Pitch Control System With Pressure-Triggered Propeller Pitchlock

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Solution Overview

Problem

Existing pitch control systems in aircraft propellers are prone to undesired feathering during specific operating conditions, such as take-off, leading to increased drag and overspeed risks, particularly in multi-engine configurations where one engine fails.

Innovation Solution

A pitch control system with a controller that detects undesired feathering by monitoring pitch, rotation rate, and torque, and reduces pressure in the propeller's pressure circuits to prevent feathering and pitchlock the blades, using anti-feathering and pitchlock mechanisms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the pitch control system allows automatic feathering to respond to engine failures, then the propeller can reduce drag in complete engine failure, but undesired feathering occurs during partial engine failure and take-off operations

Engineering Contradiction:

Improvepropeller safety in engine failureVSAvoidundesired feathering causing increased drag and overspeed risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The pitchlock mechanism applies a preliminary locking action on the propeller blade pitch before undesired feathering can occur. The mechanism uses a latch that engages with a cam surface to prevent pitch reduction, and this locking action is activated in advance during take-off or partial engine failure conditions to counteract any potential harmful feathering movement before it can develop

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The controller continuously monitors engine operation parameters and propeller performance to detect conditions indicating partial engine failure or take-off operation. When such conditions are detected, the controller activates the pitchlock mechanism to prevent undesired feathering. The system provides feedback-based control by adjusting the pitchlock engagement based on real-time detection of engine power output and propeller response

Inventive Principle:

Principle #23Feedback

2Reliability

If a pitchlock mechanism is incorporated to prevent pitch reduction, then propeller overspeed is prevented, but the system cannot respond to complete engine failure requiring feathering

Engineering Contradiction:

Improvepropeller speed controlVSAvoidability to feather in complete engine failure

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The pitch control system dynamically adjusts its behavior based on operating conditions. The controller monitors engine power output and propeller response characteristics to determine whether to engage the pitchlock mechanism or allow feathering. During take-off or partial failure, the pitchlock is engaged to prevent overspeed. In complete failure, the system detects the total loss of engine power and disengages the pitchlock to allow feathering, thus adapting the system's protective action to the specific failure mode

Inventive Principle:

Principle #15Dynamics

3Ease of operation

If counterweights are located on propeller blades to generate torque forcing blades to feather, then feathering is achieved in hydraulic supply loss, but unwanted feathering occurs during take-off and partial engine failure

Engineering Contradiction:

Improveautomatic feathering in hydraulic failureVSAvoidunwanted propeller feathering during critical operations

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The pitchlock mechanism acts as an intermediary between the hydraulic pitch control system and the propeller blades. Instead of relying solely on counterweights that continuously exert feathering torque, the pitchlock mechanism selectively engages to override the counterweight effect when needed. The controller mediates between the automatic feathering tendency and the need to prevent overspeed by intelligently activating the pitchlock during take-off or partial engine failure while allowing counterweight-driven feathering in complete failure

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

Prevents undesired feathering, maintaining propulsion and safety by ensuring the propeller blades do not increase pitch, even in partial engine failures, thereby enhancing aircraft safety and performance.

Implementation Method 1

at least a coarse pitch pressure circuit configured to receive a pressurised fluid

Methodology Applied

Scientific EffectHydraulic pressure: Hydraulic Press

Implementation Method 2

The controller may be configured to pitchlock the propeller blade by reducing the pressure of the pressurised fluid received by the pitchlock pressure circuit

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Data Source

PatentUS20250305420A1Pitch control system

Publication Date: 2025.10.02 RATIER FIGEAC SAS

AI summary

A pitch control system includes: a coarse pitch pressure circuit configured to receive a pressurised fluid; a pitchlock mechanism configured to pitchlock a propeller blade of a propeller; and a controller configured to detect undesired feathering of a propeller blade. The controller is configured to, in response to detecting undesired feathering of the propeller blade, reduce the pressure of the pressurised fluid received by the coarse pitch pressure circuit so as to stop the propeller blade feathering and simultaneously cause the pitchlock mechanism to pitchlock the propeller blade.