Patent Application
20220073195
A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.
The present disclosure relates generally to the fields of mechanical drive systems, and in one exemplary aspect, the present disclosure is directed to methods and apparatus for driving components associated with mobile craft such as vertical short takeoff and landing (VSTOL) aircraft.
One general drawback of such prior art rack and pinion systems is their relatively high level of friction (and friction losses). Such friction reduces the longevity and reliability of such systems over time, and the losses create inefficiencies as far as power consumption for the motive source (e.g., electrical power, combustible fuel, etc.). Helical racks (i.e., those with the teeth forming a helical or angled pattern) generally offer quieter running at higher speeds, and also higher load carrying capability due to increased tooth contact area ratio relative to a non-helical configuration; however, each of the foregoing generally require lubrication apparatus to maintain them sufficiently lubricated, especially at high speeds.
Moreover, backlash (due the typically necessary level of clearance between the rack 104 and the driving “pinion” 106) can be problematic, especially in cases where transient loading is experienced; e.g., stop/start or fast/slow operational modes which change frequently. Such backlash can produce significant wear over time, thereby reducing efficiency and load capability of the mechanism with time if not constantly lubricated.
The foregoing limitations of prior art rack-and-pinion type drive systems are particularly evident in the context of applications where weight and reliability are critical, such as for use in aircraft. High reliability (a general prerequisite for any critical aircraft system) in rack-and-pinion systems effectively mandates a high level of lubrication, as well as very durable materials (such as the foregoing high-strength alloys). For instance, a broken rack tooth may render the mechanism inoperable (e.g., due to slippage/lack of engagement of the teeth by the pinion, or the broken tooth wedging itself in the mechanism and jamming it. Moreover, in the event of a tooth failure or other catastrophic failure during operation, there is generally no backup system available; especially in weight-sensitive applications such as aircraft, carrying a redundant system (e.g., a second rack and pinion mechanism) is weight-prohibitive.
The lubrication systems necessary to support operation of such high-strength components at high speed add appreciable weight to an already heavy system (e.g., via seals, the weight of lubricant), and any other ancillary components needed to effect lubrication). As such, these prior art approaches are not optimized for applications where both weight and reliability are critical.
Accordingly, improved solutions are required for applications such as e.g., VSTOL. Such improved solutions should ideally provide a reduced need for lubrication systems and components, and concurrently a high degree of reliability.
The present disclosure satisfies the aforementioned needs by providing, inter alia, improved methods and apparatus for driving components, such as within vertical short takeoff and landing (VSTOL) or other aircraft applications.
In a first aspect of the disclosure, a drive apparatus is described. In one embodiment, the drive apparatus comprises: at least one drive element comprising a plurality of roller elements disposed around a periphery of a rotatable member, the rotatable member configured to be driven by a motive force; and at least one driven element comprising a plurality of teeth configured to engage respective ones of the plurality of roller elements, the at least one driven element comprising an at least approximately circular shape.
In one variant, the drive apparatus is configured for use in a vertical short takeoff and landing (VSTOL) apparatus having at least one rotating ring comprising a plurality of airfoils disposed radially around an outer perimeter of the at least one rotating ring, the at least one rotating ring coupled to the at least one driven element.
In one implementation thereof, the at least one drive element comprises first and second drive levels, each of the first and second drive levels having a plurality of the roller elements disposed around a periphery of the rotatable member; and the at least one driven element comprises first and second driven elements, each of the first and second driven elements comprising a plurality of teeth configured to engage respective ones of the plurality of roller elements associated with the respective ones of the first and second drive levels.
In another variant, a common drive mechanism is used to drive two contra-rotating rings.
In another aspect of the disclosure, a vertical short takeoff and landing apparatus is disclosed. In one embodiment, the apparatus comprises one rotating ring with airfoils. In another embodiment, multiple (e.g., two) contra-rotating rings with attached airfoils are used, in conjunction with a power source, and a self-contained motor and drive system. The contra-rotating rings with attached airfoils rotate about the center axis of the apparatus and generate lift, and are each driven by the drive mechanism referenced above (e.g., upper and lower separate drive mechanisms.
In one variant, the capability of generating lift primarily from ambient air currents is introduced. This allows the vehicle to, inter alia, stay aloft with minimal or even no energy consumption, and utilize only minimal drive mechanism engagement.
