Aircraft with an auxiliary power unit attached to the aircraft fuselage by means of an attachment system

Abstract

An aircraft with an auxiliary power unit attached to the aircraft fuselage via an attachment system. The auxiliary power unit is placed inside the aircraft fuselage structure. The attachment system comprises a plurality of structural wires that link the auxiliary power unit to the aircraft fuselage structure. An attachment device is located at the end of each structural wire to connect the structural wire to the aircraft fuselage structure. Each attachment device comprises a metallic plate adjacent to the aircraft fuselage structure and a layer of damping elastomeric material adjacent to the metallic plate. The metallic plate is placed between the layer of damping elastomeric material and the aircraft fuselage structure. The attachment device is joined to the aircraft fuselage structure by attachment fasteners.

Claims

1. An aircraft with an auxiliary power unit attached to an aircraft fuselage via an attachment system, the auxiliary power unit being placed inside an aircraft fuselage structure, the attachment system comprising: a plurality of structural wires linking the auxiliary power unit to the aircraft fuselage structure, an attachment device located at the end of each structural wire to connect the structural wire to the aircraft fuselage structure, each attachment device comprising: a metallic plate adjacent to the aircraft fuselage structure, a layer of damping elastomeric material adjacent to the metallic plate, such that the metallic plate is placed between the layer of damping elastomeric material and the aircraft fuselage structure, the attachment device being joined to the aircraft fuselage structure by attachment fasteners, wherein each of the plurality of wires is loaded in tension providing a primary attachment system for the auxiliary power unit.

2. The aircraft according to claim 1, wherein the structural wires are metallic.

3. The aircraft according to claim 2, wherein the structural wires are galvanized.

4. The aircraft according to claim 1, wherein the structural wires comprise several threads around a central metallic or fiber strand.

5. The aircraft according to claim 1, wherein there are 16 structural wires that link the auxiliary power unit to the aircraft fuselage structure.

6. The aircraft according to claim 1, wherein the attachment fasteners comprise bolts that extend across the metallic plate and the layer of damping elastomeric material, the portion of the bolts that crosses the metallic plate and the layer of damping elastomeric material being surrounded by bearings.

7. The aircraft according to claim 1, wherein the auxiliary power unit is attached to the aircraft fuselage in a tailcone of the aircraft fuselage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a more complete understanding of the present invention, it will be described below in greater detail, making reference to the attached drawings, in which:

(2) FIG. 1 is a perspective view of an aircraft of the invention.

(3) FIG. 2 is a view of the rear part of the fuselage of the aircraft of the invention, including its tailcone.

(4) FIG. 3 is a cross-section view of the tailcone of the aircraft, showing an auxiliary power unit.

(5) FIG. 4 is a schematic view of the tailcone of the aircraft and the auxiliary power unit, with an attachment system.

(6) FIG. 5 is a schematic view of an attachment device of the attachment system.

(7) FIG. 6 is a schematic plan view of the attachment device of FIG. 5.

(8) FIG. 7 is a view of the configuration of a structural wire of the attachment system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) FIG. 1 shows an aircraft 1 of the invention with its aircraft fuselage 2, and FIG. 2 shows, more in detail, the rear part 4 of the aircraft 1 of FIG. 1, including the tailcone 3.

(10) FIG. 3 shows the tailcone 3 of the aircraft 1 of FIGS. 1 and 2 connected to the rest of the aircraft fuselage 2 structure, with an auxiliary power unit 5 (APU) inside, and FIGS. 3 and 4 show the auxiliary power unit 5 attached to the aircraft fuselage 2 in the tailcone 3 of the fuselage 2.

(11) FIG. 4 shows the attachment system that attaches the auxiliary power unit 5 to the aircraft fuselage 2 in a schematic way. The attachment system comprises a plurality of structural wires 6 that link the auxiliary power unit 5 to the aircraft fuselage 2 structure, as can be seen in FIG. 4. The system also comprises an attachment device 7 (represented in detail in FIGS. 5 and 6) located at the end of each structural wire to connect the structural wire to the aircraft fuselage 2 structure. Each attachment device 7 of FIGS. 5 and 6 comprises:

(12) a metallic plate 8 adjacent to the aircraft fuselage 2 structure,

(13) a layer 9 of damping elastomeric material adjacent to the metallic plate 8, such that the metallic plate 8 is placed between the layer 9 of damping elastomeric material and the aircraft fuselage 2 structure.

(14) FIGS. 5 and 6 also show that the attachment device 7 is joined to the aircraft fuselage 2 structure by an attachment fastener 10.

(15) The attachment system that attaches the wires 6 to the aircraft fuselage 2 structure must be able to absorb the vibrations transmitted from the APU to the fuselage 2 structure due to the operation of the engine or by inertial displacements of the machine.

(16) As for the structural wires 6 that link the auxiliary power unit 5 to the aircraft fuselage 2 structure, they can be metallic wires, which are the most common ones that can be found in the market.

(17) The structural wires 6 of the system can be built as a helicoidal twister composed by several threads 11 around a central metallic or fiber strand 12 (see FIG. 7).

(18) For assembly installation purposes, a longitudinal stripe could be painted along the entire length of the strand or wire rope while it is under the prescribed measuring tension. Striping allows structural strand or wire rope assemblies to be installed in the proper orientation. If the stripe is straight after an assembly is erected, its length, when loaded to the measuring tension, will be the same as measured during fabrication.

(19) Galvanized (zinc-coated) wire is usually used in rope/strand to combat the corrosive environments of salt water, atmospheric contaminants, and humid and moist conditions. The combination of strand and wire rope physical properties and zinc coating has been successfully used in many applications.

(20) Attaching sockets correctly is of prime importance because the connection must be as strong as the strand or wire rope. But also, the attachment must be able to absorb the vibrations transmitted from the APU to the structure due to the operation of the engine or by inertial displacements of the machine.

(21) Current suspension systems are composed by eight metallic struts and four isolators to damp the transmission from APU loads to the structure. The weight of these systems is around 15 Kg.

(22) An equivalent design concept based on wires 6 can be composed by 16 wires 6 of inch diameter and around an average length of 1 meter (3 ft).

(23) In this way, the total weight of the wires 6 would be around=16*3*0.24=11.52 lb=5.184 Kg. Adding the sockets weight, the total weight of the new system concept could be around 10 Kg, so there is an important weight reduction.

(24) According to an embodiment of the invention, there are 16 structural wires 6 that link the auxiliary power unit 5 to the aircraft fuselage 2 structure,

(25) As for the attachment fasteners 10 that join the attachment device 7 to the aircraft fuselage 2 structure, they may comprise bolts that extend across the metallic plate 8 and the layer 9 of damping elastomeric material. As shown in FIG. 5, the portion of the bolts that crosses the metallic plate 8 and the layer 9 of damping elastomeric material is surrounded by bearings 13 in the represented embodiment.

(26) Although the present invention has been fully described in connection with preferred embodiments, it is evident that modifications may be introduced within the scope thereof, not considering this as limited by these embodiments, but by the contents of the following claims.

(27) While at least one exemplary embodiment of the present invention(s) 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.