# US 12,595,051 B2 · Systems and methods for retracting lift propeller in eVTOL aircraft > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,595,051 B2 - Document ID: US12595051B2 - Status: Granted - Kind: B2 - Application number: 18/477,220 - Filed: 2023-09-28 - Published: 2025-02-06 - Granted: 2026-04-07 - Earliest claimed: 2023-05-26 - Assignees: Archer Aviation Inc. - Applicants: Archer Aviation Inc. - Inventors: Kerry Manning; Nathan Storrs; Scott Graves - Web page: https://patentgrep.com/patent/US12595051B2 ## CPC - B64C 29/0025: {the propellers being fixed relative to the fuselage} - B64C 29/0033: {the propellers being tiltable relative to the fuselage} - B64C 11/02: Hub construction - B64C 27/30: with provision for reducing drag of inoperative rotor - B64C 27/32: Rotors - B64D 27/24: using steam or spring force (jet aircraft B64D27/16) - B64D 27/30: Aircraft characterised by electric power plants - B64D 27/40: Arrangements for mounting power plants in aircraft - B64D 33/08: of power plant cooling systems - B64U 30/293: Foldable or collapsible rotors or rotor supports - 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 - B64U: UNMANNED AERIAL VEHICLES [UAV]; EQUIPMENT THEREFOR ## Abstract A VTOL aircraft includes a lift propeller configured to provide lift during takeoff, landing and hover operations. The lift propeller is configured to be stowed close to a boom surface when not in use during, e.g., cruise flight, to minimize drag around propeller surfaces. The lift propeller may be displaced vertically with respect to the boom when switching to a lift configuration to provide greater separation from the boom to improve lift efficiency and reduce unwanted vibrations. The lift propeller may have a fail-safe configuration that allows the propeller to move passively between lift and stowed configurations, and to fully rotate even when fully retracted. ## Claims ### Claim 1 A vertical takeoff and landing (VTOL) aircraft lift apparatus, comprising: a lift propeller; a motor assembly configured to rotate the lift propeller to generate a lifting force; a support structure configured to support the motor assembly and the lift propeller; and a shaft configured to couple the motor assembly to the lift propeller, the shaft comprising a linear translation section configured to allow linear translation of the lift propeller while transmitting torque to the lift propeller, wherein the shaft is configured to slide vertically through the motor assembly to displace the lift propeller vertically between a lift configuration and a stowed configuration, the lift propeller being vertically displaced between the lift configuration and the stowed configuration, the lift propeller being vertically displaced further from the support structure in the lift configuration than in the stowed configuration. ### Claim 2 (depends on 1) The lift apparatus of claim 1, further comprising: a passive displacement device configured to displace the lift propeller and the shaft into the stowed configuration by applying a passive force. ### Claim 3 (depends on 2) The lift apparatus of claim 2, wherein the passive displacement device is located below the motor assembly. ### Claim 4 (depends on 2) The lift apparatus of claim 2, further comprising: a thrust bearing located between the passive displacement device and the motor assembly. ### Claim 5 (depends on 1) The lift apparatus of claim 1, wherein the lift propeller and the shaft are configured to be passively displaced from the stowed configuration to the lift configuration by the lifting force. ### Claim 6 (depends on 1) The lift apparatus of claim 1, further comprising: an actuator configured to actively displace the lift propeller and the shaft between the lift configuration and the stowed configuration. ### Claim 7 (depends on 1) The lift apparatus of claim 1, wherein the linear translation section comprises a splined section. ### Claim 8 (depends on 1) The lift apparatus of claim 1, further comprising: a damper configured to dampen vibrations as the lift propeller enters at least one of the lift configuration and the stowed configuration. ### Claim 9 (depends on 1) The lift apparatus of claim 1, wherein the lift propeller is configured to make a full rotation in the stowed configuration. ### Claim 10 (depends on 1) The lift apparatus of claim 1, further comprising: a sensor configured to sense that the lift propeller is in one of the lift configuration or the stowed configuration. ### Claim 11 (depends on 1) The lift apparatus of claim 1, further comprising: a shield surface; the lift propeller is located at an aft side of the shield surface; and at least part of the lift propeller is configured to be displaced above a level of the shield surface in the lift configuration and below the level of the shield surface in the stowed configuration. ### Claim 12 (depends on 11) The lift apparatus of claim 11, wherein the part of the lift propeller comprises a tip of a propeller blade or a portion of a hub of the lift propeller. ### Claim 13 (depends on 1) The lift apparatus of claim 1, wherein the support structure comprises a boom. ### Claim 14 (depends on 1) The lift apparatus of claim 1, wherein the motor assembly comprises a bearing seal around the shaft. ### Claim 15 (depends on 14) The lift apparatus of claim 14, wherein the bearing seal comprises a spline nut. ### Claim 16 (depends on 1) The lift apparatus of claim 1, wherein a portion of the lift propeller is inside the support structure in the stowed configuration and outside the support structure in the lift configuration. ### Claim 17 (depends on 1) The lift apparatus of claim 1, wherein the lift propeller is displaced by at least 3 inches. ### Claim 18 (depends on 1) The lift apparatus of claim 1, wherein a gap between a part of the lift propeller and the support structure in the lift configuration is at least 3 times larger than the gap between the part of the lift propeller and the support structure in the stowed configuration. ### Claim 19 (depends on 1) The lift apparatus of claim 1, wherein the lift propeller is displaced by at least 5% of a propeller radius of the lift propeller between the lift configuration and the stowed configuration. ### Claim 20 A method of operating a vertical takeoff and landing (VTOL) aircraft lift apparatus, comprising: displacing, by a shaft, a lift propeller vertically between a lift configuration and a stowed configuration, the lift propeller being mounted to a support structure and being displaced further from the support structure in the lift configuration than in the stowed configuration, wherein the shaft is configured to couple a motor assembly to the lift propeller, the shaft comprising a linear translation section configured to allow linear translation of the lift propeller while transmitting torque to the lift propeller, wherein the shaft is configured to slide vertically through the motor assembly to displace the lift propeller vertically between the lift configuration and the stowed configuration, the lift propeller being vertically displaced between the lift configuration and the stowed configuration, the lift propeller being vertically displaced further from the support structure in the lift configuration than in the stowed configuration.