In a further aspect of the disclosure, methods of operating the drive apparatus are described. In one embodiment, the method includes detecting failure of one of a plurality of drive levels, and selectively configuring another of the plurality of drive levels to engage in place of the failed level.
In another embodiment, the method includes detecting a load state for one of a plurality of drive levels, and selectively configuring another of the plurality of drive levels to engage in tandem with the engaged level so as to distribute or balance load across the levels.
In another aspect of the disclosure, a lift generating mechanism is described. In one embodiment, the mechanism comprises at least two contra-rotating rings having a plurality of airfoils disposed on each. In one variant, the airfoils may individually (or in unison) change pitch or attitude. In another variant, the airfoils may also extend radially from the rings so as to increase the effective diameter of the apparatus.
In another aspect, methods and apparatus for selective disengagement/re-engagement of one or more ring/driver component sets is disclosed. In one embodiment, the methods and apparatus use differential tooth sizing on rings, with selectively variable angular relationship between the individual rings. In another embodiment, clutched or “freewheeling” drive levels are used. In yet another embodiment, retractable rollers are utilized.
Other features and advantages of the present disclosure will immediately be recognized by persons of ordinary skill in the art with reference to the attached drawings and detailed description of exemplary embodiments as given below.
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Reference is now made to the drawings, wherein like numerals refer to like parts throughout.
In one aspect, the present disclosure provides methods and apparatus for mechanically driving components in a desired direction, such as in a moving craft. In one embodiment, the craft comprises a vertical or short takeoff and landing (VSTOL) aircraft comprising one or more rotating rings having airfoils disposed around a periphery thereof. In one variant, the one or more rings are driven by a multi-level drive apparatus having a plurality of angularly offset (i.e., in azimuth) roller-based drive levels, and a plurality of corresponding angularly offset driven members (e.g., rings), the plurality of driven members coupled to e.g., the at least one rotating ring. Depending on configuration, one or more of the driven rings can be engaged with its corresponding drive level so as to achieve desired levels of load (and load balancing), reduced noise, and/or failure redundancy.
Advantageously, use of this arrangement provides enhanced reliability over prior art approaches, as well as opportunities for selective load balancing. Moreover, comparatively heavy lubrication components such as seals and liquid lubricants are obviated, and the drive components themselves can be fabricated at least partly from lighter weight materials, thereby also saving weight when applied to the host craft.
Exemplary embodiments are now described in detail. While these embodiments are primarily discussed in the context of a manned or unmanned VSTOL aircraft or drones, it will be recognized by those of ordinary skill that the present disclosure is not so limited. In fact, the various aspects are useful for aircraft (whether vertical short takeoff and landing or otherwise) and other craft in a variety other contexts.
Furthermore, while the disclosure is discussed primarily in the context of generating lift in a gaseous fluid medium such as the earth's atmosphere, it will be recognized by those of ordinary skill that the architectures and principle disclosed herein could be readily adapted for use in other operating environments, such as liquids, with the discussion using gaseous mediums merely being exemplary.
It will also be recognized that while particular dimensions or angular relationships may be given for the apparatus or its components, the apparatus may advantageously be scaled to a variety of different sizes, depending on the intended application. For instance, the disclosure contemplates a small table-top or even hand-held variant which may be useful for e.g., drone usage. Likewise, a large-scale variant is contemplated, which may carry a living being such as a human, one or more sensors and even weapons (such as e.g., Hellfire precision guided munitions or the like), have greater loiter and altitude capabilities, etc. This design scalability is one salient advantage of the apparatus.
Referring now to
In one embodiment, the rings are effectively identical to one another, but as discussed in greater detail below, each is angularly offset from one another (i.e., rotated a prescribed number of degrees in azimuth such that the teeth 205 are also angularly offset relative to each other when viewed from above (see
The rings 204 are driven by a corresponding multi-level drive element 203, which rotates around a central rotational axis 202 which is in one embodiment normal to the plane of the rings 204. The drive element is driven by e.g., a DC electric motor (not shown), and includes a plurality of levels 206a-206c corresponding to the plurality of rings 204. Each level 206 contains a plurality or respective rollers 208a-208c, which are each configured as roller-bearings in one embodiment. Use of roller bearings allows for inter alia, wear and load distribution and reduction of friction, which add longevity and reliability to the mechanism as a whole. Specifically, each roller 208 can roll as it engages corresponding surfaces of the ring teeth, and hence frictional movement of the (two) surfaces is minimized.
