AU2017202056A1

AU2017202056A1 - Joint Box Wing aircraft configuration, offering efficiency gains through aerodynamic advantage and improved structural efficiency through its unique geometry. Resulting in an increase in lift capability, range and endurance above traditional aircraft platforms.

Info

Publication number: AU2017202056A1
Application number: AU2017202056A
Authority: AU
Inventors: Bruno De Michelis; Ron Ligeti
Original assignee: Lgt Aerospace Pty Ltd
Current assignee: Lgt Aerospace Pty Ltd
Priority date: 2017-03-28
Filing date: 2017-03-28
Publication date: 2018-10-18

Abstract

The Design of a Joined/ Box Wing aircraft incorporating features to provide stability while improving upon the efficiency and performance when compared to a traditional aircraft. The design type provides higher efficiency, a smaller relative wingspan for its improved lifting capability while maintaining adequate stability or agility tailored for specific mission requirements. Figure 1 Figure 2

Description

JOINED/ BOX WING AIRCRAFT DESIGN FOR MANNED AND UNMANNED VEHICLES

FIELD

[0001] This disclosure generally relates to Joined/ Box Wing aircraft design for Manned and Unmanned aircraft, and more particularly to the wing area ratio’s between the two wings, wingtip designs that include square and radial wingtip geometries for Joined/ Box wing aircraft

BACKGROUND

[0002] It is becoming increasingly necessary to operate long range, high payload aircraft that occupy a small footprint on the ground due to handling requirements, runway, hangar and gate size. These aircraft types include but are not limited to surveillance aircraft manned or unmanned drones, passenger and cargo aircraft. The Joined/ Box Wing technology offers significant efficiency gains and payload capability over traditional aircraft. These attributes are an enabler for the greater use of lower energy density fuels compared to traditional aircraft.

[0003] Traditionally in aircraft aerodynamic design, the largest efficiency gain is attained by increasing the aspect ratio of the wings. Wing aspect ratio is proportional the efficiency of the wing. The wing aspect ratio is usually limited by wingspan restrictions from ground handling, airport runway/ gate sizes and structural aero elasticity effects. This imparts a theoretical limit of wing area to aspect ratio for a given aircraft built in a specific material. The Joined/ Box Wing offers a greater wing area at a high aspect ratio per unit of wingspan.

[0004] Conventional aircraft are also limited by wingspan due to aero-elasticity effects such as flutter or control reversal. Traditionally aircraft add structural supports adding weight to the design to compensate for aero elasticity effects. This added structural weight eventually mitigates the benefits of the increase in aspect ratio giving a theoretical limit to the aspect ratio. Additionally the joining of the wings at the wing tips provides an increase in stiffness due to the wings coupling individual elastic loads upon each other and increasing the overall cross sectional area of the system, the result increases the natural frequency of the entire wing structure.

SUMMARY

[0005] The joint Box Wing configuration provides efficiency gains over a traditional aircraft design through utilizing a higher aspect ratio pair of wings. To overcome the aero elasticity issues the wings are joined together at the tips by either means of the first embodiment of the design using vertical “square” wingtips or the second embodiment utilizing radial wingtip structures. The wingtip structures link the two wings together creating a box type of geometry highly resistance to aero elastic flight loads. The reduction in aero elastic behavior reduces structural weight of the overall design configuration further improving efficiency.

[0006] A design of a J/BW aircraft includes determining the differential of wing area ratio’s between the wings to provide longitudinal or pitch stability. The wing area ratio’s of the front and rear wings determine agility and stall behavior. The stability parameters are set by the mission requirements of speed and maneuverability the aircraft is designed for. The first embodiment of wing area ratio shows the wing area dominant towards the rear wing for additional maneuverability providing canard style stall attributes [0007] A design of a J/BW aircraft includes determining the differential of wing area ratio’s between the wings to provide longitudinal or pitch stability. Where the second embodiment of wing area ratio shows the wing area dominated towards the front wing for additional high speed stability and conventional stall characteristics.

