# US 2021/0276725 A1 · Systems and Methods for Defining APU Steady State Speed according to the Aircraft Operational Conditions > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0276725 A1 - Document ID: US20210276725A1 - Status: Published application - Kind: A1 - Application number: 17/187,148 - Filed: 2021-02-26 - Published: 2021-09-09 - Earliest claimed: 2020-03-05 - Assignees: Yaborã IndúStria AeronáUtica S.A. - Applicants: Yaborã Indústria Aeronáutica S.A. - Inventors: Maurício Rodrigues LIMA; João Miguel Ferreira CUNHA - Web page: https://patentgrep.com/patent/US20210276725A1 ## CPC - F02C 6/06: providing compressed gas (F02C6/10 takes precedence) - B64D 31/00: Power plant control systems; Arrangement of power plant control systems in aircraft - B64D 31/06: actuated automatically - B64D 41/00: Power installations for auxiliary purposes - B64F 5/60: Testing or inspecting aircraft components or systems - F02C 9/18: by bleeding, bypassing or acting on variable working fluid interconnections between turbines or compressors or their stages {(F02C3/113 takes precedence)} - F05D 2220/50: for auxiliary power units (APU's) - 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 - B64F: GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS ## Abstract A method for defining the steady state speed of an auxiliary power unit (APU) of an aircraft according to the aircraft operating condition. ## Claims ### Claim 1 In an aircraft comprising an auxiliary power unit, a control method comprising performing operations including the following with at least one processor: determining at least one aircraft operating condition; and controlling the steady state speed of the auxiliary power unit based on the at least one aircraft operating condition. ### Claim 2 (depends on 1) The control method of claim 1 wherein the at least one aircraft operating condition comprises aircraft power demand. ### Claim 3 (depends on 1) The control method of claim 1 wherein the at least one aircraft operating condition comprises aircraft weight on wheels. ### Claim 4 (depends on 1) The control method of claim 1 wherein the at least one aircraft operating condition comprises ECS mode. ### Claim 5 (depends on 1) The control method of claim 1 wherein the at least one aircraft operating condition comprises main engine start. ### Claim 6 (depends on 1) The control method of claim 1 wherein the at least one aircraft operating condition comprises aircraft bleed operation mode ### Claim 7 (depends on 1) The control method of claim 1 wherein controlling includes setting the auxiliary power unit steady state speed setpoint to be (i) less than 100% rated speed and (ii) higher than the auxiliary power unit underspeed threshold. ### Claim 8 (depends on 1) The control method of claim 1 wherein when on ground condition and when the auxiliary power unit is providing bleed air to the main engine start, the processor sets the steady state speed setpoint to 100% rated speed of the auxiliary power unit, wherein 100% rated speed is the auxiliary power unit steady state speed that is capable of providing maximum pneumatic and electrical power from the auxiliary power unit. ### Claim 9 (depends on 1) The control method of claim 1 wherein when in flight condition, the processor sets a steady state speed setpoint of the auxiliary power unit to be 100% rated speed, wherein 100% rated speed is the auxiliary power unit steady state speed that is capable of providing maximum pneumatic and electrical power from the auxiliary power unit. ### Claim 10 An aircraft comprising: an auxiliary power unit, and at least one processor operatively coupled to the auxiliary power unit, the at least one processor being configured to perform operations including the following: determining at least one aircraft operating condition; and controlling the steady state speed of the auxiliary power unit based on the at least one aircraft operating condition. ### Claim 11 (depends on 10) The aircraft of claim 10 wherein the at least one aircraft operating condition comprises aircraft power demand. ### Claim 12 (depends on 10) The aircraft of claim 10 wherein the at least one aircraft operating condition comprises aircraft weight on wheels. ### Claim 13 (depends on 10) The aircraft of claim 10 wherein the at least one aircraft operating condition comprises ECS mode. ### Claim 14 (depends on 10) The aircraft of claim 10 wherein the at least one aircraft operating condition comprises main engine start. ### Claim 15 (depends on 10) The aircraft of claim 10 wherein the at least one aircraft operating condition comprises aircraft bleed operation mode ### Claim 16 (depends on 10) The aircraft of claim 10 wherein the processor is configured to set the auxiliary power unit steady state speed setpoint to be (i) less than 100% rated speed and (ii) higher than the auxiliary power unit underspeed threshold. ### Claim 17 (depends on 10) The aircraft of claim 10 wherein when on ground condition and when the auxiliary power unit is providing bleed air to the main engine start, the processor is configured to set the steady state speed setpoint to 100% rated speed of the auxiliary power unit, wherein 100% rated speed is the auxiliary power unit steady state speed that is capable of providing maximum pneumatic and electrical power from the auxiliary power unit. ### Claim 18 (depends on 10) The aircraft of claim 10 wherein when in flight condition, the processor is configured to set a steady state speed setpoint of the auxiliary power unit to be 100% rated speed, wherein 100% rated speed is the auxiliary power unit steady state speed that is capable of providing maximum pneumatic and electrical power from the auxiliary power unit.