Abstract: A vertical takeoff and landing aircraft is described in which rotors can be disposed underneath the booms. This will allow for zero downward force resulting from thrust on the aircraft and therefore greater energy efficiency. Retractable doors can shield the rotors when not in use, decreasing drag during forward flight.

Abstract: An object-oriented, hierarchical model of a computer network layered communications subsystem is implemented in a configuration database subsystem to create and maintain a configuration database and to provide configuration data to the layered communications subsystem. The layered communications subsystem is represented by a set of defined object classes, each object class corresponding to one or more functions defined at each of the communications subsystem layers, the object classes being related in a hierarchical relationship which preserves the functional relationship among the various functions in the various layers making up the layered communications subsystem.