As can be appreciated, the relationship between the rollers 208 and the teeth 205 on any given level may be identical; e.g., the roller spacing centerline-to-centerline (as reflected by θ1 304 and θ2 302 in
However, the present disclosure also contemplates embodiments where the cross-level spacings for both rollers (along with roller diameter) and teeth may vary, in effect providing a variable gear ratio for each different level.
In the embodiment (shown in
The foregoing design effectively provides additional surface area of engagement between the rings and rollers (as a whole), akin to a prior art helical approach, yet without the proportional friction produced by such helical arrangement. In the exemplary embodiment, the teeth 205 are “straight cut” to correspond to the perpendicular roller cross-section and axes of the respective drive element, and ring (and hence tooth) width may be adjusted by design (along with relative angular spacing or offset of the teeth and rollers) so as to provide the desired degree of engagement area for the calculated maximum load. As such, while a three-level design is shown in
It will also be appreciated that tooth shape or profile within the plane of the ring(s) 204 may be varied to provide desired performance and qualities. While a symmetric “bell curve” shape with circular cross-section troughs (corresponding to the circular cross-section of the rollers) is shown in
In some embodiments, the rings 204 (and even their corresponding drive rollers 208) can be fabricated from high-strength composite or polymeric material (e.g., Delrin® AF, which is a combination of PTFE fluorocarbon fibers uniformly dispersed in Acetal/Delrin resin). The PTFE (aka Teflon) adds inter alia, a “slipperiness” to the material, thereby further reducing lubrication requirements. Other materials may be used as well, such as e.g., other combinations of materials such as ETFE (Tefzel) and Polyoxymethylene (POM), and even ceramics (such as Zirconia Oxide (ZrO2)). Surface-hardening may also be employed where applicable to increase hardness and durability of e.g., ring teeth 205 and rollers 208. In that weight is critical, hardness is also critical, in that harder teeth/roller surfaces can utilize less material to produce the same “strength”, thereby also allowing for weight reduction.
In other embodiments, different ones of the “levels” of drive 203 and rings 204 may be selectively engaged or disengaged, for instance by (dynamically) varying the angular relationship of one or more of (i) the drive rings 204 to each other, and/or (ii) the drive levels 206 and rollers 208 to other levels/rollers of the same drive element 203 so as to effect a variety of desired functions. For example, it may be desirable to adjust the proportion of load being carried by each of the rings 204 in
When engagement and load-carrying by all three rings is needed, the second and third rings can be “advanced” (and then retained in fixed relationship to each other and the first ring) such that their teeth contact their respective level of roller sets 208b, 208c, thereby causing them to carry increased load. This approach can obviously be applied to the remaining N−1 rings (after the first) of an N-ring system individually, or with the N−1 remaining rings ganged together and operating in unison for advancement/retarding of their relative timing. It will be appreciated that similar effect can be accomplished by using e.g., smaller diameter rollers on for instance the second and third drive levels 206 (in place of different tooth geometry), or a combination of the foregoing can be used.
In another approach, the rollers of any given level 206 of the drive mechanism 203 can be disengaged, such as where each level of the drive mechanism is independently rotatable. In this case, each unloaded level can “freewheel” on its axis of rotation 202 when not engaged (i.e., not mechanically coupled to drive shaft or other driven level(s) 206 of the drive element 203), and then when loading is desired, that level can be coupled (e.g., via friction clutch mechanism or other approach which enables selective coupling/uncoupling) such that the now-locked level carries load in tandem with others fixed coupled to the drive shaft. In this approach, no alternative tooth or roller geometry as in
In yet a further approach, the rollers of each selectively operable level 206 of the drive mechanism 203 can be configured for selective disengagement from their rings via retraction of the rollers radially toward the motive source drive shaft/axis 201 (see
It will be appreciated that while the various embodiments shown and described herein utilize a drive mechanism and ring teeth disposed on an interior region of the rings, such mechanism may be disposed external to the rings (i.e., with the teeth and drive levels on an exterior periphery of the rings), and in fact combinations of interior//exterior drive may be used as well. In one such variant, each ring includes teeth on both an interior periphery (as in e.g.,
Moreover, the two drive elements may be driven from a common motive source (e.g., a common electrical DC motor), and may also be driven in a prescribed fixed relationship to one another (through e.g., a lightweight gearbox), or alternatively may be “clutched” such that some relative movement or slippage may occur.
