Two-Piece Spline Shaft for Flight Control Hardover Protection

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Solution Overview

Problem

Current aircraft flight control systems face challenges in managing hardover failures, where control surfaces lose control and become stuck, leading to reduced aircraft controllability due to the complexity and cost of additional redundancy or valving systems.

Innovation Solution

A two-piece spline key coupled shaft system that disengages the actuator from the flight control surface, using a return spring to drive the surface to a safe position, thereby alleviating hardover conditions without relying on additional redundancy or valving.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If additional redundancy or valving systems are employed to prevent hardover failures, then reliability is improved, but device complexity increases

Engineering Contradiction:

Improvehardover failure protectionVSAvoidcontrol system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The shaft is divided into two separate segments (first shaft portion and second shaft portion) that can be coupled together via a spline key. This segmentation allows the system to disengage the actuator from the flight control surface during hardover failures, providing a simple mechanical solution that maintains reliability without adding complex redundant systems.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention extracts the critical function of hardover protection from complex redundant valving systems and implements it through a simple disengageable mechanical connection. By removing the need for multiple valves and redundant actuators, the system achieves hardover failure protection while significantly reducing device complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If multiple surfaces and override valve spool sleeves are used to compensate for hardover failures, then reliability is improved, but manufacturing cost increases

Engineering Contradiction:

Improvehardover failure compensationVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The control surface actuation system is segmented into separable shaft portions that can be independently manufactured and assembled. This segmentation eliminates the need for expensive override valve spool sleeves and multiple compensating surfaces, reducing manufacturing complexity and cost while maintaining hardover failure compensation capability.

Inventive Principle:

Principle #1Segmentation

3Reliability

If additional redundancy systems are implemented, then reliability is improved, but weight increases

Engineering Contradiction:

Improvehardover failure protectionVSAvoidcontrol system weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The invention extracts the essential hardover protection function from heavy redundant hydraulic systems and implements it through a lightweight mechanical disengagement mechanism. By removing unnecessary redundancy components, the system achieves adequate reliability with significantly reduced weight.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentEP2957500B1Systems and methods for operating flight control surfaces

Publication Date: 2019.01.16 THE BOEING CO

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AI summary

Systems and methods for operating flight control surfaces are provided. One system includes a control device having a two piece shaft including a first shaft portion and a second shaft portion, a spline key detachably coupling the first shaft portion and the second shaft portion, and a crankshaft operatively coupling the two piece shaft and a flight control surface. The control device further includes a driving mechanism coupled to the spline key and operable to move the spline key to engage and disengage the first and second shaft portions, wherein the first and second shaft portions are disengaged when a failure to the flight control surface is detected, causing the second shaft portion to drive the flight control surface to a safe position.