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leading edge flap/slat thing......

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Old 26th May 2004, 14:11
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Question leading edge flap/slat thing......

On a few airliners I have seen a flap of some sort being folded down below and a little bit behind the leading edge of the wing. Its hinged in front.

As I fly helicopters I have a fairly good understanding of aerodynamics, but this one has me stumped. Is it some sort of speed brake? Lift dumping device?

Would like to know....

Timts
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Old 26th May 2004, 14:41
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Hi there!
Its is a leading edge flap, called a Krueger flap. Aerodynamically not very ellegant but effective enough. It is also a relatively simple construction and therefore light. Not as efficient as a slat.

Hope this answwers your question..
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Old 26th May 2004, 15:49
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TIMTS

As Md has said the Kreuger flap is simple and effective although it does not look right which is probably what has got to you! The way I have it in my head is that deploying the Kreuger lowers the stagnation point quite markedly. This means that the amount of airflow above the stagnation streamline is increased and has to travel further on its way over the upper surface and so Mr B works better.

If the stagnation streamline is new to you let me know and I could post a simple diag
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Old 26th May 2004, 21:33
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Thanks

Thanks guys

No..that makes perfect sense!

I guess it is the same Krueger that is behind the little metal strip on the trailing edge of the horizontal stabilizer on the Sikorsky S-76...

Any truth to the rumour that it was invented by accident by a nascar driver trying to win some races? A guy named Krueger...
Thats the story told at when I got my licenses

Thanks again guys
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Old 26th May 2004, 23:22
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Also, because it doesn't work as effectively as other leading edge devices, the stall occurs earlier on the section where the Krueger flap is located. That is why you will find it on the inboard section of the leading edge if the manufacturer has decided to utilise it.
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Old 27th May 2004, 00:01
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TIMTS - I believe you are confusing the Kruger with the Gurney. This is a surface normal to the flow, usually at the rear of an aerofoil. It has the effect of increasing the effective camber of the aerofoil and therefore lift/downforce.

It was first seen in F1 as a means to circumvent the rules on wing sizing. The team came up with some bizarre excuse to pass it off as nothing but the other teams caught up and 'borrowed' the idea too.
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Old 27th May 2004, 04:40
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.. and, if my recollection is correct, a similar device was tried as a flight test fix on a light turboprop twin about 25 years ago to fix a long stab problem .. killing the two front seaters and critically injuring the FTE down the back ...
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Old 27th May 2004, 08:13
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John Tullamarine

It wasn't at Tullamarine though. It was Avalon!!

I still see the surviving FTE.
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Old 27th May 2004, 08:59
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aye .. and the FTE and I know each other extremely well ... had circumstances been a little different it could conceivably had been me in the aircraft instead of Pat ...
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Old 27th May 2004, 10:30
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This was a Kruger Flap thread a while back, and it has an interesting link as well.

Go here

L337

P.S. Sadly the link is broken
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Old 27th May 2004, 14:17
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I stand corrected

Gurney flap it is...

found a good quote
"Before it was tested every self-respecting aerodynamicist could name lots of reasons why it wouldn't work....after it was tested they all tried to explain why it did..."
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