Consider another such implementation, wherein two stacked rings 204 are utilized, one toothed on its interior periphery, and one toothed on its outer periphery. Respective drive elements 203 may be used therewith, each selectively engaged or disengaged depending on load, component integrity/failure status, or other considerations.
Each of the airfoils generally has a curved shape such that it is capable of generating lift while being rotated through the surrounding air. Accordingly, as the upper and lower rings of the apparatus 700 spin around a central axis, the airfoils create lift (or alternatively downdraft, or negative lift, depending on the orientation of the airfoils as discussed infra). Each of the airfoils includes a generally curved or rounded leading edge and a narrower trailing edge portion. In the embodiment illustrated, the upper airfoils curved leading edge is positioned such that the upper rotating ring will generate lift by rotating in a counterclockwise direction (when viewed from above). Conversely, the lower airfoils curved leading edge is positioned such that the lower rotating ring generates lift by rotating in the opposite direction (i.e. clockwise). While a specific configuration is shown, it is appreciated that the leading edges for the upper and lower airfoils could be reversed such that an opposite rotation (i.e. clockwise rotation for the upper airfoils and counterclockwise rotation for the lower airfoils) will generate lift for the VSTOL apparatus.
In operation, the VSTOL apparatus of
As the upper and lower rings rotate in opposite directions and are essentially identical in construction in this embodiment (albeit in a reversed orientation), the combined motion of the rings generates no net torque on the apparatus when the upper and lower rings are rotated at the same speed. This is useful in that additional rotors, or rotors oriented in an orthogonal orientation (such as that seen in conventional helicopters) are not necessary in order to provide counter rotation. In addition, by varying the relative speeds of the counter rotating rings, a net torque can be generated, thereby allowing the VSTOL apparatus to rotate about a central (vertical) axis, again without necessitating an additional rotor.
In the illustrated embodiment, each of the airfoils 706 is independently articulated, such as e.g., using mechanisms described in the previously incorporated prior patent applications. This articulation allows for control of lift, attitude, pitch, lateral translation, rotation, and other aspects.
In addition, the multiple rings allow for increased lift capability, because they allow for more points for lift generation. Furthermore, as will be appreciated later in the specification, the coordination of the upper and lower airfoil elements leads to a synergistic improvement of lift capacity. Considerations related to this coordination of upper and lower airfoils (including ring spacing, airfoil shape, rotational speed, etc.) can aid in effective airfoil/ring design that e.g., maximizes upward lift.
It can also be appreciated that advantages from gear reduction (e.g., between the output shaft of the drive source, such as a motor or engine, and the drive applied to the rings) can easily be leveraged using the contra-rotating ring design described herein. In fact, the rings themselves can act as the main reduction gears given that the drive system of the VSTOL apparatus is located entirely within the circumference of the rings.
It can also be appreciated that the airfoils can comprise flaps, slats, or other extensible control surfaces that can be expanded or contracted to change the shape of the airfoils. The change is shape can be used to reduce or increase the lift achieved through the airfoils. Moreover, deicing can be achieved by altering the shape of the airfoils, potentially loosening built-up ice.
In yet another variant, the airfoils are substantially deformable in shape via internal mechanisms. Unlike the “flap” variant referenced above (which basically exaggerates the shape of the airfoil by extending the tail portion outward so that the leading edge to tail edge distance increases), the actual curvature of the airfoil can be altered mid-flight so that the Bernoulli effect (and/or other aerodynamic properties) are altered as desired. In one implementation, the outer surface of the airfoils comprises a substantially pliable polymer “skin” laid over a frame, the latter being mechanically deformable in shape by way of one or more articulated joints. Yet other approaches will be recognized by those of ordinary skill given the present disclosure.
Other potential implementations may utilize airfoil flaps that can be extended or retracted to change the shape of the airfoils. Through this airfoil extension and contraction, the aerodynamic cross-section of the apparatus can be altered to facilitate lift via e.g., ambient air currents.
