Secondary Actuation Mechanism for Flight Control Surface Arrestment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing aircraft flight control systems face challenges in preventing uncontrollable flight conditions due to free movement of flight control surfaces caused by primary actuation mechanism failures, which can be exacerbated by adding additional actuators or increasing stiffness, leading to weight and complexity issues.
Innovation Solution
A secondary actuation mechanism comprising a secondary actuator, drive link, and connecting rod is coupled to the control surface, allowing it to move to a default position and retain that position in case of primary actuation failure, minimizing space and power demands through the use of a pyrotechnic actuator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional actuators are provided to prevent free movement of control surfaces, then reliability is improved, but device complexity and weight increase
Solution Approach 1:
The actuation system is segmented into a primary actuator for normal operation and a secondary actuator for emergency arrestment. The secondary actuator is further segmented into multiple independent arrestment devices that can be distributed along the control surface, allowing selective deployment without requiring a complete redundant actuation system.
Solution Approach 2:
Arrestment devices serve as intermediary mechanisms between the primary actuator and the control surface. These devices include a driving component, a driven component, and a connector that transmits force only when needed. The intermediary nature allows the system to maintain simplicity during normal operation while providing reliability when required.
2Reliability
If additional actuators are provided to prevent free movement of control surfaces, then reliability is improved, but weight increases
Solution Approach 1:
The arrestment devices are designed as single-use, disposable components that are activated only in emergency situations. Each arrestment device includes a driving component with stored energy (such as a spring or elastic element) that is released once to arrest the control surface and then remains in a locked position. This eliminates the need for heavy, continuously powered redundant actuators.
Solution Approach 2:
The arrestment devices utilize elastic potential energy stored in springs or elastic elements as a counterweight mechanism. The stored energy in these elastic components provides the necessary force to arrest the control surface without requiring additional active power sources, effectively counterbalancing the weight penalty through passive energy storage.
3Manufacturing precision
If actuation mechanism stiffness is increased to prevent free movement, then control precision is improved, but load demand and actuator size increase
Solution Approach 1:
The system transitions from a static, continuously stiff connection to a dynamic, conditionally engaged connection. During normal operation, the control surface is freely movable and controlled by the primary actuator with standard stiffness requirements. When emergency arrestment is needed, the arrestment devices dynamically engage to provide the necessary positional stability, allowing the system to maintain low power demand during normal operation while achieving high precision when required.
Solution Approach 2:
The system changes the mechanical parameter of stiffness from a constant high value to a variable value that is low during normal operation and high during emergency arrestment. The arrestment devices include elastic elements that remain flexible during normal operation but become rigid when engaged, effectively changing the stiffness parameter based on operational conditions without increasing continuous power demand.
4Reliability
If arrestment devices are added to control surface system, then reliability is improved, but available space is reduced
Solution Approach 1:
The arrestment devices are designed with a nested structure where the driven component is positioned within or alongside the control surface, and the connector folds or retracts when not in use. The driving component can be integrated into the existing actuation mechanism housing or mounted on the control surface structure, allowing multiple functional elements to occupy overlapping or adjacent spaces rather than requiring separate dedicated volumes.
Solution Approach 2:
The arrestment devices utilize the third dimension (depth) by positioning components along the spanwise direction of the control surface rather than only in the chordwise direction. The connector can be arranged to extend perpendicular to the control surface plane or utilize the thickness of the control surface structure, effectively distributing the volume requirement across multiple spatial dimensions and reducing the footprint in any single dimension.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A secondary actuation mechanism for arresting (50) movement of a control surface (22) may include a secondary actuator (52), a drive link (56) coupled to the secondary actuator, and a secondary connecting rod (54) coupled between the drive link and the control surface, wherein the control surface is movable to a default position in response to actuation of the secondary actuator, and the secondary actuator retains the control surface at the default position