# US 12,179,934 B2 · Method and apparatus for auxiliary power unit installation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,179,934 B2 - Document ID: US12179934B2 - Status: Granted - Kind: B2 - Application number: 16/404,559 - Filed: 2019-05-06 - Published: 2020-11-12 - Granted: 2024-12-31 - Earliest claimed: 2019-05-06 - Assignees: The Boeing Company - Applicants: The Boeing Company - Inventors: Alan J. Wong; Curtis John Call; Theodore Carl Arnold - Web page: https://patentgrep.com/patent/US12179934B2 ## CPC - B64D 41/00: Power installations for auxiliary purposes - B64C 1/16: specially adapted for mounting power plant - B64D 27/402: {comprising box like supporting frames, e.g. pylons or arrangements for embracing the power plant} - B64D 2041/002: {Mounting arrangements for auxiliary power units (APU's)} - B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT - B64C: AEROPLANES; HELICOPTERS ## Abstract An aircraft is disclosed, including a fuselage having a compartment configured to house refueling apparatus. An auxiliary power unit is mounted in the compartment. ## Claims ### Claim 1 An aircraft, comprising: a fuselage including a pressurized internal volume and a refueling apparatus compartment, a tail-mounted first Auxiliary Power Unit (APU), and a second APU mounted in the refueling apparatus compartment, wherein: the refueling apparatus compartment is disposed in the pressurized internal volume and sealed off from the pressurized internal volume, the refueling apparatus compartment is disposed forward of the first APU, the refueling apparatus compartment includes: a main body portion having multiple walls reinforced with reinforcing ribs to improve structural strength needed to withstand expected pressure differentials between the pressurized internal volume and the atmosphere, the multiple reinforced walls being distinct from an aircraft skin, and an aft tapered portion connected to the main body portion and generally forming a hose trough that extends aft to an aperture in a skin of an underside of the fuselage, the aperture being disposed forward of the first APU, and an exhaust duct of the second APU extends through the hose trough to the aperture. ### Claim 2 (depends on 1) The aircraft of claim 1, wherein the refueling apparatus compartment maintains an air pressure substantially equal to the air pressure external to the fuselage. ### Claim 3 (depends on 1) The aircraft of claim 1, wherein the refueling apparatus compartment has a hose reel chamber connected to the hose trough, the hose reel chamber being larger than the hose trough, the hose reel chamber and the hose trough each including a plurality of reinforced planar wall sections. ### Claim 4 (depends on 1) The aircraft of claim 1, wherein the APU is connected to a supply pipe of a probe and drogue refueling system of the aircraft. ### Claim 5 (depends on 1) The aircraft of claim 1, wherein: the refueling apparatus compartment is defined between the multiple walls reinforced with reinforcing ribs and a skin of the fuselage. ### Claim 6 An aircraft, comprising: a pressurized fuselage, an un-pressurized internal compartment disposed in the fuselage, and an APU mounted in the compartment, wherein: the internal compartment is defined between a plurality of reinforced planar wall sections and a skin of the fuselage, and the reinforced planar wall sections include a plurality of reinforcing ribs to improve structural strength needed to withstand expected pressure differentials between the pressurized fuselage and the atmosphere, the plurality of reinforced planar wall sections being distinct from the skin of the fuselage, and the internal compartment includes a main body portion and an aft tapered portion. ### Claim 7 (depends on 6) The aircraft of claim 6, wherein the internal compartment is disposed at an underside of the fuselage. ### Claim 8 (depends on 6) The aircraft of claim 6, wherein the plurality of reinforced planar wall sections form the main body portion and the tapered portion, with the tapered portion extending aft from the main body portion. ### Claim 9 (depends on 6) The aircraft of claim 6, wherein the fuselage has a tail cone and the internal compartment is disposed forward of the tail cone. ### Claim 10 (depends on 6) The aircraft of claim 6, wherein the APU is suspended from an upper one of the plurality of reinforced planar wall sections of the internal compartment. ### Claim 11 (depends on 6) The aircraft of claim 6, wherein the plurality of reinforcing ribs include ribs extending perpendicular to the centerline of the aircraft, and ribs extending parallel to the centerline of the aircraft, at least one rib extending perpendicular to the skin of the fuselage. ### Claim 12 (depends on 6) The aircraft of claim 6, wherein the plurality of reinforced planar wall sections include an electrical access point to allow electrical connection of the APU to an electric grid of the aircraft, and to maintain the pressure of the compartment. ### Claim 13 (depends on 6) The aircraft of claim 6, wherein at least two of the plurality of reinforced planar wall sections are parallel a centerline of the aircraft, and are mutually perpendicular. ### Claim 14 (depends on 6) The aircraft of claim 6, wherein the main body portion is rectangular in cross-section as taken perpendicular to a centerline of the aircraft. ### Claim 15 (depends on 14) The aircraft of claim 14, wherein an engine of the APU is mounted in the main body portion and an exhaust duct of the APU is mounted in the tapered portion. ### Claim 16 (depends on 6) The aircraft of claim 6, wherein an exhaust duct of the APU is contained within the compartment. ### Claim 17 An aircraft, comprising: a fuselage having a skin and an underside, a compartment in a pressurized internal volume of the fuselage, defined between a plurality of reinforced walls and the skin of the fuselage at the underside of the fuselage, the reinforced walls being reinforced with reinforcing ribs to maintain substantially the same pressure as the pressure external to the aircraft, the plurality of reinforced walls being distinct from the skin of the fuselage, a first aperture through the underside of the fuselage, into the compartment, a second aperture through the underside of the fuselage, into the compartment, the second aperture being aft of the first aperture, and an APU mounted in the compartment, having an air intake extending through the first aperture and an exhaust extending to the second aperture, wherein the first aperture and the second aperture are each forward of a tail cone of the aircraft. ### Claim 18 (depends on 17) The aircraft of claim 17, wherein the first aperture is through an external service access door, the air intake of the APU extending through the external service access door. ### Claim 19 (depends on 18) The aircraft of claim 18, wherein the air intake of the APU includes an inlet structure mounted to the access door, external to the fuselage. ### Claim 20 (depends on 17) The aircraft of claim 17, further including a tail-mounted APU.