Aircraft antenna

Abstract

An aircraft antenna (101) including a radome (102) wherein the radome (102) has a main body (105) shaped to enclose one or more antennae (107) when the antenna (101) is attached to a fuselage skin portion (103), wherein the main body (105) includes a front surface portion (203), a rear surface portion (401), adjacent side surface portions (205,207), and an upper surface portion (209) that form a smooth outer aerodynamic surface (211) of the antenna (101), and wherein the upper surface (209) is substantially planar in shape along a length of 60% to 80% of a length (L) of the of the radome (102).

Claims

1. An aircraft antenna including a radome, wherein the radome comprises: a main body shaped to enclose one or more antennae when the aircraft antenna is attached to a fuselage skin portion, wherein the main body comprises a front surface portion, a rear surface portion, adjacent side surface portions, and an upper surface portion that form a smooth outer aerodynamic surface, and wherein the upper surface includes a planar portion that is planar in shape and the planar portion has a length that is in a range of 60% to 80% of a maximum length of the radome.

2. The aircraft antenna of claim 1, wherein the front surface portion forms a first slope angle relative to a first portion of the fuselage skin adjacent the front surface portion and the rear surface portion forms a second slope angle relative to a second portion of the fuselage skin adjacent the rear surface portion, and wherein a magnitude of the first slope angle is greater than a magnitude of second slope angle.

3. The aircraft antenna of claim 2, wherein the magnitude of the first slope angle is in a range of 30 to 40 degrees.

4. The aircraft antenna according to claim 3, wherein the length of the planar portion of the upper surface in a range of 70% to 75% of the maximum length of the radome.

5. The aircraft antenna of claim 2, wherein the magnitude of the second slope angle is in a range of 10 to 20 degrees.

6. The aircraft antenna according to claim 1, whereby the width of the planar portion of the upper surface is in a range of 1% to 80% of a width of the radome.

7. The aircraft antenna according to claim 1, wherein the planar portion of the upper surface is has a height along the length of the planar portion that is approximately 3% of the maximum length of the radome.

8. The aircraft antenna according to claim 1, wherein the planar portion is inclined substantially in a freestream direction.

9. The aircraft antenna according to claim 1, wherein a width of the main body at an aft portion of the main body is less than a width of the main body in a forward portion of the radome.

10. The aircraft antenna according to claim 1, wherein the radome is configured to be attached to the aircraft fuselage by fittings.

11. The aircraft antenna according to claim 1, further comprising an adapter plate wherein the radome is configured to attach to the adapter plate, and the adapter plate is configured to be attached to the aircraft fuselage by fitting.

12. The aircraft antenna according to claim 1, configured to be attached by fittings conforming to an ARINC 791 standard or an ARINC 792 standard.

13. The aircraft antenna according to claim 1, further comprising one or more antennae enclosed by the aircraft antenna radome, wherein the one or more antennae are flat electronically steered antenna.

14. An aircraft fuselage comprising the aircraft antenna according to claim 13.

15. An aircraft comprising the aircraft antenna according to claim 1.

16. An aircraft comprising: a fuselage having an outer skin surface and a longitudinal axis; an antenna mounted to the fuselage at the outer skin surface; and a radome including: a main body covering the antenna, wherein the main body includes a front surface portion, a rear surface portion, and adjacent side surface portions each extending to the outer skin surface and to an upper surface portion, wherein the front surface portion, the rear surface portion the adjacent side portions and the upper surface portion form a smooth outer aerodynamic surface, wherein the upper surface includes a planar portion which is planar along the longitudinal axis and the planar portion has a length along the longitudinal axis in a range of 60% to 80% of the maximum length of the radome.

17. The aircraft according to claim 16, wherein the front surface portion forms a first slope angle relative to a first portion of the fuselage skin which is adjacent and aligned with the front surface along a longitudinal axis of the fuselage, wherein the rear surface portion forms a second slope angle relative to a second portion of the fuselage skin adjacent and aligned with the rear surface portion along the longitudinal axis, and wherein a magnitude of the first slope angle is greater than a magnitude of second slope angle.

18. The aircraft according to claim 17, wherein the magnitude of the first slope angle is in a range of 30 to 40 degrees and the magnitude of the second slope angle is in a range of 10 to 20 degrees.

19. The aircraft according to claim 16, wherein the height of the planar portion is no greater than 3% of the maxim length of the radome.

20. The aircraft according to claim 16, wherein a width of the main body at an aft portion of the main body is less than a width of the main body in a forward portion of the radome.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Embodiments are presented herein are described below with reference to the following drawings, in which:

(2) FIG. 1 is a combined side view and section view of an aircraft antenna (101) comprising a radome (102) and antennae (107) attached to an aircraft fuselage (103) according to the present invention. The section is through the radome in plane XZ.

