# US 7,461,814 B2 · Dual action inlet door and method for use thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,461,814 B2 - Document ID: US7461814B2 - Status: Granted - Kind: B2 - Application number: 11/299,147 - Filed: 2005-12-08 - Published: 2006-05-18 - Granted: 2008-12-09 - Earliest claimed: 2003-07-22 - Assignees: Honeywell International Inc. - Inventors: Jeffrey M. Hein; Nicholas A. Williams; Yogendra Y. Sheoran; Cecilia S. Lam; Ora Morency Cowans; Benjamen Kurt Higuera; Andrew Stephen Peduchi; Ravisha Pramod Sellahewa; Daniel Brown - Web page: https://patentgrep.com/patent/US7461814B2 ## CPC - F02C 7/04: Air intakes for gas-turbine plants or jet-propulsion plants - B64D 33/02: of combustion air intakes - B64D 41/00: Power installations for auxiliary purposes - F02C 7/045: having provisions for noise suppression - F02C 7/32: Arrangement, mounting, or driving, of auxiliaries - B64D 2033/0213: {specially adapted for auxiliary power units (APU's)} - B64D 2041/002: {Mounting arrangements for auxiliary power units (APU's)} - F05D 2220/50: for auxiliary power units (APU's) - F05D 2260/96: Preventing, counteracting or reducing vibration or noise - F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00) - B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS ## Abstract An inlet door assembly and method for reducing noise from an auxiliary power unit (APU) contained within an aircraft housing is provided. The inlet assembly includes an inlet duct, an actuator, and a door. The inlet duct is configured to extend from the auxiliary power unit to the aircraft housing and has a sidewall that defines a flow passage through which APU noise propagates. The actuator is disposed at least partially within the inlet duct. The door coupled to the actuator. The actuator is also configured to selectively rotate the door between at least a first position, in which at least a portion of the door deflects APU noise in a first direction, and a second position, in which at least a portion of the door deflects the APU noise in a second direction. ## Claims ### Claim 1 An inlet door assembly for reducing noise from an auxiliary power unit (APU) contained within an aircraft having a forward end and an aft end, the inlet assembly comprising: a duct having a sidewall including a forward wall and an aft wall and defining an inlet port, an outlet port, and a flow passage therebetween through which APU noise propagates; a first door rotationally mounted on the forward wall of the duct and having an inner surface facing the duct flow passage and an outer surface forming an exterior of the aircraft, the first door configured to selectively rotate between at least a first position, in which at least a portion of the inner surface of the first door deflects the APU noise in a first direction toward the aircraft aft end, and a second position, in which at least a portion of the inner surface of the first door deflects the APU noise in a second direction into the duct flow passage; a second door rotationally mounted on the aft wall of the duct proximate the first door and having an inner surface facing the duct flow passage, the second door configured to selectively rotate between at least a third position when the first door is in the first position, the third position in which at least a portion of the inner surface of the second door deflects the APU noise in a first direction toward the duct flow passage, and a fourth position when the first door is in the second position, the fourth position in which at least a portion of the inner surface of the second door deflects the APU noise in a second direction toward the outer surface of the first door; and an actuator coupled to the first and second doors and configured to rotate the first door to at least the first and second positions and to rotate the second door to at least the third and fourth positions. ### Claim 2 (depends on 1) The inlet door assembly of claim 1, wherein at least a portion of the second door is disposed within the inlet duct flow passage while in the third position, and at least a portion of the second door is not disposed within the inlet duct flow passage while in the fourth position. ### Claim 3 (depends on 1) The inlet door assembly of claim 1, further comprising: a link coupled to the actuator, the link having first and second ends each coupled to the first and second doors. ### Claim 4 (depends on 3) The inlet door assembly in claim 3, further comprising: first and second joining rods each having first and second ends, wherein the joining rod first ends are each coupled to the first and second doors, respectively, and the joining rod second ends are each coupled to the link first and second ends, respectively. ### Claim 5 (depends on 3) The inlet door assembly of claim 3, wherein the actuator is coupled to the first joining rod. ### Claim 6 (depends on 1) The inlet door assembly of claim 1, wherein the first door is located forward of the second door. ### Claim 7 (depends on 1) The inlet door assembly of claim 1, wherein: the duct includes a shelf that together with at least a portion of the sidewall of the duct defines a well, the first door is adapted to rotate toward and away from the portion of the sidewall, and the second door is adapted to rotate toward and away from the shelf. ### Claim 8 (depends on 7) The inlet door assembly of claim 7, wherein the first door is shorter in length than the second door.