# US 11,897,604 B2 · Rotorcraft with interchangeable rotor diameters > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,897,604 B2 - Document ID: US11897604B2 - Status: Granted - Kind: B2 - Application number: 18/216,068 - Filed: 2023-06-29 - Published: 2024-01-11 - Granted: 2024-02-13 - Earliest claimed: 2021-02-11 - Assignees: Karem Aircraft, Inc. - Applicants: Karem Aircraft, Inc. - Inventors: Abraham Karem; John Paul Parcell - Web page: https://patentgrep.com/patent/US11897604B2 ## CPC - B64C 29/0033: {the propellers being tiltable relative to the fuselage} - B64C 1/063: {Folding or collapsing to reduce overall dimensions, e.g. foldable tail booms} - B64C 3/56: Folding or collapsing to reduce overall dimensions of aircraft - B64C 5/06: Fins (B64C5/08 takes precedence) - B64C 5/12: for retraction against or within fuselage or nacelle - B64C 11/28: Collapsible or foldable blades - B64C 27/463: {Blade tips} - B64D 35/00: Transmitting power from power plants to propellers or rotors; Arrangements of transmissions - B64F 5/00: Designing, manufacturing, assembling, cleaning, maintaining or repairing aircraft, not otherwise provided for; Handling, transporting, testing or inspecting aircraft components, not otherwise provided for - B64C 2211/00: Modular constructions of airplanes or helicopters - B64C: AEROPLANES; HELICOPTERS - 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 ## Abstract A tiltrotor aircraft is designed to accommodate rotors of different diameters, as well as corresponding wings and fuselages with different span and length, while maintaining very high parts commonality, especially with respect to drive train and power source. This enables design and operation of a fleet of such aircraft with significantly different rotor diameters, which are nevertheless optimized for different missions. In preferred embodiments the rotors are configured to have high stiffness and low weight to reduce aero-structural dynamic issues across the fleet. Also in preferred embodiments drive systems are designed for a full range of speed, torque, and power associated with all intended rotors. Turboshaft engine speeds are restricted to a narrow RPM range, so that a single gearset can be replaced to achieve the desired rotor RPM. Also in preferred embodiments, aircraft in a fleet can differ in folded length, empty weight, payload length by up 50%. ## Claims ### Claim 1 A fleet of aircraft, comprising: a first tiltrotor aircraft having a first rotor with rotor diameter of between 12 and 80 feet inclusive, inboard wing span between 21 and 185 feet inclusive, and fuselage length between 20 and 100 feet inclusive; a second tiltrotor aircraft having a second rotor with rotor diameter of between 12 and 80 feet inclusive, inboard wing span between 21 and 185 feet inclusive, and fuselage length between 20 and 100 feet inclusive; wherein the rotor diameter of the second rotor is at least 10% larger than the rotor diameter of the first rotor; wherein each of the first and second rotors has multiple blades, and a radius measured from a center of rotor rotation, and wherein at 10% of the rotor radius, the flap stiffness of the blades in lbs-in2 is not less than 25 times the diameter of the rotor in feet to the fourth power; and wherein the only parts difference in power source and drivetrain components between the first and the second aircraft is different gearsets. ### Claim 2 (depends on 1) The fleet of claim 1, wherein a smallest and largest folded length dimension of the first and second aircraft differ by between 15% and 50% of the first aircraft, inclusive. ### Claim 3 (depends on 1) The fleet of claim 1, wherein a smallest and largest manufacturers empty weight of the first and second aircraft differ by between 15% and 50% of the first aircraft, inclusive. ### Claim 4 (depends on 1) The fleet of claim 1, wherein a smallest and largest payload length dimension of the first and second aircraft differ by between 15% and 50% of the first aircraft, inclusive. ### Claim 5 (depends on 1) The fleet of claim 1, wherein the only significant parts difference in power source and drivetrain components between the first and second aircraft is a single gearset. ### Claim 6 (depends on 1) The fleet of claim 1, wherein at 10% of the rotor radius of each of the first and second rotors, the flap stiffness of each of the blades of each of the first and second rotors in lbs-in2 is not less than 10 times the diameter of the rotor in feet to the fourth power. ### Claim 7 (depends on 1) The fleet of claim 1, wherein for each of the first and second rotors, a total weight of each blade in lbs. does not exceed 0.0015 times the diameter of the rotor in feet cubed. ### Claim 8 (depends on 1) The fleet of claim 1, wherein the rotor diameter of the second rotor is at least 20% larger than the rotor diameter of the first rotor.