(3) FIG. 2 is a combined front and section view of the fuselage (103), antenna (101) with the radome (102) of FIG. 1. The section is through the fuselage in plane YZ.

(4) FIG. 3 is a front view of the antenna (101) and radome (102) of FIGS. 1 and 2, showing height H values in plane YZ of the radome (102). The set of sequential geometric points (A through to G) are taken in the YZ plane at peripheral point G of FIG. 4 on the peripheral edge (215) of the radome (1021). Points A to G of FIG. 3 are to be read in conjunction with Table 1.

(5) FIG. 4 is a planform view of the radome (101) of FIGS. 1 to 3 projected onto plane XY, and includes a set of sequential geometric points (A through to M) on the peripheral edge (215) of the radome (101) in the positions shown. Points A to M of FIG. 4 are to be read in conjunction with Table 2.

(6) FIG. 5 is a side view of the antenna (101) and radome (102) of FIGS. 1 to 4 projected onto plane XZ, and including a set of sequential geometric points (A through to M) that intersect the XZ plane and the outer surface (211) of the radome (102) at the positions shown. Points A to M of FIG. 5 are to be read in conjunction with Table 3.

DETAILED DESCRIPTION

(7) With reference to all figures, in a typical coordinate convention appreciated by the skilled person, the X, Y and Z axes correspond to a set of orthogonal aircraft axes, whereby X is the longitudinal aircraft axis, Y corresponds to the lateral aircraft axis oriented in a spanwise direction of the wing of the aircraft, and the direction Z corresponds to the vertical axis, these three directions being orthogonal to each other, and create a set of three orthogonal planes with respect to each other. It should also be noted that typically the freestream direction S is approximately co-linear with the airplane X axis when the aircraft is in steady and level flight.

(8) FIGS. 1 and 2 show an aircraft antenna (101) comprising a radome (102) attached to an upper outer fuselage skin portion (103) of an aircraft (100). The radome (102) comprises an oblong main body (105) that is substantially symmetric through the XZ plane. The main body (105) of the radome (102) extends outward away from the fuselage skin (103) by a height H measured in the Z direction to form an enclosed volume (109) around flat electronically steered antennae (107) arranged in tandem and proceeding in a series of three rows aft-wards within the radome enclosure (109). Other configurations of one or more antennae (107) are also possible.

(9) The main body (105) of the radome (102) is formed from monolithic glass fibre reinforced composite material, however the skilled person will appreciate that any other suitable material such as carbon or quartz reinforced polymer may be used. The material forming the main body (105) may be substantially transparent to radio-frequency (RF) radiation.

(10) Integral stiffeners, ribs or other common components may be used in locations if needed to stiffen the radome (102). The main body (105) comprises a front surface portion (203), a rear surface portion (401), adjacent side surface portions (205, 207) and an upper surface portion (209) that are blended into one another circumferentially such that the main body (105) comprises a symmetric, curved and aerodynamically smooth outer surface (211). The main body (105) has an aerodynamically smooth outer surface substantially free from discontinuations, steps and gaps that may otherwise degrade a laminar boundary layer.

(11) The main body (105) has a total length L measured in the X direction measured on the X-Z axis of symmetry between a leading edge (104) and a trailing edge (106) of the radome (102). The main body (105) of the radome (102) is of width W that is measured in the Y direction, and that may be measured at any point along the length L of the radome (101).

(12) The radome (102) of the present embodiment is attached at an upper outer portion of the fuselage skin (103) upstream from a dorsal fairing (113), which forms a root portion of the leading edge of the vertical tail plane (111). FIG. 2 shows the antenna (101) installation on the aircraft (100). The antenna (101) is upstream of the dorsal fairing (113) and partly obscures it. For reference, an outline (213) of a prior art antenna is provided to compare overall prior art frontal shape and height to the frontal shape and height of the antenna falling within scope of the present invention.

(13) The antennae (107) and the main body (105) are secured to the fuselage (103) via a set of 7 ARINC 791 standard fittings (201) formed of 7 lugs fittings (201) attached to external doublers (not shown) secured to the fuselage skin (103) and bolted to 7 corresponding clevis fittings fitted to the main body (105) and antennae (107). The fittings (201) provide a means of removably attaching the radome (102) to the fuselage portion (103) (meaning the antenna radome is detachable, attachable).

