A lockout system for an aircraft having a rotor assembly. The lockout system includes a drive shaft coupled to and rotatable with the rotor assembly, a nonrotating airframe structure disposed proximate the drive shaft and a lock assembly having first and second lock members. The first lock member is rotatable with the drive shaft and includes a plurality of bearing assemblies. The second lock member is coupled to the nonrotating airframe structure and includes a cradle having a plurality of asymmetric slots each with a leading ramp and a trailing stop. The lock assembly has a disengaged position in which rotation of the drive shaft is allowed and an engaged position in which each of the bearing assemblies is seated within one of the asymmetric slots to prevent rotation of the drive shaft. The lock assembly is actuatable between the engaged and disengaged positions.