Telescopic Drive Coupling for Aircraft Actuator Stroke Reduction
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Solution Overview
Problem
Existing actuator arrangements for controlling variable air flow fan (VAFN) cowls and thrust reverser cowls in aircraft engines are complex, costly, and heavy due to the need for large stroke actuators and separate control systems, making them unsuitable for all applications, especially when requiring simultaneous operation and failsafe mechanisms.
Innovation Solution
An actuator arrangement featuring a rotatable drive input with a telescopic drive coupling that accommodates movement of thrust reverser cowls, utilizing a motor and drive transmission with a failsafe mechanism, such as a backup motor and control valve, to ensure reliable operation and reduce complexity by allowing independent control of VAFN cowls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate actuators are provided for VAFN cowls and thrust reverser cowls, both being grounded to the airframe structure, then independent control of each system is achieved, but the VAFN actuator must have a very large stroke resulting in significant cost, power and weight implications
Solution Approach 1:
The VAFN actuator is made movable by mounting it on the thrust reverser cowl rather than grounding it to the airframe. This dynamic mounting allows the actuator to move with the thrust reverser cowl, reducing the required stroke length while maintaining independent control capability through the telescopic drive coupling that accommodates the relative movement between the two systems.
Solution Approach 2:
The VAFN actuator is nested on the thrust reverser cowl structure, utilizing the existing moving platform. This nesting arrangement allows the VAFN actuator to piggyback on the thrust reverser cowl's movement, reducing the need for a large independent stroke while still achieving the required nozzle dimension adjustment.
2Weight of moving object
If the VAFN actuator is mounted on the thrust reverser cowl to reduce stroke requirements, then weight and cost are reduced, but the control arrangement must accommodate movement of the thrust reverser cowls
Solution Approach 1:
A telescopic drive coupling is introduced as an intermediary mechanism between the VAFN actuator and the thrust reverser cowl. This coupling accommodates the relative movement between the two components through its telescopic action, allowing the VAFN actuator to maintain its mounting on the moving cowl while still transmitting drive effectively, thus reducing control arrangement complexity.
Solution Approach 2:
The telescopic drive coupling provides a dynamic connection that adapts to the changing relative positions of the VAFN actuator and thrust reverser cowl. This dynamic accommodation eliminates the need for complex control mechanisms to manage the movement differences, simplifying the overall control arrangement.
3Device complexity
If a single actuator is used to control both nozzle dimensions and thrust reverser, then device complexity is reduced, but thrust reverser actuator locks must be released when thrust reverser is not to be deployed making it unsuitable for some applications
Solution Approach 1:
The system is segmented into two independent actuator systems: one for the VAFN cowls and one for the thrust reverser cowls. This segmentation allows each system to operate independently with its own control logic, maintaining thrust reverser deployment reliability while avoiding the need to release locks during normal VAFN operation. The telescopic drive coupling enables the VAFN actuator to be mounted on the thrust reverser cowl without creating functional interference.
Data Source
AI summary
An actuator arrangement comprises an actuator having a rotatable drive input, a motor, and a drive transmission arrangement for transmitting rotary drive from the motor to the rotatable drive input of the actuator, wherein the transmission arrangement includes a telescopic drive coupling.