Aerofoils

An aerofoil, comprising a central panel and lateral panels hingedly connected at each side thereof, the central panel being arranged for rotation about a central longitudinal axis, the lateral panels on the two sides being of similar cross-section and the central panel being of symmetrical cross-section about a median plane passing through said central axis at right-angles to the panel, the cross-sections of the panels being such that either one of the lateral panels can be folded inwardly to lie against the central panel leaving the other lateral panel extended, the combined panels thereby forming a non-symmetrical aerofoil in cross-section, the mirror-image of which can be provided by alternatively folding the other lateral panel, the aerofoil thus formed being adjustable relative to the prevailing air flow by rotation about said axis, the lateral panels also being foldable inwards together to meet edge-to-edge in a stowed configuration for the aerofoil wherein the meeting edges of the lateral panels in the stowed configuration are spaced from the surface of the central panel and the lateral panels provide an external surface whose profile substantially matches that of the external surface of the central panel.