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Fig. L55 Conceptual explanation for spanwise pressure gradient on swept-back
wings.
of air accelerated downward by the vortex sheet. This _solved the problem of lift
deficiency associated with swept-back wings. Thus, a new concept of controlled
{low separation came into existence that represented a departure from the time-
honored concept of attached flow. Under this new concept, a wing is designed for
attached fiow at supersonic cruise conditions and atlow speeds; the flow is allowed
to separate at the leading edge and generate the beneficial vortex lift. We will study
more about slender delta wings later in the text.
An example ofthe aircraft d6esign based on the controlled fiow separation concept
is the Anglo-French Concorde, which is the first supersonic commercial aircraft
with a slender ogee-delta wing planform.
Swept-forward wings. Historically, the first airplane to use the forward-
swept wing17 was the Junkers Ju 287, which was ajet-powered German bomber
aircraft during World War II. The wing had a forward sweep of 25 deg. Then in
1961, Messerschmitt of Germany produced the HFB 320 Hansa aircraft, which
also had forward-swept wings. After these brief appearances, the forward-swept
wing disappeared from the horizon until the Grumman X-29 research aircraft made
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56 PERFORMANCE, STABILITY, DYNAMICS, AND CONTROL
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