# US 11,442,446 B2 · Automatic envelope limiting based on detected hydraulic failures > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,442,446 B2 - Document ID: US11442446B2 - Status: Granted - Kind: B2 - Application number: 15/696,345 - Filed: 2017-09-06 - Published: 2019-03-07 - Granted: 2022-09-13 - Earliest claimed: 2017-09-06 - Assignees: Sikorsky Aircraft Corporation - Applicants: Sikorsky Aircraft Corporation - Inventors: Christopher A. Thornberg; Derek H. Geiger; Joseph T. Driscoll; Ole Wulff - Web page: https://patentgrep.com/patent/US11442446B2 ## CPC - G05D 1/0055: {with safety arrangements} - B64C 13/503: {Fly-by-Wire} - B64C 27/56: characterised by the control initiating means, e.g. manually actuated - B64C 27/57: automatic or condition responsive, e.g. responsive to rotor speed, torque or thrust - B64C 27/64: using fluid pressure, e.g. having fluid power amplification - G05D 1/0858: {specially adapted for vertical take-off of aircraft} - G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES - B64C: AEROPLANES; HELICOPTERS ## Abstract A rotary-wing aircraft and system for flying a rotary-wing aircraft. The aircraft includes a servo system for actuating a rotor of the aircraft. A hydraulic system provides hydraulic power to the servo system, and a sensor measures a parameter of the hydraulic system. A processor determines a condition of the hydraulic system from the parameter and enforces an effective flight envelop based on the condition of the hydraulic system in order to fly the aircraft within the effective flight envelope. ## Claims ### Claim 1 A system for flying a rotary-wing aircraft, comprising: a servo motor for actuating a rotor of the rotary-wing aircraft; a hydraulic system for providing hydraulic power to the servo motor; a sensor that measures a hydraulic parameter of the hydraulic system; a processor configured to: determine an impaired condition of the hydraulic system from the hydraulic parameter, calculate a flight envelope of the aircraft based on a nominal flight envelope for the hydraulic system operating at full capacity and the impaired condition of the hydraulic system, and operate the hydraulic system within the capabilities of the hydraulic system in its impaired condition to fly the aircraft within the flight envelope. ### Claim 2 (depends on 1) The system of claim 1, wherein the hydraulic parameter is a hydraulic pressure in the servo motor and the processor is further configured to calculate the flight envelope based on the hydraulic pressure in the servo motor. ### Claim 3 (depends on 1) The system of claim 1, wherein the processor is further configured to: receive a pilot input requesting operation of the aircraft to fly outside of the flight envelope; and generate a flight command in response to the pilot input to a flight component and hardware of the aircraft to fly the aircraft so that the aircraft is maintained within the flight envelope. ### Claim 4 (depends on 1) The system of claim 1, wherein the processor is further configured to determine the flight envelope by selecting the flight envelope from a database of flight envelopes. ### Claim 5 (depends on 4) The system of claim 4, wherein the processor is further configured to select the flight envelope from the database based on when a value of the hydraulic parameter is within a range corresponding to the flight envelope. ### Claim 6 (depends on 1) The system of claim 1, wherein the processor is further configured to calculate the flight envelope dynamically based on a value of the hydraulic parameter. ### Claim 7 (depends on 2) The system of claim 2, wherein the sensor further measures a load on the servo motor and the processor is further configured to calculate the flight envelope from the hydraulic pressure in the hydraulic system and the load on the servo motor. ### Claim 8 A rotary-wing aircraft, comprising: a servo system for actuating a rotor of the rotary-wing aircraft; a hydraulic system for powering the servo system; a sensor that measures a hydraulic parameter of the hydraulic system; and a processor configured to: determine an impaired condition of the hydraulic system from the hydraulic parameter, calculate a flight envelope of the aircraft based on a nominal flight envelope for the hydraulic system operating at full capacity and the impaired condition of the hydraulic system, and operate the hydraulic system within the capabilities of the hydraulic system in its impaired condition to fly the aircraft within the flight envelope. ### Claim 9 (depends on 8) The rotary-wing aircraft of claim 8, wherein the hydraulic parameter is a hydraulic pressure in the servo motor and the processor is further configured to calculate the flight envelope based on the hydraulic pressure in the servo motor. ### Claim 10 (depends on 8) The rotary-wing aircraft of claim 8, wherein the processor is further configured to: receive a pilot input requesting operation of the aircraft to fly outside of the flight envelope; and generate a flight command in response to the pilot input to a flight component and hardware of the aircraft to fly the aircraft so that the aircraft is maintained within the flight envelope. ### Claim 11 (depends on 8) The rotary-wing aircraft of claim 8, wherein the processor is further configured to determine the flight envelope by selecting the flight envelope from a database of flight envelopes when a value of the parameter is within a range assigned to the flight envelope. ### Claim 12 (depends on 8) The rotary-wing aircraft of claim 8, wherein the processor is configured to calculate the flight envelope dynamically based on a value of the hydraulic parameter. ### Claim 13 (depends on 9) The rotary-wing aircraft of claim 9, wherein the sensor further measures a load on the servo motor and the processor is further configured to calculate the flight envelope from the hydraulic pressure in the hydraulic system and the load on the servo motor. ### Claim 14 (depends on 8) The rotary-wing aircraft of claim 8, wherein the flight envelope is dynamically calculated. ### Claim 15 (depends on 1) The system of claim 1, wherein the flight envelope is dynamically calculated.