Modular LRU accessory mounting substrate for auxiliary power unit

A multiple accessory support bracket that mounts a plurality of external accessories for an auxiliary power unit (APU) so that all the external accessories may be mounted to the APU in a single operation.

FIELD OF THE INVENTION

The invention relates to the assembly of a gas turbine engine such as an auxiliary power unit (APU), and more particularly a modularised system of assembling accessories onto an APU.

BACKGROUND OF THE INVENTION

Current APU designs for both commercial and military aeronautical applications have individually mounted external accessory components, such as line replaceable units (LRUs), tubes and electrical harnesses, as well as associated mounting brackets, clamps, isolators and bolts. The assembly of so many components onto the surfaces of the APU is a complex and time-consuming process. The number of assembly steps increases the likelihood of quality problems. Furthermore, the procurement and stocking of such a multitude of individual parts increases stored inventory and therefore increases the cost of the manufactured APU.

SUMMARY OF THE INVENTION

The invention comprises a special multiple accessory support bracket that serves to support and mount many or all of the external accessory components, such as LRUs, tubes and electrical harnesses that connect to the APU to facilitate installation of the components onto the accessory support bracket before installation of the accessory support bracket on the APU. The multiple accessory support bracket preferably has its own vibration isolators that serve to provide all components that are mounted to it. Since all the external accessories then install on to the APU as a single pre-assembled unit, this configuration reduces the number of parts needed for assembly, thereby reducing inventory and cost. A mounting tool may be used to conveniently attach and remove the multiple accessory support bracket with all associated components mounted to it, thereby further reducing assembly time and cost.

In the preferred embodiment, the invention comprises a multiple accessory support bracket that supports a plurality of accessories for an APU, comprising: an accessory mounting surface that form-fits a mating surface on the APU; a plurality of primary bracket attachment points on the multiple accessory support bracket for attaching the multiple accessory support bracket to the mating surface on the APU; and a plurality of secondary bracket attachment points along the accessory mounting surface for mounting the accessories on the accessory support bracket.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a perspective view of an APU multiple accessory support bracket or “super Bracket”2according to one possible embodiment of the invention. The super bracket2preferably has a mounting surface4for mounting APU accessories and an attachment surface5on a side of the super bracket2generally opposite from the mounting surface4with a shape and contour that lets the super bracket2form-fit snugly to a mating surface6of an APU8to which it attaches. The super bracket2preferably attaches to the APU mating surface6by way of primary fasteners10that pass through primary bracket attachment points12on the super bracket2and fasten to APU attachment points14on the APU mating surface6. The fasteners10preferably comprise attachment bolts and the APU attachment points14preferably comprise mating threaded holes for the primary fasteners10, although other attachment methods could be used. The primary bracket attachment points12preferably comprise vibration isolators that conveniently provide vibration isolation for all components mounted to the super bracket2.

The super bracket2permits various externally mounted APU accessories to be pre-assembled to it so that mounting of the super bracket2to the APU8mounts all of external accessories that are pre-assembled to it to be mounted to the APU in one operation. Examples of such external APU accessories that may be mounted to the super bracket2are LRUs, electrical wiring harnesses, fuel tube assemblies and pneumatic tube assemblies.

One type of LRU that commonly mounts to the APU8is a fuel control unit (FCU). A FCU16mounts to the mounting surface4of the super bracket2by way of secondary fasteners18that fasten the FCU16to secondary bracket attachment points20in the mounting surface4. The secondary fasteners18preferably comprise attachment bolts and the secondary bracket attachment points20preferably comprise mating threaded holes for the secondary fasteners18, although other attachment methods could be used. Various fuel tubes for distributing fuel to the APU8also attach to the APU8. A fuel tube assembly22that comprises at least one fuel tube24attaches to the mounting surface4of the super bracket2by way of secondary fasteners18that pass through a fuel tube assembly clamp26and fasten to secondary bracket attachment points22in the mounting surface4. Some fuel tubes24typically connect to the FCU16.

Other types of LRUs that commonly mount to the APU are an exciter and a data memory module (DMM). An exciter28and DMM30also mount to the mounting surface4of the super bracket2by way of secondary fasteners18that fasten the exciter28and DMM30to secondary bracket attachment points20in the mounting surface4. Various electrical wires for APU power and data connections also attach to the APU8. An electrical wiring harness32that comprises at least one electrical wire34attaches to the mounting surface4of the super bracket2by way of secondary fasteners18that pass through a wiring harness clamp36and fasten to secondary bracket attachment points20in the mounting surface4. Some of electrical wires34typically connect to the exciter28and DMM30to provide power and data connections for them.

The APU8generally provides pneumatic power as well as electric power by way of bleed air from an engine compressor or compressed air from an integral pneumatic load compressor within the APU8. The compressed air may also be used for air conditioning purposes. A pneumatic tubing assembly38that comprises at least one pneumatic tube40attaches to the mounting surface4of the super bracket2by way of secondary fasteners18that pass through a pneumatic tube assembly clamp42and fasten to secondary bracket attachment points20in the mounting surface4. Pneumatic tubes40may connect to the engine or load compressor of the APU8to couple compressed air for pneumatic power and air conditioning purposes within the aircraft.

FIG. 2is a side view of the APU8sitting in a vertical build jig44and the super bracket2with all accessories as described above pre-mounted to it held in position by an super bracket installation tool46. The super bracket installation tool46holds the super bracket2in proper position, for example with respect to height and angle orientation, relative to the APU8so that the super bracket2may be rapidly attached to the APU8as described above.

FIG. 3is a perspective view of the APU8with the super bracket2attached to it as described above. After attachment of the super bracket2to the APU8, fuel tubes24, electrical wires34and pneumatic tubes40pre-assembled to the super bracket2may be connected to the APU8as required.

Described above is a multiple accessory support bracket that mounts a plurality of external accessories for an auxiliary power unit (APU) so that all the external accessories may be mounted to the APU in a single operation. It should be understood that this embodiment is only an illustrative implementation of the invention, that the various parts and arrangement thereof may be changed or substituted, and that the invention is only limited by the scope of the attached claims.