Aircraft Cowl Door Actuator With No-Back Ball Screw Architecture
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Solution Overview
Problem
Existing aircraft cowl door actuators rely on hydraulic power systems, which are heavy, require complex hose lines, and lack efficient electromechanical alternatives that are cleaner, greener, and more modular.
Innovation Solution
An electromechanical actuator architecture with a modular design incorporating a motor, clutches, a ball screw, and a coaxial external cylinder, featuring a skewed clutch and no-back unit to maintain position during torque cessation, along with a centralized control system for multiple actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If hydraulic power systems are used for cowl door actuators, then sufficient power and force can be achieved, but the system becomes heavy and requires complex hose lines
Solution Approach 1:
The patent replaces the hydraulic power system with an electromechanical actuation system. The motor-driven ball screw mechanism converts rotational motion to linear motion, providing the necessary actuation force without requiring hydraulic fluid, hoses, or pumps. This substitution eliminates the heavy hydraulic infrastructure while maintaining sufficient force for cowl door operation.
Solution Approach 2:
The patent extracts and removes the hydraulic system components (fluid, hoses, pumps) from the actuation system, retaining only the essential mechanical elements (motor, ball screw, clutch) needed to generate and transmit force. This extraction reduces system weight and complexity while preserving the core force-generating capability.
2Power
If hydraulic power systems are used for cowl door actuators, then sufficient power can be achieved, but the system requires complex hose lines and infrastructure
Solution Approach 1:
The electromechanical system replaces the complex hydraulic infrastructure with a self-contained motor-driven mechanism. The motor, ball screw, and clutch assembly provide all necessary power transmission functions without external hydraulic lines, pumps, or fluid management systems, significantly reducing overall system complexity.
Solution Approach 2:
The electromechanical actuator is a self-contained unit that generates and transmits its own power internally. The motor drives the ball screw mechanism directly, and the clutch manages power flow without requiring external hydraulic infrastructure. This self-service capability eliminates the need for complex hose lines and external power transmission infrastructure.
3Power
If a ball screw mechanism is used for actuator extension, then efficient torque transfer can be achieved, but the system lacks position maintenance capability when torque ceases
Solution Approach 1:
The clutch assembly acts as an intermediary between the motor and the ball screw mechanism. It selectively engages and disengages power transmission, and crucially, maintains the mechanical connection and position when the motor is not actively driving the system. This intermediary component ensures both efficient torque transfer during actuation and reliable position maintenance during idle periods.
Solution Approach 2:
The clutch is pre-configured to automatically engage and lock the ball screw mechanism in position when motor torque ceases. This preliminary action of automatic engagement ensures position maintenance without requiring additional active components or continuous power input, providing reliable position holding as a built-in feature of the mechanism.
4Device complexity
If a compact electromechanical design is implemented, then system weight and complexity are reduced, but vibration resistance may be compromised
Solution Approach 1:
The patent employs a nested arrangement where the ball screw is housed within a protective cylindrical casing, and the clutch mechanism is integrated within the same compact envelope. This nesting of components achieves a compact design that minimizes spatial footprint while the layered protective structures inherently dampen and resist vibration effects on the precision mechanical elements.
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 electromechanical actuator provides a lighter, more efficient, and vibration-resistant actuation system with a compact design, enabling scalable and centralized control, reducing complexity and environmental impact.
Implementation Method 1
a ball screw with two coaxial external cylinders. Torque generated for actuator extension is transferable to the ball screw
Implementation Method 2
at least the first clutch is configured to generate a resistive torque during rotation which is proportional to an applied axial load
Implementation Method 3
a no-back unit including a friction clutch and a one-way clutch and a ball screw with two coaxial external cylinders
Data Source
AI summary
An electromechanical actuator architecture is provided for a cowl door of an aircraft engine nacelle. The electromechanical actuator architecture includes a first clutch, a no-back unit including a friction clutch and a one-way clutch and a ball screw with two coaxial external cylinders. Torque generated for actuator extension is transferable to the ball screw and the coaxial external cylinder via the first clutch. During actuator retraction, cowl door weight and an aerodynamic load compress the coaxial external cylinder and the ball screw with loads that are transferred to the no-back unit, which is configured to maintain actuator position in an event generation of the torque ceases.