Cowl Door Clutch Assembly to Limit HOR Retraction Loads

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Solution Overview

Problem

Aircraft engine cowls require robust hold-open-rods (HORs) to manage both cowl loads and additional loads from electro-mechanical actuators during retraction, leading to oversized and heavy engine nacelles due to the need for hydraulic actuators to handle compressive loads and potential actuator-induced loads.

Innovation Solution

An actuator assembly with a clutch assembly, including a friction disc pack and elastic element, limits the actuator's retraction capability when the cowl door is supported by the HOR, allowing the HOR to be sized only for cowl loads, reducing the overall weight and size of the engine nacelle by preventing the actuator from applying additional loads during retraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If hydraulic actuators are used to handle both cowl loads and actuator-induced loads during retraction, then the system can manage all loads, but the HORs and nacelle become oversized and heavy

Engineering Contradiction:

Improveload management capabilityVSAvoidnacelle weight

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

A clutch assembly is introduced as an intermediary mechanism between the electro-mechanical actuator and the drive train. The clutch includes friction discs and a spring that engage to transmit torque only when the actuator is driving the cowl door, not when the HOR supports the door weight. This mediator prevents the actuator's retraction capability from creating additional loads on the HOR, allowing the HOR to be sized for cowl loads only.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent extracts the weight-bearing function from the actuator-HOR system by using the clutch to disconnect the actuator from the drive train during HOR-supported retraction. This separates the load-bearing responsibility from the actuator, allowing the HOR to be optimized for cowl loads only, thereby reducing the overall nacelle weight and size.

Inventive Principle:

Principle #2Taking out (Extraction)

2Adaptability or versatility

If the actuator is designed to power both extension and retraction operations, then the system achieves full operational capability, but the HOR must be oversized to handle actuator-induced loads

Engineering Contradiction:

Improveactuator operational capabilityVSAvoidHOR load capacity requirement

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The clutch assembly dynamically engages and disengages based on the operational state. During extension, the clutch is engaged to transmit actuator torque to the drive train. During retraction when the HOR supports the door, the clutch disengages to prevent actuator torque from loading the HOR. This dynamic behavior allows the actuator to maintain full operational capability while the HOR is sized for static cowl loads only.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The drive train is segmented into two independent load paths: one for extension (actuator-driven) and one for retraction (HOR-supported). The clutch acts as a separator that directs loads appropriately. This segmentation allows the HOR to be optimized for its specific function of supporting cowl door weight without needing to accommodate additional actuator-induced loads.

Inventive Principle:

Principle #1Segmentation

3Power

If the clutch assembly is engaged to transmit actuator torque, then the actuator can drive the cowl door, but additional loads are applied to the HOR during retraction

Engineering Contradiction:

Improveactuator drive capabilityVSAvoidload on HOR

Core Design Contradiction:

PowerVSForce

Solution Approach 1:

The clutch assembly serves as a conditional intermediary that transmits actuator torque only when appropriate. The friction discs and spring mechanism engage during extension to transmit power, but disengage during HOR-supported retraction. This selective mediation allows the actuator to provide drive capability when needed while preventing it from creating additional loads on the HOR during retraction operations.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This solution reduces the size and weight of the engine nacelle by allowing the HOR to be sized for cowl loads alone, eliminating the need for oversized HORs and reducing the overall weight, while ensuring safe and controlled cowl door operation.

Implementation Method 1

a friction disc pack and elastic element, limits the actuator's retraction capability

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

a friction disc pack and elastic element, limits the actuator's retraction capability

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS11987371B2Drive-through friction clutch as a tensile load disconnect

Publication Date: 2024.05.21 HAMILTON SUNDSTRAND CORP

AI summary

An actuator assembly for a cowl door is provided. The actuator assembly includes a housing, an actuator configured to drive cowl door extension and cowl door retraction and to support the cowl door during the cowl door extension and the cowl door retraction and a clutch assembly interposed between the actuator and the housing. The clutch assembly is configured to engage a capability of the actuator to drive the cowl door retraction when the cowl door loads the actuator.