A drive shaft assembly comprising a first shaft and a second shaft is disclosed. The second shaft is axially translatable from an engaged configuration with the first shaft at one limit of its travel to a disengaged configuration from the first shaft at the opposite limit of its travel. Engagement of the first and second shafts is via cooperating helical splines provided thereon. The helical splines give rise to a disengaging axial force on the second shaft in a fault condition in which a driving torque is applied from one of the first and second shafts to the helical splines in a rotational direction tending to unscrew the helical splines. Consequently when the second shaft is in the engaged configuration the disengaging axial force translates the second shaft to the disengaged configuration.