[0008] A design of a J/BW aircraft includes determining the differential of wing airfoil sections between the wings to provide longitudinal or pitch stability by varying the thickness and camber of the airfoils of the wings individually.

[0009] A design of a J/BW aircraft includes varying the angle of attack of the front or rear wing to modify stall behavior and longitudinal behavior. However this can reduce efficiency therefore the previous methods of longitudinal stability modification stated are the preferred method.

[0010] A design of a J/BW aircraft includes increasing the tow-in angle of the wingtips to achieve additional Yaw axis stability [0011] A design of a J/BW aircraft includes determining the outward angle of the top section of the wingtip in comparison to the lower section of the wingtip to achieve additional Lateral or Roll stability [0012] A design of a J/BW aircraft includes determining the dihedral angle of the front wing to achieve additional Lateral or Roll stability. The secondary effect of this is to provide additional ground clearance for the wingtips for takeoff and landing.

[0013] Example of Joined/ Box wing aircraft incorporating square type of wingtip design to join the wings into a box style of arrangements.

[0014] Example of a second embodiment of a Joined/ Box wing aircraft incorporating Radial type of wingtip design to join the wings into a radial wingtip style of arrangement.

[0015] A design of a second embodiment of a Joined/ Box wing aircraft incorporating Radial type of wingtip design where the airfoils of the upper and lower wings are blended together through the radial wingtip, incorporating blended airfoil sections around the median point of the radial wingtip section.

[0016] A design of a second embodiment of a Joined/ Box wing aircraft incorporating Radial type of wingtip design where the yaw control is achieved through a split multi piece rudder system or contour morphing rudders.

[0017] J/BW designs incorporating additional technologies of solar panels on wings, electric and hybrid propulsion, variable pitch propeller system that also provides thrust vectoring abilities, jet propulsion and vertical lift propulsion arrangements.

[0018] The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings.

BRIEF SUMMARY OF THE DRAWINGS

[0019] Figure 1 is a perspective view of the first embodiment of a J/ BW aircraft with square wingtips [0020] Figure 2 is a perspective view of the second embodiment of a J/ BW aircraft with radial wingtips; [0021] Figure 3 is a plan view of a J/BW in the canard configuration where the wing area ratio is predominantly increased towards the rear wing 2 when compared to the front wing 1. This figure additionally shows the tow in angle arrangement of the wingtips 7 and 8 with arrow 9 depicting angular airflow when compared to aircraft orientation; [0022] Figure 4 is a plan view of a J/BW aircraft in the conventional wing area embodiment where the wing area ratio is increased towards the front wing 3 when compared to rear wing 4, rear wing 4 shows wing sweep forward ; [0023] Figure 5 is a side view showing possible wing angle of attack changes 5 up and 6 down to modify the longitudinal stability of the design; [0024] Figure 6 Shows a front view of a square wingtip embodiment where angle 10 influences side slip airflow 11; [0025] Figure 7 is a front view of the square wingtip embodiment showing possible dihedral angle changes 12 of both front and rear wing to improve roll stability; [0026] Figure 8 is a front view of the radial wingtip embodiment showing chord line radius 16, median section point 13 and upper wing tip airfoil 14 and lower wing tip airfoil 15; [0027] Figure 9 is a front view of the radial wingtip embodiment showing a segmented wingtip control surface rudder 17 deployed, 17 could also be a singular morphing surface [0028] Figure 10 is a side view showing alternate fuselage positioning on the aircraft being low orientation 18 and mid mounted orientation 19

DESCRIPTION

[0029] When increasing the scale or size of the aircraft, the joint Box Wing configuration has the potential of providing a 25% efficiency gain over a traditional aircraft design through utilizing a higher aspect ratio pair of wings. Referring to Figure 1 to overcome the aero elasticity issues the wings are joined together at the tips by either means of the first embodiment of the design using vertical “square” wingtips or referring to Figure 2 the second embodiment radial wingtip structures. The wingtip structures link the two wings together creating a box type of geometry highly resistance to aero elastic flight loads. This box type structure braces the aero elastic loads of the individual wings to each other, the system as a whole increases cross sectional area and increases the stiffness by increasing the natural frequency of the system. The reduction in aero elastic behavior reduces structural weight of the overall design configuration further improving the efficiency.

