# US 4,394,999 A · Redundant or emergency steering mechanism especially for an aircraft > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,394,999 A - Document ID: US4394999A - Status: Granted - Kind: A - Application number: 06/179,102 - Filed: 1980-08-18 - Granted: 1983-07-26 - Earliest claimed: 1979-08-21 - Assignees: Messerschmitt-Boelkow-Blohm Gesellschaft mit beschraenkter Haftung - Inventors: Ludwig Botzler - Web page: https://patentgrep.com/patent/US4394999A ## CPC - B64C 13/42: having duplication or stand-by provisions - B64C: AEROPLANES; HELICOPTERS ## Abstract A redundant steering mechanism for a craft, especially an aircraft, comprs redundant control components which become effective when the normal steering components become disabled as a result of an electrical power supply failure. The redundant control components do not affect the normal control system but are effective even if the electrical power supply of the craft should fail. The redundant control components are operated by a hydraulic or pneumatic medium acting as a signal carrier. The control signal is a multicomponent signal, one component of which is derived from the pilot's control stick and other signal components are derived from such factors as the speed, the angle of attack and so forth. These signal components are superimposed to form the mechanical emergency control signal for operating a hydraulic or pneumatic steering element. ## Claims ### Claim 1 A redundant emergency control mechanism for steering an aircraft, comprising pilot controlled mechanical steering means (1, 2), first pressure transducer means (3) operatively connected to said pilot controlled mechanical steering means (3) for converting a movement of said mechanical steering means into a first hydraulic steering control signal component representing a pilot control action, operating condition sensor means (12) which are independent of an electrical power supply for sensing instantaneous flight operating conditions, second pressure transducer means (13) operatively connected to said operating condition sensor means (12) for converting flight operating condition representing signals into flight operating condition representing second hydraulic steering control signal components, pressure operated control actuator means (18) including a source of pressure (P) and conduit means operatively connecting said control actuator means (18) to said first and second pressure transducer means for receiving said first and second hydraulic steering control signal components in a superimposed manner in said control actuator means (18) for converting the resulting combined signal into a mechanical steering control action when an electrical power supply failure occurs in the aircraft, said mechanism further comprising pressure operated power actuator means (25), valve means (23) operatively connecting said second pressure transducer means (13) to said pressure operated power actuator means (25), and mechanical linkage means (22, 24, 26) operatively interconnecting the output (22) of said pressure operated control actuator means (18) to the respective outputs (26, 24) of said valve means (23) and of said pressure operated power actuator means (25), whereby an operation of said control actuator means (18) overrides the normal automatic operation of said power actuator means (25). ### Claim 2 (depends on 1) The mechanism of claim 1, wherein said second pressure transducer means (13) comprise throttling valve means (14), whereby said second pressure signal component from said sensor means operate said throttling valve means for a stabilizing action. ### Claim 3 (depends on 1) The mechanism of claim 1, wherein said pressure operated control actuator means (18) comprise housing means, separator wall means (32) in said housing means forming two chambers (29, 30) in said housing means, piston means (20) operatively located in one of said chambers, control slide valve means (19) operatively located in the other of said chambers, spring means (31, 33) for biasing said control slide valve means in said other chamber, piston rod means (22) operatively connected to said piston means (20) and extending through said control slide valve means, and fluid conduit means (28) operatively extending through said piston rod means for actuating said piston means (20) by said resulting combined signal which is proportional to a displacement of said mechanical steering means and proportional to said instantaneous operating conditions. ### Claim 4 (depends on 3) The mechanism of claim 3, further comprising fluid conduit means operatively interconnecting said first and second pressure transducer means and said control actuator means to produce a differential pressure for operating said control actuator means. ### Claim 5 (depends on 3) The mechanism of claim 3, wherein said slide valve means (19) is connected in series between said first and second pressure transducer means on the one hand and said piston means (20) in said other chamber whereby said piston means operates as a power amplifier. ### Claim 6 (depends on 1) The mechanism of claim 1, wherein said first pressure transducer means (3) comprises housing means, flow passage means in said housing means, pressure supply inlet means, pressure return outlet means and pressure medium flow control means in said housing means, slide valve means (5, 5') in said housing means, means (2) operatively connecting said slide valve means (5, 5') to said steering means (1), said slide valve means (5, 5') being operatively arranged in said housing means, and comprising two spaced piston means and variable flow throttling means (6, 7) operatively arranged between said spaced piston means, said pressure transducer means further comprising fixed flow throttling means operatively arranged to bypass the respective slide valve piston means for making said first pressure signal component proportional to a displacement of said mechanical steering means. ### Claim 7 A method for a redundant controlling or steering an aircraft when a failure of the electric power supply of the aircraft occurs, comprising the following steps: operatively connecting, in response to said electric power supply failure a pressure supply source to a hydraulic pressure operated control actuator means (18), producing a first hydraulic pressure signal component representing a pilot steering action (1, 2, 3), producing independently of any electrical power supply a second hydraulic pressure signal component representing a sensed instantaneous flight operating condition (12, 13, 14), superimposing said first and second hydraulic pressure signal components in said control actuator means to produce a combined hydraulic steering control signal and using the combined hydraulic steering control signal for activating said hydraulic pressure operated control actuator means (18) to produce a steering action without the use of any electrical power.