Thrust Reverser Actuator Load Limiter Design
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Solution Overview
Problem
The existing thrust reverser actuation systems face issues with weight optimization and risk of permanent damage due to uneven load distribution and excessive torque during actuator failures, leading to potential damage to actuators and motor components.
Innovation Solution
A drive arrangement with a third, smaller actuator equipped with a load limiter that reacts excessive loads by applying a braking load to the actuator housing, reducing the risk of damage and allowing for weight savings by differing actuator sizes based on load requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If smaller, lighter weight actuators are used in intermediate positions to save weight, then weight is reduced, but the actuators are less strong and only able to bear smaller loadings before sustaining permanent damage
Solution Approach 1:
The thrust reverser system is divided into multiple actuator zones (outer actuators near guide tracks and intermediate actuators) with different strength requirements. The outer actuators are designed to withstand maximum loads from fan blade failures, while intermediate actuators can be lighter since they experience smaller loadings during normal operation.
Solution Approach 2:
Different actuator designs are applied to different locations based on local load requirements. Outer actuators positioned near guide tracks are made stronger to handle structural loads during fan blade failures, while intermediate actuators are optimized for weight savings since they bear smaller loads during normal thrust reverser operation.
2Reliability
If the no-back device gain is slightly greater than unity to ensure braking load is larger than required, then uncontrolled movement is prevented, but excessive torque is applied to the intermediate actuator during actuator failure
Solution Approach 1:
A torque limiter device is incorporated into the intermediate actuator to provide beforehand protection against excessive torque. The torque limiter is designed to release upon application of excessive torque, preventing permanent damage to the intermediate actuator while allowing the no-back device to maintain reliable braking function during normal operation.
Solution Approach 2:
The torque limiter device converts the potentially harmful excessive torque into a beneficial protective mechanism. When excessive torque is applied during actuator failure, the torque limiter releases to protect the intermediate actuator, transforming a harmful condition into a controlled safety feature.
3Stability of the object's composition
If all actuators are driven in synchronism by a single motor, then coordinated movement is achieved, but during actuator failure the undriven actuator places excessive compressive loading on the intermediate actuator
Solution Approach 1:
The torque limiter device provides beforehand protection against the excessive compressive loading that occurs during actuator failure. When one actuator fails and the cowl pivots, the torque limiter on the intermediate actuator releases to prevent permanent damage from the reflected loads through lever action.
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 load limiter effectively mitigates the risk of permanent damage to actuators by limiting excessive loads and torque, enabling controlled movement of the thrust reverser cowl while achieving weight savings through varying actuator sizes.
Implementation Method 1
the load limiter being operable to apply a braking load to the actuator member to resist rotation thereof, thereby reacting applied torque to the housing of the third actuator
Data Source
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AI summary
A thrust reverser drive arrangement for driving a thrust reverser cowl for movement relative to first and second guide tracks is described which comprises a first actuator (16a) located, in use, close to the first guide track (12), a second actuator (16b) located, in use, close to the second guide track (12), and a third actuator (16c), the actuators (16) being arranged to be driven in synchronism and at the same speed by a drive motor (18) to drive the cowl (10) for movement, and wherein the third actuator (16c) is provided with a load limiter (40) to limit the transmission of loads through the third actuator (16c) in the event that the third actuator (16c) is subject to a compressive loading greater than a predetermined level.