[0030] The wing area ratio’s between the two wings determines the flying characteristics of the Joint box wing design. Referring to Figure 3 the first embodiment of wing area ratio shows the wing area ratio of 55% being dominated towards the rear wing 2, this effectively provides the front wing 1 45% of the total wing area producing a canard style behavior of the wings with regards to stability. The difference of wing area between the wings is 10% in this embodiment, this ratio can be greater however reducing the difference will start to cause longitudinal stability issues. This configuration couples with the workable center of gravity and increases the wing loading towards the front wing causing it to stall first, providing a safe canard style nose bobbing stall. This embodiment dictates that front wing 1 incorporates the elevator on the inboard trailing edge for the reasons of promoting stall due to angle of attack change upon use and distance from aircraft center of gravity. The additional characteristic of high maneuverability is presented when this embodiment of aircraft is travelling at high speeds, as with any canard aircraft the canard reduces stability proportionally at higher speeds, certain missions require the aircraft to have improve agility at speed one example pertaining to a highly maneuverable close air support ground attack type of aircraft.

[0031] Referring to Figure 4 the second embodiment of wing area ratio shows the wing area ratio of 55% being dominated towards the front wing 3 with the remainder of the wing area ratio of 45% encompassed in the rear wing. This configuration coupled with the workable center of gravity increases the wing loading towards the front wing causing it to stall first. This embodiment dictates that the rear wing 4 incorporates the elevator on the inboard trailing edge for the reasons of distance from aircraft center of gravity. The additional characteristic is of increased stability when the design is demonstrated at high speeds. This embodiment would be suited for such missions as high subsonic speed transport or surveillance aircraft.

[0032] Referring to Figure 3 the design of a J/BW aircraft includes determining the differential of wing airfoil camber and thickness between the front wing 1 of 15% and rear wing 2 of 13% to provide additional longitudinal or pitch stability if required. These thickness ratios can vary dependent on the desired characteristics of the aircraft. A change in airfoil sections between the wings will alter the critical angle of attack of each wing individually ensuring the front wing stalls first providing predictable stall behavior and pitch stability.

[0033] Referring to Figure 5 a J/BW aircraft includes varying the angle of attack of the front wing 5 or rear wing 6 to modify stall behavior and longitudinal stability behavior. By increasing the angle of attack on the front wing or decreasing angle of attack of the rear wing a differential in critical angle of attack occurs between the wings, invariably causing the front wing to reach critical stall angle before the rear wing resulting in desirable stall behavior. Overall this method of stall behavior modification reduces overall efficiency due to induced drag increases caused by the differential of angle of attack between the wings. Therefore the previous methods of longitudinal stability modification stated are the preferred method.

[0034] Referring to Figure 3 the design of a J/BW aircraft includes increasing the tow-in angle of the wingtips 7 and 8 to 2.5 degrees to achieve additional Yaw axis stability. This tow in angle can be greater than 2.5 degrees or reduced to zero dependent on the desired stability characteristics required by the aircraft. By increasing the Tow-in angle a differential of wingtip angle of attack is created by which as when relative airflow 9 is arriving at angle other than centerline of aircraft, the wingtip differential of angles relative to airflow 9 yaws the aircraft to self center with respect to the relative airflow 9 and the differential of wingtip angles 7 and 8 respectively.

[0035] Referring to Figure 6 a J/BW aircraft includes determining the outward angle of 10 degrees of the wingtip 10 with regards to the top section of the wingtip in comparison to the lower section of the wingtip to achieve additional Lateral or Roll stability. This angle can vary dependent on the stability required either increasing past 10 degrees or decrease to zero. When the aircraft is turning any side slip airflow 11 is deflected downwards by the wingtip outward angle causing the aircraft to return to level in roll.

