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Why does Concorde and many other deltas have their wings bent down?

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Concorde's ogee (ogival) wing is a smoothed-out slender double-delta.

  1. Slender wings at high angles of attack produce too much positive rolling moment in a sideslip because of the deep chord, so the tip anhedral reduces that. Another solution gleaned from early slender wing studies is the gull-wing, though structurally it's more difficult (the Boeing SST drawings show a gull-wing).

  2. Slender wings when landing are dominated by ground effect in a favorable way in terms of leveling up and lateral stability; tip anhedral helps bring the wing closer to the ground while keeping the benefits of the long landing gear—avoiding FOD ingestion, and more crucially, takeoff and landing performance, i.e. permitting a higher angle of attack in takeoff and landing than a shorter landing gear would allow.

  3. Slender wings at high angles of attack with anhedral tips move the suction peak inwards, allowing the primary vortex to not migrate too far outward, meaning it will work over a larger surface area and therefore will provide more lift.

The first two points are from a paper by Sir Morien Morgan (the father of Concorde), and the last point is from later research. During Concorde's design, some vortex lift phenomena could not be probed in the wind tunnel because the probes themselves would affect the vortices. In Morien's words, a lot of the design was "patient and often ad hoc work" with literally hundreds of wind tunnel models being tested, for example 370 variants of the leading edge were tested.

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  • $\begingroup$ That all sounds great, but there must be downsides or other planes would presumably use the same design. $\endgroup$
    – StephenS
    Dec 11, 2021 at 16:34
  • $\begingroup$ @StephenS: You mean subsonic airliners? Ogee wings are not good in subsonic cruise (efficiency wise). If you mean SSTs, the Soviet Tu-144 also had such anhedral. $\endgroup$
    – user14897
    Dec 11, 2021 at 16:37
  • $\begingroup$ You might also want to look at the Concorde's profile in flight. The wings allow significant upwards flex, removing 2/3rds of that anhedral. (absolutely none of the post-engine droop remains, while in flight) $\endgroup$
    – PcMan
    Dec 11, 2021 at 16:59
  • $\begingroup$ @PcMan: Maybe in high-speed cruise, but for subsonic in T/O, climb, approach, and landing, not really, though finding the right angle is tricky, but here's an excellent one; note how the anhedral is evident from how the engine nacelle is covered. $\endgroup$
    – user14897
    Dec 11, 2021 at 17:48
  • $\begingroup$ @ymb1 yep. And if the wing was not flexed up, but in the attitude as per the image in the OP question, you would have barely seen any of the engine at all, much less the rear nacelle of it. The wing is anhedral, definitely so. But much, much less that that image in the question suggests. $\endgroup$
    – PcMan
    Dec 11, 2021 at 19:32

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