Patent Application
20210261240
This disclosure relates in general to the field of aircraft, and more particularly, to a vertical takeoff and landing aircraft with wings and download reducing winglets.
This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
Fixed-wing aircraft, such as airplanes, are capable of flight using wings that generate lift responsive to the forward airspeed of the aircraft, which is generated by thrust from one or more jet engines or propellers. The wings generally have an airfoil cross section that deflects air downward as the aircraft moves forward, generating the lift force to support the aircraft in flight. Fixed-wing aircraft, however, typically require a runway that is hundreds or thousands of feet long for takeoff and landing.
Unlike fixed-wing aircraft, vertical takeoff and landing (VTOL) aircraft do not require runways. Instead, VTOL aircraft are capable of taking off, hovering and landing vertically. One example of a VTOL aircraft is a helicopter which is a rotorcraft having one or more rotors that provide lift and thrust to the aircraft. The rotors not only enable hovering and vertical takeoff and landing, but also enable forward, backward and lateral flight. These attributes make helicopters highly versatile for use in congested, isolated or remote areas.
Tiltrotor aircraft include proprotors that can change their plane of rotation based on the operation being performed. Tiltrotor aircraft generate lift and propulsion using proprotors that are typically coupled to nacelles mounted near the ends of a fixed wing. The proprotors rotate relative to the fixed wing such that the proprotors have a generally horizontal plane of rotation for vertical takeoff, hovering and landing and a generally vertical plane of rotation while cruising in forward flight, wherein the fixed wing provides lift and the proprotors provide forward thrust. In this manner, tiltrotor aircraft combine the vertical lift capability of a helicopter with the speed and range of fixed-wing aircraft.
An exemplary aircraft includes a wing positioned below a vertical rotor, the wing extending to an outboard end, and an anhedral winglet extending from the outboard end through an angular transition to a tip, the anhedral winglet having an external surface exposed to the rotor downwash and the external surface contoured to generate local wing lift in response to the rotor downwash.
An exemplary method includes operating an aircraft in a hover, the aircraft having a vertical rotor producing a rotor downwash directed vertically downward onto a wing extending to an outboard end, and an anhedral winglet extending from the outboard end through an angular transition to a tip, the anhedral winglet having an external surface exposed to the rotor downwash. In an embodiment the anhedral winglet generates local lift in response to the rotor downwash. A turbulence feature may be located on the external surface of the anhedral winglet to trigger turbulence in the rotor downwash on the external surface of the winglet.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of claimed subject matter.
The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.
It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various illustrative embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. For example, a figure may illustrate an exemplary embodiment with multiple features or combinations of features that are not required in one or more other embodiments and thus a figure may disclose one or more embodiments that have fewer features or a different combination of features than the illustrated embodiment. Embodiments may include some but not all the features illustrated in a figure and some embodiments may combine features illustrated in one figure with features illustrated in another figure. Therefore, combinations of features disclosed in the following detailed description may not be necessary to practice the teachings in the broadest sense and are instead merely to describe particularly representative examples. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not itself dictate a relationship between the various embodiments and/or configurations discussed.
In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “inboard,” “outboard,” “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. As used herein, the terms “connect,” “connection,” “connected,” “in connection with,” and “connecting” may be used to mean in direct connection with or in connection with via one or more elements. Similarly, the terms “couple,” “coupling,” and “coupled” may be used to mean directly coupled or coupled via one or more elements.
Aircraft 10 is illustrated as a helicopter for purposes of description, however, the aircraft is not limited to helicopters. Aircraft 10 includes, without limitation, vertical takeoff and landing aircraft, helicopters, tiltrotors, and rotorcrafts. Download reducing winglets 50 may be utilized in any aircraft that has wings located below a vertical rotor. Vertical rotor is used herein to denote rotors or fans (e.g., ducted fans) that are positioned, temporarily or permanently, above a wing.
With additional reference to
When the aircraft is hovering the pitch of the vertical rotor directs rotor downwash 22 vertically against top surface 24 of wings 14 producing a greater download than when the aircraft is in forward flight. Wing 14 and anhedral winglet 50 are configured to reduce the download produced by the rotor downwash when the aircraft is hovering.
With reference to
With reference in particular to
Turbulence feature 36 may take various forms including without limitation, surface roughness, trip strips and vortex generators. Turbulence feature 36 may be positioned at various locations on external surface 58. In an exemplary embodiment, turbulence feature 36 is located at angular transition 54. In an exemplary embodiment, turbulence feature 36 is located on external surface 58 at a position that may be identified as, or proximate to, the maximum thickness of wing 14 extending along the span.
Trip strip 36 in this example is located on angular transition 54 of external surface 58. Trip strip 36 extends generally in the longitudinal (axis X) direction and generally perpendicular to rotor downwash 22 when hovering. Trip strip 36 may be oriented to extend parallel, or generally parallel, to the forward cruise streamline 40 when the aircraft is at the maximum cruise speed and attitude. In other words, trip strip may be oriented generally parallel to the chord of wing 14. The orientation of trip strip 36 may be determined to produce the desired benefits during hover and minimize any ill effects in forward flight.
Conditional language used herein, such as, among others, “can,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include such elements or features.
The term “substantially,” “approximately,” and “about” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. The extent to which the description may vary will depend on how great a change can be instituted and still have a person of ordinary skill in the art recognized the modified feature as still having the required characteristics and capabilities of the unmodified feature. In general, but subject to the preceding, a numerical value herein that is modified by a word of approximation such as “substantially,” “approximately,” and “about” may vary from the stated value, for example, by 0.1, 0.5, 1, 2, 3, 4, 5, 10, or 15 percent.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the disclosure. Those skilled in the art should appreciate that they may readily use the disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure and that they may make various changes, substitutions, and alterations without departing from the spirit and scope of the disclosure. The scope of the invention should be determined only by the language of the claims that follow. The term “comprising” within the claims is intended to mean “including at least” such that the recited listing of elements in a claim are an open group. The terms “a,” “an” and other singular terms are intended to include the plural forms thereof unless specifically excluded.
