Climb and dive valve

A climb and dive valve for aircraft fuel tanks comprises a body 110,120 with an outer fluid channel 111 passing axially through it. An outer closure element 130 is arranged to open and close the outer fluid channel 111, and an outer bias element 136 is configured to bias the outer closure element 130 to a closed position. The outer closure element 130 further comprises an inner fluid channel 131 passing axially through it and in fluid communication with the outer fluid channel 111. An inner closure element 140 is movable relative to the outer closure element 130 to open and close the inner fluid channel 131, and an inner bias element 146 is configured to bias the inner closure element 140 to a closed position. The outer bias element 136 and the inner bias element 146 are configured to bias their respective closure elements in opposite directions. The valve may also comprise two interacting flap members (Figs. 4-6).