Patent Application
20130319003
This application relates to a method and apparatus for providing a fire resistant shielding to a mount for mounting an auxiliary power unit (“APU”) in an aircraft.
APUs are provided in an aircraft, and are utilized as a source of power before the main gas turbine engines are started. An APU includes a gas turbine engine, a generator, and associated systems. The APU is typically mounted in a portion of an aircraft, such as the tail cone, which may be subject to any number of environmental challenges. As an example, there is potential for exposure to flame, and for mechanical stresses.
The APUs have typically been mounted by a plurality of struts attached to brackets at opposed sides of the APU. These struts are mounted to a first structural link that is in turn attached to a mount bracket that is bolted to a gear box of the APU.
It has been challenging to provide a connection between the struts and the gear box that can survive exposure to flame, and withstand the stresses encountered by the mount.
Various flame resistant blankets have been provided in an attempt to protect the connection of the bracket to the gear box. These blankets have been relatively flexible and made of composite materials. However, they are complex, costly, weigh an undesirably large amount, are relatively fragile, and require customer installation as the attachments used have often resulted in separation.
An auxiliary power unit has a gas turbine engine, a generator, and a gear box. A mount bracket is mechanically attached to the gear box. The bracket is for connecting to a plurality of struts. The struts are for connecting to an aircraft housing. A shield box is formed of a flame resistant rigid material. The shield box encloses the mount bracket to provide flame protection to the mechanical attachment.
These and other features may be best understood from the following drawings and specification.
As shown, a gear box 22 receives a mount link 28 which is bolted (30) by a mount bracket 32 to the gear box 22. This attachment secures a plurality of struts 26 which extend to an aircraft housing 27, shown schematically. The struts 26 are attached to the mount link 28 at an area 90 spaced from a point 91 where the link 28 is secured to the bracket 32. As can be seen, a pin 93 extends from bracket 32 to the point 91. As mentioned above, there is potential for the mount bracket 32 to be exposed to flame. The mount must also withstand the mechanical stresses and strains encountered to support the APU 21 on the aircraft housing 27.
In this embodiment, the struts 26 and the mount link 28 are outward of the shielding box 40. As can be seen, a hole 92 in shielding' box 40 allows the pin 93 to extend outwardly. The shielding box 40 protects the underlying mount bracket 32 and its bolts 30.
Also, the shielding box 50 covers and protects a portion of the gearbox 22 near the mount brackets 32. In a fire situation, the gearbox may be engulfed and transfer fire to the mount bracket 32. The shielding box limits this heat transfer by covering the gearbox 22 near the bracket 32.
The fuel lines 50 can be seen to be received in an open space between the ledge 46 and the flange 44.
In addition, the struts 26, and the underlying mount link 28 (not seen in
The shielding boxes are formed of flame resistant rigid material. An appropriate metal, or a fiber composite material may be utilized to form the shielding boxes. Suitable metals may include a stainless steel, Inconel, or titanium, or various alloys of those metals. Potential composite materials may include carbon or fiberglass materials.
Although embodiments of this invention have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