(14) The antenna (101) may also comprise an adapter plate used as a platform to attach the radome (102) and antennae (107) to the fuselage skin (103) using an ARINC 791 or 792 standard set of attachment fittings. In such a case, an aerodynamic skirt component (not shown) may also be used, but it should be appreciated that the outer surface (211) of the antenna (101) would comprise both the radome (102) and the skirt (not shown) and would be considered together to form the uniform outer surface (211) of the antenna (101).

(15) With reference to FIG. 3 the height H of the radome (102) is indicated at a number of indicated set of point stations (A to G), each lying on the outer surface (211) of the radome (102) and as measured from the top most point of the fuselage (103) is given by the following table 1, where H is expressed in terms as a percentage of the Total length L of the radome (102) and the corresponding relative position of the station in the Y direction from a plane of symmetry XZ is expressed as a percentage of the total width W of the radome (102).

(16) TABLE-US-00001 TABLE 1 read in conjunction with FIG. 3 STATION Position in +Y Height H in +Z REF. direction (as % of W) direction (as % of L) A 50% (on plane XZ) 3% B 60% 3% C 69% 3% D 79% 3% E 88% 3% F 96% 1% G 100% ()2%.sup.

(17) As can be seen from Table 1, the height H of the substantially planar upper surface (109) to the fuselage skin (103) is approximately 3% of the overall length L of the radome (102) at the position they are taken. The height is constant across 76% of the width W of the radome at the station also, which is optimised for the type of the antennae (107) enclosed as previously described.

(18) With reference to FIG. 4, the width W of the radome (102) is given at a number of indicated point stations (A to M), each lying on the outer surface (211) of the radome (102) by the following table 2, where W is expressed as a percentage of the total length L of the radome (102) and the corresponding relative position of the station in the X direction from the foremost station is also expressed as a percentage of the total length L of the radome (102).

(19) TABLE-US-00002 TABLE 2 read in conjunction with FIG. 4 STATION Position in +X Width W in +Y REF. direction (as % of L) Direction (as % of L) A 0% 0% B 9% 20% C 18% 31% D 27% 35% E 36% 36% F 45% 36% G 48% 36% H 55% 36% I 64% 35% J 73% 32% K 82% 28% L 91% 18% M 100% 0%

(20) As can be seen from Table 2, the width W of the main body (105) of the radome (102) tapers and in the aft-most 30% of the radome the width W is less than the width W of the main body in the foremost 30% of the radome, in other words; from a planform view the radome is tapered more at the rear portion (401) than the front portion (203) of the radome (102). As can be seen when reading table 1 and 2 in combination, the upper surface (209) is be substantially planar in the Y direction up to 80% i.e. between 1% to 80% of a width W of the radome (102) and along 70% to 75% of the length L of the radome (102), although this width characteristic may extend further between 60 and 80% of the Length L of the radome (102), but performance will be less optimised. Use of such sub ranges provides gradual tapering of the planar surface in the X direction, allowing for a reduction in form drag, and an optimum balance for overall drag reduction of the radome versus the enclosed usable volume available in the X and Y direction for the antenna (107) installation. In terms of aerodynamic performance, this geometry also promotes laminarity of the airflow being maintained over substantially the whole length of the radome (102).

(21) With reference to FIG. 5, the height H of the antenna radome (102) when measured from the topmost point of the fuselage (103) to outer surface (211), is provided in the following table 3 for a number of point stations (A to M) as indicated. Each point station lies on the outer surface (211) of the radome (102). H is expressed in terms as a percentage of the Total length L of the radome (102) when measured in the ZX plane. The position of the point station is and the corresponding relative position of the station in the X direction from a plane of symmetry XZ is expressed as a percentage of the total length L of the radome (102).

(22) TABLE-US-00003 TABLE 3 read in conjunction with FIG. 5 STATION Position in +X height H in +Z REF. direction (as % of L) direction (as % of L) A 0% 0% B 9% 3% C 18% 3% D 27% 3% E 36% 3% F 45% 3% G 48% 3% H 55% 3% I 64% 3% J 73% 3% K 82% 3% L 91% 2% M 100% 0%

(23) As can be understood from FIG. 5 and Table 3, the height of the radome (102) is constant over approximately 74% of the total length L of the radome (101), and the upper surface (209) is co-linear with the freestream direction S (substantially parallel to the X axis).

(24) The front surface portion (203) and a rear surface portion (401) of the radome (102) each form a slope angle (M1, M2, respectively), as shown, relative to the fuselage skin portion when the radome (102) is attached to the fuselage (103). The magnitude of the slope angle M1 is greater than the magnitude of slope angle M2, where M1 is 35 degrees and M2 is 15 degrees.

(25) Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents; then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

(26) While at least one exemplary embodiment is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.