Krueger flaps

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Krueger flaps

Krueger flaps deployed from the leading edge of a Boeing 747 (top left and right in photo)

Krueger flaps are lift enhancement devices that may be fitted to the leading edge of an aircraft wing. Unlike slats or drooped leading edges, the main wing upper surface and its nose is not changed. Instead, a portion of the lower wing is rotated out in front of the main wing leading edge. Current Boeing aircraft, and many others, utilize this design between the fuselage and closest engine, where the wing is thickest. Outboard of the engine, slat flaps are used on the leading edge. Most early jet liners utilized Krueger flaps only, such as the B707 and B727.

Operation

While the aerodynamic effect of Krueger flaps is similar to that of slats or slots, they are deployed differently. Krueger flaps, hinged at their leading edges, hinge forwards from the under surface of the wing, increasing the wing camber and maximum coefficient of lift.^[1] Conversely, slats extend forwards from the upper surface of the leading edge.

The Krueger flaps developed for the Boeing 747 were constructed from fiberglass honeycomb material and were designed to be intentionally distorted into an aerofoil section on deployment.^[2]

History

Krüger flaps were invented by Werner Krüger in 1943 and evaluated in the wind tunnels in Göttingen, Germany.^[3] One of the earliest applications was the Boeing 367-80 in 1954.

Krueger flap operation
Slat operation

References

Notes

↑ Gary V. Bristow (2002). Ace the Technical Pilot Interview. McGraw-Hill Professional. ISBN 0-07-139609-8. Retrieved 2009-02-16.
↑ Taylor 1990, p. 114.
↑ http://books.google.de/books?id=nUMYE0Viwg4C&pg=PA193&dq=Kr%C3%BCgerklappe+Werner+Kr%C3%BCger&hl=de&sa=X&ei=9kSaUe7OGpDMsgbmnoGgCg&ved=0CDIQ6AEwAA#v=onepage&q=Kr%C3%BCgerklappe%20Werner%20Kr%C3%BCger&f=false Krueger flaps

Bibliography

Taylor, John W.R. The Lore of Flight, London: Universal Books Ltd., 1990. ISBN 0-9509620-1-5.

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