As yet another option, the airfoils may be constructed so as to have a changing pitch/curvature as a function of radial position. For example, in one such variant, the pitch or curvature of the airfoil near the root about which it rotates may be one value, while the curvature changes as the distal (outward) end of the airfoil is approached; i.e., as if one grasped the end of the airfoil and twisted it so as to distort its shape. Such varying curvature may provide desired attributes in certain applications; e.g., greater lift as a function of rotational or angular velocity.
A key advantage of the VSTOL apparatus is that is can also be operated in such that it utilizes air currents to generate lift. This leads to improved performance in both the duration that the apparatus can be deployed and the range over which it can operate. The disc shape of the rings and fuselage aide in overall glide and lift. Therefore, this VSTOL apparatus design is particularly well suited for operation based solely on air currents.
Lift is also generated in certain conditions by impingement of moving air against the upward or downward tilted airfoil exposed surface. This feature is particularly useful when the apparatus is in “loiter” mode, wherein the rings (and airfoils) are minimally rotating or not rotating, and the VSTOL apparatus is in effect acting somewhat like a kite. In such loiter mode, the operator (or onboard/remote computer controller) acts to maintain the attitude of the aircraft at a prescribed angle of attack relative to the prevailing winds, so as to generate sufficient lift to maintain the craft's altitude.
For extremely long-term operation, the motors/drive system driving the rings (and in some cases even articulating the airfoils) are turned off, and the VSTOL apparatus fully depends on air currents for lift and balance. However, with little more energy usage the pitch, extension, and expansion of the airfoils (as well as the position of aforementioned “centered” mass) can be adjusted to control the lift and balance of the VSTOL apparatus. This increases the flexibility of this operational mode.
Finally, the motors driving the rings can be placed in a low power consumption mode to further assist the ambient air currents in the generation of lift. Running the rotors would still lead to significant energy/fuel consumption. However, in an adjustable low power consumption mode, a wide range of air current speeds can be used to assist in the generation of lift. In this fashion, effective use of power and fuel economy can be achieved.
Hovering capabilities and low turning radii allow for operation of the VSTOL apparatus in a crowded airspace, or one with hostile countermeasures or munitions. For example, operation at low altitude in an urban environment will present numerous obstacles (buildings and power lines etc.). To avoid these obstacles, traditional fixed wing aircraft would have to travel too slowly to generate sufficient lift and still negotiate around these obstacles. Thus, the VSTOL apparatus is well suited for surveillance or tracking missions through such airspace. Similarly, when over hostile territory, the craft can readily “viff” (a maneuver utilized by e.g., Harrier VSTOL pilots to rapidly slow or accelerate sideways/upwards/downwards using vectored thrust nozzles) so as to avoid an incoming missile, projectiles, other aircraft, etc. This can be accomplished by, in one variant, rapidly shifting its center of mass to the desired side, or alternatively rapidly changing the pitch of the airfoils on one or both rings so as to rapidly change altitude.
It will be recognized by those of ordinary skill that when using such a concentric ring approach, one or both of teeth spacing and number of teeth (as well as corresponding roller spacing as measured along a circumferential arc between rollers) must be varied so as to accommodate the increased radius (and hence circumference) of each successive ring moving outward from the center. In one variant, a cylindrical multi-level drive element is used (not shown), wherein constant roller spacing between levels is used to correspond to constant tooth size and spacing on each ring, with each ring simply having varying numbers of teeth based on its circumference. In other embodiments, tooth geometry and roller spacing are varied, such that each ring has different characteristics in terms of e.g., load capability, friction, etc. (for instance, tooth spacing and roller spacing are increased or decreased as ring radius increases). Myriad other variants will be recognized by those of ordinary skill given the present disclosure.
It will also be appreciated that in any of the “dual airfoil ring drive” variants discussed above (i.e., those of
Referring now to
In the method 1000 of
At step 1503, a drive component or system failure is detected (such as failure of a driven ring 204 or drive level 206), via e.g., vibration sensing, noise sensing, reduction in outer ring 702, 704 angular velocity, acceleration (consistent with e.g., instability or vibration), motor current draw, and/or other mechanism. If the failure is not catastrophic (e.g., a broken tooth wedges itself in the gearing/drive element such that further operation is impossible), then the failed ring/drive level can be “swapped out” for another (step 1505) by e.g., advancing one or more of the unloaded rings in relative timing, extending retracted second/third level rollers, de-clutching the first drive level from the drive shaft, etc. as previously described. For instance, if a tooth breaks off of the first ring 204a, then that ring can be retarded (or other advanced) so as to reduce or eliminate load on the broken ring. It will be appreciated that in the case of a static (non-dynamically variable) embodiment with none of the above-described adjustment/retraction features, this process occurs effectively automatically, since all of the N rings are engaged at least to some level constantly, and hence loss of a few sequential teeth on the first ring will result in, when that region of the ring reaches the drive element, load being assumed by the remaining ones of the N−1 remaining rings.
