a chance. Only when nobody can give the answer, I will do it.
Koen
Certainly an easy one for you (or any other SN technician for that matter) ! If you wouldn't know
realplaneshaveprops wrote:Indeed an easy one, certainly for me. But I will pass to give the others a chance. Only when nobody can give the answer, I will do it.
The slats speed up the air to make sure it sticks to the upperwing surface to prevent a stall.
Andries 
) found a small mistake in the question.