Ejection Seat Pan Adjustment via Ratchet Mechanism

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Solution Overview

Problem

Ejection seats lack an effective mechanism to adapt to varying pilot biometrics, particularly in adjusting the distance between the seat pan and the aircraft floor for occupants of different heights, which can affect comfort and safety during ejection.

Innovation Solution

A seat pan adjustment system comprising a guide bracket with a channel and a seat pan mount that translates relative to the guide bracket, utilizing a rod and biasing member to adjust the seat pan's position, with a strap mechanism to facilitate movement and a backdraft damper for control, allowing the seat pan to be adjusted to accommodate different occupant heights.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a fixed seat pan position is used, then the structure is simple and reliable, but it cannot adapt to varying pilot biometrics and heights

Engineering Contradiction:

Improveadaptability to varying pilot biometricsVSAvoidcomplexity of seat pan adjustment mechanism

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The seat pan is transformed from a fixed structure to a dynamically adjustable one through a ratchet mechanism. The mechanism includes a movable seat pan mounted on a track, allowing it to slide forward and backward. A ratchet wheel with teeth engages with pawls to lock the seat pan at selected positions, enabling adaptation to different pilot heights while maintaining structural simplicity and reliability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The adjustment mechanism is segmented into discrete lockable positions using a ratchet wheel with multiple teeth. Each tooth represents a potential stopping position for the seat pan, allowing pilots to select from several predefined height adjustments. This segmentation provides adaptability without requiring continuous adjustment mechanisms, thereby controlling complexity.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If an adjustable seat pan mechanism is added, then adaptability to different occupant heights is improved, but the device complexity increases

Engineering Contradiction:

Improveadjustability of seat pan positionVSAvoidnumber of components in adjustment system

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The ratchet mechanism is designed as a self-service system where the pilot can independently adjust the seat pan position without assistance. The pawl-ratchet engagement automatically locks the seat pan at selected positions, and the system self-regulates through mechanical interaction of its components, reducing the need for complex control systems or additional actuators.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The ratchet wheel acts as an intermediary mechanism between the movable seat pan and the fixed aircraft structure. It mediates the adjustment motion by providing discrete lockable positions through tooth engagement, simplifying the overall mechanism while achieving the desired adjustability function.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If the seat pan can move freely, then adjustability is maximized, but control and stability during ejection are compromised

Engineering Contradiction:

Improverange of seat pan adjustmentVSAvoidstability of seat pan position

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The seat pan system transitions from a completely fixed structure to a dynamically adjustable one with controlled movement. The ratchet mechanism allows the seat pan to be movable during adjustment but automatically locks it in place during ejection, providing both adaptability and reliability at different operational phases.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The ratchet mechanism applies preliminary locking action before ejection occurs. The pawls engage with the ratchet teeth to prevent any unintended movement of the seat pan, ensuring stability is established in advance of the ejection event, thereby preventing position changes during the critical ejection phase.

Inventive Principle:

Principle #9Preliminary anti-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 system enables precise adjustment of the seat pan's position relative to the aircraft floor, enhancing comfort and safety by accommodating various pilot sizes, ensuring a secure and optimal ejection posture for occupants of different heights.

Implementation Method 1

A biasing member is coupled to the rod and configured to force the rod away from the surface of the seat pan mount

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

the guide bracket further includes a backdraft damper located between at least one of the lower rod recess and the horizontal chamber

Methodology Applied

Scientific EffectDamping: Damping

Data Source

PatentEP3828084B1Seat pan adjustment system for ejection seats

Publication Date: 2023.04.12 AMI IND INC

Figure 1
Figure 2A
Figure 2B

AI summary

A seat pan adjustment system (120) for an ejection seat may comprise a guide bracket (124a, 124b) defining a channel (134) and a seat pan mount (122) configured to translate relative to the guide bracket. A support bracket (136) may extend from a surface (128) of the seat pan mount. A rod (132) may be located through a rod opening (138) defined by the support bracket. The rod may be located in the channel. A biasing member (140) may be coupled to the rod and configured to force the rod away from the surface of the seat pan mount.