Abstract: A helicopter's main rotor blades are removably attached to a hub, which is rotatably mounted on a mast. The base of the mast is attached to the helicopter's body by unthreaded, expandable bushing bolts. When inserted, the bolts' centerlines lie in a plane which perpendicularly intersects the axial centerline of the mast. The mast is hollow and encases a drive shaft. Splines at one end of the drive shaft removably engage splines on the engine transmission. The hub has a removal fitting for engaging an end of the drive shaft. When the mast is detached and pulled apart from the helicopter body for storage, the removal fitting forces the drive shaft splines to disengage from the tnansmission splines, and keeps the drive shaft inside the mast while the mast is being removed. The main rotor blades' pitch is controlled by a plurality of pitch control linkages. Each linkage is comprised of a first part connected to the mast and a second part connected to the helicopter body.

Abstract: A roadable helicopter according to various aspects of the present invention comprises a vehicle that drives like a conventional car in its road configuration, and converts to fly like a helicopter in its flight configuration. The operator of the helicopter only needs to press a button to initiate the conversion from one configuration to the other. To facilitate the flight configuration, the helicopter is preferably equipped with a dual, coaxial counterrotating rotor system to provide lift, propulsion, and control in the flight configuration. In the road configuration, however, the rotor system automatically folds into a rotor bay formed in the rear of the helicopter. The roadable helicopter may also include an automatic control/stability/navigation system that permits fully automatic flight.

Abstract: A low-profile transportation and storage assembly is readily substitutable with a conventional pair of skid landing gear. The low-profile transportation and storage assembly includes a front auxiliary crosstube having low-profile wheels attached to opposing ends of the front auxiliary crosstube, and a rear auxiliary crosstube having low-profile wheels attached to opposing ends of the rear auxiliary crosstube. Both the front auxiliary crosstube and the rear auxiliary crosstube are readily substitutable with the pair of skid landing gear of a conventional helicopter. A pair of front saddle mounts and a pair of rear saddle mounts secure the front crosstube and the back crosstube of the pair of skid landing gear to the helicopter. The pair of front saddle mounts and the pair of rear saddle mounts can be quickly removed from the aft crosstube and the forward crosstube by removal of expandable bushing fittings of the saddle mounts.

Abstract: A piezoelectric actuator includes a plurality of linearly axially expandable hard piezoelectric rods located between two plates and are distributed about a central twistable core fastened between the plates, with the axis of the rod skew to the axis of the core, resembling a squirrel cage. The actuator produces a twisting movement between the plates, responsive to voltage induced expansion of those piezoelectric rods. Fly by Wire aircraft control is realized with the actuator in various systems providing all electric control of aerodynamic surfaces, including an electronic helicopter swashplate by which the effective pitch of the main rotor blade is controlled.

Abstract: An engine control system for a helicopter having at least one engine is provided, including an electronic engine control unit for each engine and further including a manually operated system for backing up each electronic engine control unit in the event of a failure thereof or for permitting optional manual engine operation. The engine control system includes at least one collective pitch stick and at least one twist grip rotatably mounted on the collective pitch stick. Each twist grip includes a normal (NORM) position within the range of the operating arc which is coincident with a detent. The system includes means for electronically actuating the detent to retract when the twist grip is rotated out of the NORM position into a manual operating mode, so that the electronic disablement of the detent permits an operator to smoothly operate the twist grip through the operating arc when the engine control system is in a manual control mode.

Abstract: A universal joint for use in a pitch cone rotor system in a helicopter is comprised of crossed lift beams, one beam of which is coupled to the rotor hub and the other beam of which is coupled to the driven rotor shaft. The two crossed lift beams are coupled to each other through a cruciform case. The cruciform case in turn is coupled to each of the crossed lift beams by means of a plurality of flexures. The flexures and cruciform case are made of composite fiber materials and the flexures are soft enough to permit angular and translational deflections of the crossbeams with respect to each other thereby tending to smooth out and reduce sudden changes in rotor speed between the shaft and rotor system and thereby tending to make rotor speeds more uniform. The crossed lift beams are further coupled together at the center of their crossing by a flexible elastomeric tension link which conducts rotor loads between the two beams when the rotor develops negative lift loads on the ground and in flight.

Abstract: A fiberglass-epoxy flexbeam extends from tip to tip of each opposed blade pair, carrying the blade centrifugal forces so that none of the centrifugal loading is carried by the hub. The primary load-carrying connector between the flexbeam and the hub is a set of elastomeric pads. These provide a soft mount between the flexbeam and the hub to keep the primary bending moments within the flexbeams where the filaments are designed to accommodate them. The elastomeric pads are also effective in isolating the hub from chordwise loads which include the steady driving torque and the "C" mode and "S" modes of coriolis vibration. The elastomeric hub mount damps these vibrations and tunes their frequencies to values well separated from the rotor frequency.