Ejection Seat Arm Restraint Attenuator for Load Spike Control
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Solution Overview
Problem
Current ejection seat arm restraints may fail to fully deploy due to sudden load spikes, leading to unrestrained arms during windblast, increasing the risk of injury to the seat occupant.
Innovation Solution
An arm restraint assembly with an attenuator system that gradually increases tension in the aircraft cable, using a housing, plunger, and biasing member to ensure the arm restraint fully deploys before separation from the anchor, thereby reducing the likelihood of load spikes and ensuring the arm is securely restrained during ejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sheer pin coupling the aircraft cable to the arm restraint is used to separate the arm restraint from the stationary structure, then the arm restraint can be separated after deployment, but if too great a load is applied too quickly (load spike), the sheer pin may break before the arm restraint is fully deployed
Solution Approach 1:
The patent introduces an attenuator device between the aircraft cable and the arm restraint that gradually increases cable tension during deployment. This cushioning mechanism prevents sudden load spikes by controlling the rate of tension increase, ensuring the sheer pin breaks only after the arm restraint is fully deployed and locked in position, thereby resolving the contradiction between reliable deployment and force management.
2Device complexity
If the arm restraint is coupled directly to the stationary structure via aircraft cable, then the structure is simple, but the arm restraint may not fully deploy before separation due to load spikes
Solution Approach 1:
The patent introduces an attenuator as an intermediary device between the aircraft cable and the arm restraint. This mediator gradually increases cable tension during deployment, preventing load spikes that could cause premature shearing. The attenuator ensures reliable deployment completion while adding only moderate complexity to the overall system, resolving the contradiction between device simplicity and deployment reliability.
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 attenuator system ensures the arm restraint is fully deployed and securely locked before separation, reducing the risk of injury to the seat occupant by managing load spikes and maintaining arm restraint throughout the ejection process.
Implementation Method 1
a biasing member may be located in the housing. The biasing member may be configured to bias the head of the plunger toward the first end of the housing.
Data Source
AI summary
An arm restraint assembly for an ejection seat may comprise a primary arm configured to pivot about a primary arm pivot joint, a first cable portion coupled to the primary arm, and an attenuator coupled to the first cable portion. The first cable portion may be configured to pivot the primary arm about the primary arm pivot joint. The attenuator may include a housing and a plunger having a head located in the housing. The head of the plunger may be biased toward a first end of the housing.