# US 12,110,121 B2 · 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 12,110,121 B2 - Document ID: US12110121B2 - Status: Granted - Kind: B2 - Application number: 17/187,148 - Filed: 2021-02-26 - Published: 2021-09-09 - Granted: 2024-10-08 - 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/US12110121B2 ## 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 a constant speed auxiliary power unit having a rated speed, a control method performing operations including the following with at least one processor: determining an aircraft operational mode, wherein the determined aircraft operational mode indicates at least an aircraft ground operation mode, an aircraft flight operation mode and an aircraft main engine start operation mode; selecting a constant steady state speed setpoint of the auxiliary power unit that corresponds to the determined aircraft operational mode, wherein the selected constant steady state speed setpoint of the auxiliary power unit is fixed for the determined aircraft operational mode and is not impacted by factors other than the determined aircraft operational mode, thereby adapting the selected constant steady state speed setpoint of the auxiliary power unit to the determined aircraft operational mode; and controlling the auxiliary power unit to operate at the selected constant steady state speed setpoint. ### Claim 2 (depends on 1) The control method of claim 1 wherein the determined aircraft operational mode is responsive to a weight on wheels. ### Claim 3 (depends on 1) The control method of claim 1 wherein the aircraft operational mode further indicates a combination of an environmental control system (ECS) air-conditioning ON/OFF mode, and main engine operation. ### Claim 4 (depends on 1) The control method of claim 1 wherein the aircraft operational mode further indicates aircraft bleed operation. ### Claim 5 (depends on 1) The control method of claim 1 wherein the controlling the auxiliary power unit includes setting the constant steady state speed setpoint of the auxiliary power unit to be (i) less than 100% of the rated speed and (ii) higher than an auxiliary power unit underspeed threshold. ### Claim 6 (depends on 1) The control method of claim 1 further including when the aircraft operational mode comprises the aircraft ground operation mode and when B the auxiliary power unit is providing bleed air to start a main engine, the at least one processor setting the selected constant steady slate speed setpoint of the auxiliary power unit to 100% rated speed of the auxiliary power unit, wherein the 100% rated speed is a steady state speed of the auxiliary power unit that is capable of providing maximum pneumatic and electrical power from the auxiliary power unit. ### Claim 7 (depends on 1) The control method of claim 1 further including when the aircraft operational mode is the aircraft flight operation mode, the at least one processor setting the constant steady state speed setpoint of the auxiliary power unit to be 100% rated speed, wherein the 100% rated speed is a steady state speed of the auxiliary power unit for providing maximum pneumatic and electrical power. ### Claim 8 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 an aircraft operational mode, wherein the determined aircraft operational mode indicates at least an aircraft ground operation mode, an aircraft flight operation mode and an aircraft main engine start operation mode; selecting a constant steady state speed setpoint of the auxiliary power unit that corresponds to the determined aircraft operational condition mode, wherein the selected constant steady state speed setpoint of the auxiliary power unit is fixed for the determined aircraft operational mode and is not impacted by factors other than the determined aircraft operational mode, thereby adapting the selected constant steady state speed of the auxiliary power unit to the determined aircraft operational mode; and B controlling the auxiliary power unit to operate at the selected constant steady state speed setpoint. ### Claim 9 (depends on 8) The aircraft of claim 8 wherein the aircraft operational mode further indicates the aircraft ground operation mode with electrical power only, the aircraft ground operation mode with pneumatic power only, or the aircraft ground operation mode with pneumatic/electrical power. ### Claim 10 (depends on 8) The aircraft of claim 8 wherein the determined aircraft operational mode is responsive to a weight on wheels. ### Claim 11 (depends on 8) The aircraft of claim 8 wherein the determined aircraft operational mode indicates a combination of an environmental control system (ECS) air-conditioning ON/OFF mode, and main engine operation. ### Claim 12 (depends on 8) The aircraft of claim 8 wherein the determined aircraft operational mode further indicates aircraft bleed operation. ### Claim 13 (depends on 8) The aircraft of claim 8 wherein the at least one processor is configured to set the selected constant steady state speed setpoint of the auxiliary power unit to be (i) less than 100% of a rated speed of the auxiliary power unit and (ii) higher than an auxiliary power unit underspeed threshold. ### Claim 14 (depends on 8) The aircraft of claim 8 wherein the at least one processor is configured to set the selected constant steady state setpoint of the auxiliary power unit, when the determined aircraft operational mode comprises the aircraft ground operation mode and when the auxiliary power unit is providing bleed air to start a main engine, to 100% rated speed of the auxiliary power unit, wherein the 100% rated speed is an auxiliary power unit steady state speed that is capable of providing maximum pneumatic and electrical power from the auxiliary power unit. ### Claim 15 (depends on 8) The aircraft of claim 8 wherein the at least one processor is configured to set the constant steady state speed setpoint of the auxiliary power unit when the aircraft operational mode comprises the aircraft flight operation mode, to be 100% rated B speed, wherein the 100% rated speed is an auxiliary power unit steady state speed that is capable of providing maximum pneumatic and electrical power from the auxiliary power unit.