Variable-Geometry Aircraft Air Inlet With Rack-and-Pinion Actuation

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Solution Overview

Problem

Existing aircraft propulsion system air inlets with variable geometry face challenges due to the complexity, size, and mass of traditional linear actuators, which are cumbersome and difficult to integrate, and require complex synchronization for controlling the movable upstream part.

Innovation Solution

A rack and pinion connection system is integrated into the fixed downstream part, guided by guide members, to move the movable upstream part, providing precise and durable control of the air intake, reducing size and mass by using a rack and pinion connection with guide bars and teeth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional linear actuators are used to move the movable upstream part, then the air inlet can achieve variable geometry adaptation, but the device complexity, size, and mass increase significantly

Engineering Contradiction:

Improvevariable geometry adaptationVSAvoidcomplexity of linear actuators and synchronization

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces traditional linear actuators (hydraulic, pneumatic, or electric) with a rack and pinion mechanical connection system. The fixed downstream part includes a toothed wheel that engages with teeth on a drive bar connected to the movable upstream part, converting rotational motion to linear motion mechanically without requiring complex actuator systems

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent integrates the rack and pinion connection directly into the fixed downstream part structure, merging the actuation mechanism with the air inlet housing. The guide members are also integrated into the fixed downstream part, combining multiple functions (support, guidance, and actuation) into a unified structure

Inventive Principle:

Principle #5Merging (Combining)

2Adaptability or versatility

If traditional linear actuators are used to move the movable upstream part, then the air inlet can achieve variable geometry adaptation, but the size and mass of the air inlet increase

Engineering Contradiction:

Improvevariable geometry adaptationVSAvoidmass of linear actuators

Core Design Contradiction:

Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

The patent replaces heavy linear actuators with a lightweight rack and pinion mechanical connection system. The toothed wheel and drive bar with teeth provide the necessary mechanical advantage and motion conversion without requiring bulky hydraulic cylinders or electric linear actuators

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

Instead of using linear actuators that push or pull the movable upstream part directly, the patent inverts the approach by using a rotating toothed wheel that engages with the drive bar, converting rotational motion to linear motion in a more space-efficient and lighter manner

Inventive Principle:

Principle #13The other way round (Inversion)

3Adaptability or versatility

If traditional linear actuators are used to move the movable upstream part, then the air inlet can achieve variable geometry adaptation, but the integration into thin air inlet structures becomes difficult

Engineering Contradiction:

Improvevariable geometry adaptationVSAvoidintegration difficulty in thin structures

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent integrates the rack and pinion connection directly into the fixed downstream part structure. The toothed wheel and guide members are incorporated as integral parts of the housing, eliminating the need for separate actuator assemblies that would be difficult to fit into thin air inlet structures

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces bulky linear actuators with a compact rack and pinion mechanism that can be easily integrated into thin-walled structures. The mechanical connection is simpler and requires less internal space, making it suitable for thin air inlet designs

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Adaptability or versatility

If traditional linear actuators are used to move the movable upstream part, then the air inlet can achieve variable geometry adaptation, but the control synchronization becomes complex

Engineering Contradiction:

Improvevariable geometry adaptationVSAvoidsynchronization control

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The patent replaces complex actuator synchronization control with a simple mechanical rack and pinion connection. The toothed wheel and drive bar provide inherent mechanical synchronization, eliminating the need for complex control systems to coordinate multiple actuators

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 allows for efficient adaptation of internal air flow to various flight speeds, reducing noise and size, while enhancing reliability and ease of synchronization, making it suitable for supersonic aircraft propulsion systems.

Implementation Method 1

a rack and pinion connection making it possible to move the displacement member and the movable upstream part

Methodology Applied

Scientific EffectRack and pinion: Rack and Pinion

Data Source

PatentEP4267838B1Air inlet for an aircraft propulsion unit comprising a member for moving a movable upstream portion and method for using such an air inlet

Publication Date: 2025.10.22 SAFRAN NACELLES

Figure 1A~2A
Figure 2B~4A
Figure 4B~5B

AI summary

An air inlet (5) for an aircraft propulsion unit (8) comprising a movable upstream portion (1), a stationary downstream portion (2) and at least one member (3) for longitudinally translating the movable upstream portion (1) between a retracted position in which the movable upstream portion (1) is adjacent to the stationary downstream portion (2), and an extended position (P2) in which the movable upstream portion (1) is separated from the stationary downstream portion (2), the moving member (3) comprising at least one guiding bar (30) connected to the movable upstream portion (1) and a drive bar (33) comprising a plurality of teeth (34), the stationary downstream portion (2) comprising, for each moving member (3), a gear wheel (24) configured to co-operate with the teeth (34) in order to form a rack-and-pinion connection and at least one guiding member (25) of the guiding bar (30).