A vertical stabilizer fin and rudder assembly (10) for use on an aircraft including a stabilizer fin (26) with airfoil surfaces and a rudder (18) with a forward margin pivotally mounted on the trailing edge of the stabilizer fin (20). The assembly is subjected to Bernoulli forces as a relatively moving airstream passes over it in a chordal direction. A fin spoiler (26) is pivotally mounted on each fin surface at a forward chordal location on the assembly (10) whereby the effective sideslip capability for the fin surfaces, when the aircraft is operated in a crosswind, is substantially increased.