Aeronautics and astronautics – Aircraft – lighter-than-air – Airship and helicopter sustained
Reexamination Certificate
2003-01-02
2004-12-28
Carone, Michael J. (Department: 3641)
Aeronautics and astronautics
Aircraft, lighter-than-air
Airship and helicopter sustained
C244S024000, C244S012200
Reexamination Certificate
active
06834829
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to vertical lift rotary wing aircraft and, more particularly, to vertical lift aircraft having an enclosed rotary wing.
2. Brief Description of the Related Art
Vertical lift rotary wing aircraft are generally characterized by a main rotor blade forming a rotary wing for the aircraft and rotatable within a horizontal plane for forcing air downwardly to overcome the force of gravity and create vertical lift capable of rendering the aircraft airborne. Conventional rotary wing aircraft, such as helicopters, typically include a cabin or fuselage, a flexible main rotor blade mounted to the cabin, a tail rotor, vertical and horizontal stabilizers and landing gear. The cabin ordinarily contains an operator control area, a storage area and an engine compartment. The main rotor blade, which comprises the rotary wing for the aircraft, conventionally includes a plurality of main rotor blade members extending radially to a main rotor shaft. The main rotor blade members typically rotate about a central longitudinal axis of the main rotor shaft in a horizontal plane perpendicular to the central longitudinal axis of the main rotor shaft. The main rotor shaft is typically oriented with its central longitudinal axis perpendicular to the ground or other surface on which the landing gear is supported when the aircraft is not in flight. The controls for conventional vertical lift rotary wing aircraft normally comprise a vertical directional control system, a horizontal directional control system and a rotational directional control system. The vertical directional control system typically comprises a collective control stick, usually located at the left hand of the pilot or operator, connected to pitch controls located about the main rotor shaft to control vertical movements of the aircraft. Ordinarily the pitch controls mechanically connect the collective control stick to the main rotor blade to effect changes in the pitch of the main rotor blade symmetrically to vary or alter vertical lift. The horizontal directional control system typically comprises a cyclic control stick, normally located at the operator's right hand, for controlling the horizontal direction of the aircraft. In many cases, horizontal directional control is effected via control rods connected to swash plates located on the main rotor shaft. The rotational directional control system typically comprises rudder foot pedals for operating the tail rotor to control yaw, i.e. rotation of the aircraft about its vertical axis, during slow flight or hovering.
Conventional rotary wing aircraft, primarily helicopters, exhibit noise, vibration, turbulence, a lack of safety and limited forward speed due to inadequacies in the main rotor blade control systems and the need to compensate for the differential effect of the wind on advancing and retreating main rotor blade members during forward flight. In conventional rotary wing aircraft such as helicopters, the horizontal directional control system usually requires a complicated system located about the main rotor shaft and which acts by reducing the pitch of each main rotor blade member on one side of the aircraft and increasing the pitch on the other side of the aircraft within a single rotational cycle, i.e. one complete rotation of the main rotor blade, to provide more lift in a desired direction. As a result, the potential for lift is negated or wasted on one side of the aircraft, causing a dynamic imbalance. The main rotor blade members thusly do not operate at maximum efficiency and power in that a significant amount of lift is lost from the total lift generated by the main rotor blade when effecting horizontal directional changes for the aircraft. In addition, vibration, turbulence and noise are created due to the main rotor blade members changing their pitch as they rotate. Since the main rotor blade in conventional rotary wing aircraft is not isolated from the relative wind, the main rotor blade exhibits flapping due to the differential speed between the advancing and retreating main rotor blade members caused by the relative wind meeting the advancing and retreating main rotor blade members during forward flight. Flapping of the main rotor blade inhibits lift and produces turbulence, vibration and noise. Also, the speed at the tips of advancing main rotor blade members must generally be reduced to a speed which, when combined with the speed of the relative wind, does not exceed the speed of sound. The need to reduce the advancing main rotor blade member tip speed decreases lift and further contributes to noise, vibration and turbulence. The turbulence, vibration and noise characteristic of conventional rotary wing aircraft contributes to pilot fatigue and stress, thereby limiting pilot endurance and increasing the chance for pilot error. The decreased centrifugal force resulting from a lowering of the main rotor blade tip speed increases coning (dihedral) of the main rotor blade plane and thusly impairs the stability of the main rotor blade plane with a concomitant reduction in lift. The requisite reduction in main rotor blade member tip speed requires that the overall speed of the aircraft also be reduced. Since each main rotor blade member does not have a constant pitch throughout all rotation angles, each main rotor blade member does not contribute its entire force to increasing lift during both hovering and forward movement.
Various types of vertical lift rotary wing aircraft have been proposed, as represented by U.S. Pat. No. 1,724,226 to Sorensen, U.S. Pat. No. 2,728,537 to Elkins, U.S. Pat. No. 2,777,649 to Williams, U.S. Pat. No. 3,750,980 to Edwards, U.S. Pat. No. 3,912,201 to Bradbury and U.S. Pat. No. 5,064,143 to Bucher. The Sorensen, Williams and Bucher patents disclose rotor blades at least partly enclosed in a housing, but are characterized by heavy and/or complicated structure as well as complex operational designs. Previously proposed vertical lift rotary wing aircraft having enclosed rotary wings utilize rigid main rotor blades that lack the ability to change pitch on the main rotor blades for rapid changes in vertical movements of the aircraft and/or lack the ability to perform an emergency auto-rotation with the aircraft. In order to be maximally effective, the control devices for the main rotor blades of previously proposed vertical lift rotary wing aircraft with enclosed rotary wings must be undesirably located close to the plane of the main rotor blades. Some prior vertical lift rotary wing aircraft with enclosed rotary wings employ a rigid, centrally reinforced and weighted ducted fan system with non-variable pitch main rotor blades, and some prior enclosed vertical lift rotary wing aircraft employ rotor blade systems having non-variable pitch rotor blades supported by rollers at the blade tips. Systems of the latter type are very heavy and also produce considerable resistance to the downdraft, resulting in decreased vertical lift. Many ducted fan systems disadvantageously require complex computer-controlled directional flaps.
In view of the above, there is a need for a vertical lift rotary wing aircraft with an enclosed rotary wing and which exhibits greater lift, forward speed and safety while reducing vibration, noise and turbulence. There is also a need for a vertical lift rotary wing aircraft with an enclosed rotary wing comprising a flexible main rotor blade of variable pitch to achieve rapid changes in vertical movements while horizontal directional control is accomplished without asymmetrical changes in pitch of the main rotor blade members which cause a dynamic imbalance. There is a further need for a vertical lift rotary wing aircraft with an enclosed rotary wing and permitting higher main rotor blade tip speed, permitting the pitch of each main rotor blade member to remain at the same setting through a single cycle, and reducing main rotor blade coning or dihedral.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention
Carone Michael J.
Semunegus L.
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