Elevator Variable Feel Unit Single Cam Mechanism
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Solution Overview
Problem
Conventional aircraft elevator control systems are complex, heavy, and lack flexibility in tailoring feel forces, with backlash at neutral positions, making them undesirable for modern aircraft pilot controls.
Innovation Solution
A lightweight, simplified elevator variable feel unit utilizing a single cam and roller mechanism with base and variable feel springs, and a detent bias device to provide customizable feel forces and maintain constant breakout force across airspeed configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bi-directional hinge-type cam roller mechanisms are used, then centering and variable feel functionality are achieved, but the mechanism becomes complex and heavy
Solution Approach 1:
The patent merges the centering function and variable feel function into a single integrated cam mechanism. The cam profile is specifically designed to provide both the centering force (returning the control column to neutral) and the variable feel (progressive resistance) simultaneously, eliminating the need for separate bi-directional hinge mechanisms and reducing overall system complexity
Solution Approach 2:
The single cam mechanism serves multiple functions: it provides centering force, variable feel, and backlash elimination. By designing the cam profile to incorporate all these functions, the patent achieves multi-functionality that reduces the number of components needed while maintaining reliable operation
2Reliability
If conventional bi-directional hinge-type cam roller mechanisms are used, then centering and variable feel functionality are achieved, but the mechanism becomes heavy
Solution Approach 1:
The patent merges the centering function and variable feel function into a single integrated cam mechanism. The cam profile is specifically designed to provide both the centering force (returning the control column to neutral) and the variable feel (progressive resistance) simultaneously, eliminating the need for separate bi-directional hinge mechanisms and reducing overall system complexity
Solution Approach 2:
The patent extracts and eliminates unnecessary components from the conventional mechanism. By removing the bi-directional hinge, multiple cams, and associated linkages, and replacing them with a single optimized cam mechanism, the overall weight of the variable feel unit is significantly reduced while maintaining all required functions
3Reliability
If conventional cam roller mechanisms are used, then variable feel is provided, but backlash occurs at neutral position
Solution Approach 1:
The patent inverts the conventional approach by designing the cam profile to maintain continuous contact with the follower throughout the entire range of motion. The cam surface is shaped so that the follower remains pressed against the cam at all times, eliminating gaps and backlash that occur in conventional mechanisms when direction changes occur at the neutral position
4Reliability
If conventional cam roller mechanisms are used, then variable feel is provided, but flexibility for tailoring feel forces is limited
Solution Approach 1:
The patent enables flexible tailoring of feel forces by allowing modification of the cam profile parameters. By changing the cam surface geometry, radius, and curvature characteristics, different feel curves can be achieved to match various aircraft types and operational requirements. The system can be customized by adjusting cam design parameters without changing the fundamental mechanism structure
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves a compact, lightweight, and customizable variable feel unit that enhances pilot control precision and safety by adjusting feel forces based on airspeed and control column movement, maintaining consistent breakout forces and reducing the impact of vibrations.
Implementation Method 1
Two base feel centering springs attached to a non-pivoting end of the cam follower arm keep the roller on the cam, and provide the base feel force and a centering function
Implementation Method 2
The variable feel spring has a minimum preload and does not add to the feel at low airspeed. When the control column is moved, the movement causes an increase in the extension of the base feel springs, thus increasing the feel forces at the column
Implementation Method 3
A cam attaches by a spline to the input shaft and input crank of the feel unit. The input crank, connected to the control column torque tube, turns the shaft and the cam. A cam follower arm assembly has a roller that causes the cam follower arm to pivot as the cam is pivoted due to movement of the control column
Data Source
AI summary
An elevator variable feel unit for aircraft pilot control. The variable feel unit has a single cam and a roller unit. The cam attaches by a spline to the input shaft and input crank of the feel unit. The input crank, connected to the control column torque tube, turns the shaft and the cam. A cam follower arm assembly has a roller that causes a cam follower arm to pivot as the cam is pivoted due to movement of the control column. Two base feel centering springs between the cam follower arm and a fixed point to keep the roller on the cam, and provide the base feel force and a centering function. In a base feel position, the preload on the base feel spring keeps the variable feel unit in a detent position. The variable feel spring has a minimum preload and does not add to the feel at low airspeed. When the control column is moved, the movement causes an increase in the extension of the base feel springs, thus increasing the feel forces at the column. The feel at the control column increases with the amount of column movement. In this base feel configuration, the variable feel spring does not stretch throughout the full movement of the control column. As the airspeed increases, the elevator feel actuator extends to change the configuration of the feel mechanism in the feel unit, by rotating the variable feel arm up as the airspeed increases. When the control column is moved at higher airspeed, it causes an increase in the extension of the variable feel springs, as well as base feel springs. These two forces increase the feel forces at the control column. Increased rotation of the variable feel arm further causes additional extension of the variable feel spring, and thus the column force.