BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates generally to vertical take-off and landing (VTOL) fixed wing aircraft and propulsion units therefor.

Description of Related Art

Transportation is fundamental to connect people, business and services. Since the early days of aviation, designers and engineers in both the commercial and military aerospace fields have envisioned fixed wing aircraft capable of taking off from a runway no larger than its own shadow, and then transitioning to high speed forward flight. However, the reality of vertical take-off and landing (VTOL) flight for high performance commercial aircraft and military fighters have proven to be a perplexing and obsessive goal. Helicopters and Autogyros, both types of VTOL but of non-fixed wing aircraft types, are often deemed too fragile, too slow and too vulnerable for safe air commerce and/or aerial combat.

The well-known “VTOL Wheel” produced by AHS International of Fairfax, Va. together with its Vertipedia database list some forty-five various aircraft types within the broad category of VTOL capable. Within these forty-five aircraft types, some fifteen various thrust options and some four different propulsion methods can be observed. To date there has been several successful high-speed military VTOL aircraft. These include the MD AIBAE A V-8 Harrier and Lockheed Martin F-35 incorporate rotating jet nozzles thrust vectoring and/or lift fan technology.

Notwithstanding past and present accomplishments in the VTOL field, there is a continuing need and desire to design, develop and demonstrate a VTOL fixed wing aircraft with exceptional performance in vertical and cruise flight and operational capability through transition from vertical to forward flight. A particular goal for VTOL fixed wing aircraft is sustained high-speed forward flight in the range of about ˜200 kt and 400 kt.

Many such aircraft seeking to meet these design criteria utilize open-exposed rotors or propellers that rotate between VTOL and flight modes. However, there is an ever-present concern that open-exposed rotors or propellers within the human safety zone could be hazardous and create excessive noise issues. In hostile military environments, open-exposed rotors or propellers are also more vulnerable to flying metal shrapnel and small arms fire. Another downside to rotating engines or propellers is that rotation changes the thrust point. Rotating mechanisms, and the dedicated power supplies that are needed to provide the mechanical rotating transition, add significantly to center of gravity issues and make it very difficult to sustain controlled flight.

Many such aircraft seeking to meet high design criteria such as these utilize open, exposed rotor blades and propellers that rotate between VTOL and flight modes. These commonly include tilt rotor and tilt wing designs. However, there is an ever-present concern that open, exposed rotor blades and propellers pose serious safety hazards. Additionally, complex rotating turbo-machinery is subject to increased malfunctions and failures due to the inherent physical loads with rotating center of gravity (CG) limits and aerodynamic instabilities. The one engine out envelope is of critical concern, requiring heavy complex cross shafting mechanisms. An adverse consequence inherent in the design of tilt wing, tilt motor aircraft is that high rotor blade forces tend to interact violently on the leading edge of the main wing. The prop wash beating the leading edge can produce exterior skin and interior structural (spar) cracking and fatigue issues.

There is therefore a need in the art for improved VTOL fixed wing aircraft that are safe and efficient, that are capable of extended ranges, higher speeds, greater payloads, lower noise signatures, and lower carbon footprints and reduced operating costs.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of this invention a fixed wing assembly is provided for an aircraft capable of vertical take-off and landing (VTOL) maneuvers and forward flight. The assembly comprises a main wing having an upper surface and an opposite lower surface. The upper surface is configured to produce lift by accelerating the free flow of air thereover relative to the lower surface. The main wing has a leading edge and a trailing edge. The main wing has a front spar and an aft spar. The front and aft spars are arranged generally parallel to one another. A combination VTOL and forward flight propulsion system is supported from the main wing. The propulsion system includes at least one articulating propulsor pair operatively stationed on the main wing. The articulating propulsor pair comprises a leading-edge propulsion unit adjacent the leading edge of the wing and a trailing-edge propulsion unit adjacent the trailing edge of the wing. A leading unit mounting structure supports the leading-edge propulsion unit for articulated movement between VTOL and forward flight positions. The leading unit mounting structure includes a leading swing arm operatively connected to the leading-edge propulsion unit. The leading unit mounting structure includes a leading linear actuator operatively connected to the leading-edge propulsion unit. A trailing unit mounting structure supports the trailing-edge propulsion unit for articulated movement between VTOL and forward flight positions. The trailing unit mounting structure includes a trailing swing arm operatively connected to the trailing-edge propulsion unit. The trailing unit mounting structure includes a trailing linear actuator operatively connected to the trailing-edge propulsion unit. The leading swing arm has a leading swing pivot disposed adjacent the front spar. The leading linear actuator has a leading actuator pivot disposed adjacent the aft spar. And the trailing swing arm has a trailing swing pivot disposed adjacent the aft spar. The trailing linear actuator has a trailing actuator pivot disposed adjacent the front spar.