At steps 1505 and 1507, the damaged or failed ring may also be “disengaged” if desired (after the e.g., N−1 other rings are engaged) using the same type of approach as above; e.g., retraction of its rollers, retarding of its relative angular position/timing, etc., depending on how the drive mechanism is configured (e.g., with additional lash on its teeth, retractable rollers, clutch drive mechanism levels, etc.). Alternatively, the failed ring may simply be left to operate (albeit in reduced capability depending on the type of failure).
It will be appreciated that rings 204 or other components may be selectively retired due to e.g., wear as well. For instance, where the teeth 205 of a ring 204 wear or lose shape over time due to normal loading, the ring can be selectively reduced in load or even completely unloaded. As such, a form of wear leveling can be achieved; in the event that e.g., three given rings 204a, 204b, 204c of a drive mechanism wear unevenly, they can be increasingly loaded/unloaded commensurate with their relative wear. For example, if Ring 1 wears much more heavily than Ring 2, which wears more heavily than Ring 3 (for whatever reason), the rings can be adjusted slightly in relative timing/azimuth so that Ring 3 assumes most load, Ring 2 assumes the next highest load, and Ring 1 the least, so as to balance the wear more evenly.
In the method 1600 of
At step 1603, a need to increase or distribute loading to others of the rings 204 is detected (such as a load increase fed back through the airfoils, meeting a stress limit on the solo operating ring 204, etc.) via e.g., reduction in outer ring 702, 704 angular velocity, motor current draw, output of a stress/strain sensor on the loaded ring, increase in motor RPM demanded (e.g., via a control system input to increase rotational RPM), and/or other mechanism. The non-engaged ring/drive level(s) can be engaged (step 1605) by e.g., advancing one or more of the unloaded rings in relative timing, extending retracted second/third level rollers, de-clutching the first drive level from the drive shaft, etc. as previously described. It will be appreciated that in the case of a static (non-dynamically variable) embodiment with none of the above-described adjustment/retraction features, this process occurs effectively automatically, since all of the N rings are engaged at least to some level constantly, and hence load is naturally distributed effectively equally across the different rings under all load conditions, especially since each driven ring 204 is coupled to an outer airfoil ring 702, 704 and hence under load.
It will be recognized that while certain aspects of the disclosure are described in terms of a specific sequence of steps of a method, these descriptions are only illustrative of the broader methods described herein, and may be modified as required by the particular application. Certain steps may be rendered unnecessary or optional under certain circumstances. Additionally, certain steps or functionality may be added to the disclosed embodiments, or the order of performance of two or more steps permuted. All such variations are considered to be encompassed within the disclosure disclosed and claimed herein.
While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made by those skilled in the art. The foregoing description is of the best mode presently contemplated of carrying out the principles and architectures described herein. This description is in no way meant to be limiting, but rather should be taken as illustrative of the general principles of the disclosure. The scope of the invention should be determined with reference to the claims.
This application claims priority benefit of U.S. Provisional Patent Application Ser. No. 63/047,056 filed Jul. 1, 2020 and entitled “DRIVE APPARATUS AND METHODS FOR USE” which is incorporated herein by reference in its entirety. This application is generally related to subject matter contained within co-owned U.S. patent application Ser. No. 13/675,707 filed Nov. 13, 2012 and entitled “Methods and Apparatus for Vertical Short Takeoff and Landing,” Ser. No. 15/179,859 filed Jun. 10, 2016 and entitled “Methods and Apparatus for Vertical Short Takeoff and Landing and Operational Control,” and Ser. No. 15/654,482 filed Jul. 19, 2017 and entitled “Apparatus for Providing Rail-Based Vertical Short Takeoff and Landing and Operational Control,” each of the foregoing which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63047056 | Jul 2020 | US |
