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The Rockwell B-1b uses pairs of airbrakes/spoilers on each wing in replacement of ailerons for the lateral control of the aircraft. Was there a particular advantage to this because of its variable swept wings or because of its mission role being a high altitude supersonic bomber?

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Doing away with ailerons helps to reduce the wing area by allowing to extend flaps over the full span. This is not unique to the B-1, other swing wing airplanes (F-111, Su-24, MRCA Tornado) also use spoilers together with differential deflection of the horizontal tail surfaces for roll control. With full-span flaps, the desired minimum speed can be achieved with a smaller wing area as opposed to the partial-span flaps of a wing with ailerons.

Another reason is to reduce wing loads. The B-52 is rolled by using spoilers, not ailerons, in order to reduce wing torsion and extend the structural life of the wings.

With fly-by-wire systems that allow to vary control deflections and functions depending on speed and angle of attack, roll control by differential tail deflection has become ubiquitous, even on airplanes with conventional ailerons.

To my knowledge, the first design which extended trailing edge flaps over the full span and relied on spoilers for roll control was the Messerschmitt M37 (early version of the Bf-108) which was designed to compete in the FAI Challenge International de Tourisme 1934.

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  • $\begingroup$ Never mind, maybe already asked. $\endgroup$
    – quiet flyer
    Commented Feb 2, 2022 at 20:29
  • $\begingroup$ My first, (and seemingly most obvious...) impression would be to reduce or eliminate adverse yaw caused by induced drag out at the end of the upgoing wing when you don't have a tail surface to counter it. Is this not a concern? $\endgroup$
    – Michael Hall
    Commented Oct 31, 2022 at 18:14
  • $\begingroup$ @MichaelHall Yes, this is also a concern. If you have the massive vertical of a B-52, however, maybe less so. The B-2 opens its split ailerons halfway so it can reduce drag one one and increase it on the other side when rolling. $\endgroup$
    – Peter Kämpf
    Commented Oct 31, 2022 at 19:49
  • $\begingroup$ Thanks Peter. Is it enough concern to include in your answer? ;) $\endgroup$
    – Michael Hall
    Commented Oct 31, 2022 at 22:22

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