The novel arrangements of propulsion units and their corresponding mounting structures improve the structural integrity achieved by locating the several pivots nearly directly on the front and aft spars. The strategic placement of these pivots also enables large degrees of rotation, which allows for improved control in VTOL and forward high-speed flight. In VTOL mode, the propulsion units produce a low-pressure area above the wing thus adding to the overall lift ability of the aircraft. In VTOL mode, the propulsion units produce a high-velocity airflow downward to produce lift. In VTOL mode, the arc of the propulsion units can be optimized within the lower width of the wing structure to assure maximum capabilities for producing a low-pressure area above the wing upper surface. Still further, the novel mounting structures enable strategic positioning of the propulsion units in both VTOL and forward flight modes so that prop wash can be maintained clear of the aircraft structures. In both high and low speed forward flight, the pull and push of airflow is designed with respect to the airfoil of the wing so that airflow is over and under creating a beneficial “blown wing” effect.

According to a second aspect of this invention, a combination VTOL and forward flight propulsion system is provided of the type to be supported from the main wing of an aircraft. The main wing has a leading edge and a trialing edge and an upper surface and a lower surface. The propulsion system comprises a leading-edge propulsion unit adapted for placement adjacent the leading edge of a wing. A trailing-edge propulsion unit is adapted for placement adjacent the trailing edge of the wing. A leading unit mounting structure supports the leading-edge propulsion unit for articulated movement between VTOL and forward flight positions. The leading unit mounting structure includes a leading swing arm operatively connected to the leading-edge propulsion unit. The leading swing arm has a leading swing pivot. The leading unit mounting structure includes a leading linear actuator operatively connected to the leading-edge propulsion unit. A trailing unit mounting structure supports the trailing-edge propulsion unit for articulated movement between VTOL and forward flight positions. The trailing unit mounting structure includes a trailing swing arm operatively connected to the trailing-edge propulsion unit. The trailing swing arm has a trailing swing pivot. The trailing unit mounting structure includes a trailing linear actuator operatively connected to the trailing-edge propulsion unit. And a spar box mechanically interlocks the leading swing pivot and the leading actuator pivot and the trailing swing pivot and the trailing actuator pivot as a unit.

The spar box can be designed to function as the main support structure that carries the high loads of the articulating propulsion units.

According to a third aspect of this invention, a propeller is adapted for operative attachment to the output shaft of a propulsion motor for a fixed wing aircraft assembly. The propeller comprises a hub defining a rotary axis. A plurality of blades extend radially from the hub. Each blade terminates at a distal tip. An annular propulsor thrust ring is concentrically disposed about the hub. The propulsor thrust ring joins each of the tips of the blades into a monolithic structure. The propulsor thrust ring has an aerodynamic cross-sectional profile as taken in a radial plane intersecting the rotary axis of the hub. The aerodynamic profile has an interior surface and an exterior surface. The interior and exterior surfaces of the aerodynamic profile converge at leading and trailing rims. The aerodynamic profile has a PTR angle of attack (AOA) that is generally parallel to or diverging relative to the rotary axis. And, the trailing rim has a thrust nozzle that conically converges airflow toward the rotary axis at a thrust angle (⊖) measured with respect to the PTR angle of attack (AOA).

The propulsor thrust ring captures radial air leakage and its thrust nozzle vectors that radial air flow into valuable thrust. The propulsor thrust ring also captures and deflects undesirable sounds and heat that may otherwise be directed toward the fuselage. As a result, the propeller of the present invention is more efficient and quieter than traditional open bladed propeller designs. Furthermore, the propulsor thrust ring eliminates induced drag around the distal tips of the blades. The propulsor thrust ring represents a safety improvement over traditional open bladed propeller designs. The propulsor thrust ring adds structural integrity to the propeller by connecting the distal tips of the blades. Similarly, the low vibration harmonics will be improved by the propeller of this invention. For all of these reasons, the propeller is desirable as an ultra-efficient propulsor having a much lower noise signature than traditional designs. As a result, the propeller may be designed to rotate at slower RPM while producing more thrust at lower noise levels. The propulsor thrust ring has an airfoil shape that produces a low-pressure area around the propeller adding to its overall efficiency.