[0036] Referring to Figure 7 a method for design of a J/BW aircraft includes determining the dihedral angle 2.5 degrees of the front and or rear wing 12 to achieve additional Lateral or Roll stability. The secondary effect of this is to provide additional ground clearance for the wingtips for takeoff and landing. Dihedral angle can vary upon the desired aircraft requirement and can be added to either or both wings to create additional roll stability. The dihedral on the front wing in particular can be increased to provide roll stability as well as ground clearance for landing gear suited towards large transport aircraft.

[0037] Referring to figure 1 example of Joined/ Box wing aircraft incorporating the first embodiment of a square type of wingtip is to join the wings into a box style of arrangement and is projected to offer pressure interactions post aircraft that interact with each other to create a smaller amount of wake turbulence or induced drag.

[0038] Referring to Figure 8 a method for design of a second embodiment of a Joined/ Box wing aircraft incorporating Radial type of wingtip design where the airfoils of the upper wing 14 and lower wing 15 are blended together through the radial wingtip, incorporating blended airfoil sections around the median point 13 of the radial wingtip section. The Radius of the radial wingtip 16 can be fixed or changing across the radial wingtip length. The radial wingtip is projected to provide additional induced drag savings by reducing abrupt pressure changes around the wing tips and creating a singular initiation point for wingtip vortices between the pair of wings, the post aircraft wake turbulence and suction is blended smoothly and overall wake turbulence or induced drag is projected to be further reduced when compared to the Square type of wingtip.

[0039] A method for design of the first embodiment of the J/BW wing uses rudders at both wingtips to control yaw when applied independently or combined to act as an air break. Referring to Figure 9 a second embodiment of a Joined/ Box wing aircraft incorporating Radial type of wingtip design where the yaw control is achieved through a split multi piece rudder system or contour morphing sections 17. Due to the radial shape of the second embodiment of wingtip a conventional rudder cannot be employed to control yaw. Therefore, a split series of radial panels is extended through a mechanism to actuate them either by individual servo actuators being either electric or hydraulic or through a series of cams and universal joints actuated by a single or lessor number of actuators. This in turn provides dynamic control of airflow and drag at each wingtip to provide yaw control. Actuation of both rudders can be used as an airbrake to slow the aircraft down.

[0040] Referring to Figure 10 The position of the fuselage in relation to the wings can vary between a low mounted position 18 or mid mounted position 19 based on the mission requirements of the design.

[0041] The J/BW designs can also better incorporate low energy density propulsive technologies due to the efficiency gains and additional lift capability when compared to a traditional aircraft. These technologies can include solar panels on wings, electric and hybrid propulsion.

[0042] The general arrangement of the wings can incorporate variations in front wing sweep angle or rear wing sweep angle or even sweep forward dependent on mission requirements such as fuselage size needed in the design and drag curve requirements.

[0043] Additional technologies such as variable pitch propeller system that also provides thrust vectoring abilities, jet propulsion and vertical lift propulsion arrangements can be incorporated into this design.

[0044] While various embodiments have been described above, this disclosure is not intended to be limited thereto. Variations can be made to the disclosed embodiments that are still within the scope of the appended claims.

Claims

WHAT IS CLAIMED:

1. A set of design features to create a working J/BW (Joint/ Box Wing) aircraft
2. The design features for controlling high speed stability of J/BW aircraft through wing area ratio differentials between the front and back wing.
3. The design features for controlling pitch stability of J/BW aircraft through the means of wing camber differentials between the front and back wings.
4. The design features for controlling pitch stability of a J/BW aircraft through independently changing the angle of attack of either or both of the front and rear wings.
5. The design features for controlling yaw of a J/BW aircraft stability through tow in angle of the wing tips.
6. The design features for controlling Roll stability of a Joined/Box Wing aircraft through changing outward angle of the wingtips.
7. The design features for controlling Roll stability of a J/BW aircraft through changing dihedral of the front and rear wings, the front wing giving additional ground clearance to the wingtips for takeoff and landing.
8. The radial wingtip design features for a J/BW aircraft to reduce induced drag of a Joined/ Box Wing aircraft.
9. The method of yaw control encompassing drag rudders on a J/BW aircraft that uses the embodiment of the radial wingtips.
10. The positioning of the fuselage in relation to the Joined/ Box Wing configuration.