Translational Thrust Control via Mechanical-Hydraulic Feedback
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Solution Overview
Problem
Conventional variable pitch propeller systems are unsuitable for high-speed rotary-wing aircraft as they require independent control of propeller blade pitch to manage translational thrust, leading to potential torsional instability due to the interplay between the Electronic Control Unit (ECU) and propeller governor, which can result in overshoots and instability.
Innovation Solution
A mechanical-hydraulic control system integrated with a Fly-By-Wire (FBW) system that adjusts propeller pitch using a propeller pitch controller, hydraulic system, and shuttle valve system to maintain precise pitch control, allowing for independent thrust management without affecting engine RPM, utilizing a propeller pitch change piston and oil transfer/position feedback tube to control blade pitch between high, low, and fail-safe flat positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional propeller governor is used to control engine RPM by changing propeller blade pitch, then engine speed can be maintained, but torsional instability and overshoot occur due to interplay between the governor and ECU
Solution Approach 1:
The patent removes the propeller governor from the control system entirely, extracting the problematic component that causes torsional instability. Instead of using a governor to control RPM through pitch changes, the system uses direct FBW control of the propeller pitch controller, eliminating the source of control conflict between governor and ECU.
Solution Approach 2:
The patent replaces the mechanical propeller governor system with an electronic control system. The FBW system electronically commands the propeller pitch controller, which uses hydraulic actuators instead of mechanical flyweights and linkages. This substitution eliminates the mechanical feedback loop that causes instability while maintaining RPM control capability.
2Adaptability or versatility
If variable pitch propeller systems are used for translational thrust control, then thrust can be adjusted independently of engine RPM, but control precision is reduced due to governor-ECU interplay
Solution Approach 1:
The patent implements a closed-loop feedback system where the FBW system receives input from aircraft state sensors and commands the propeller pitch controller accordingly. The propeller pitch position is precisely controlled through electronic feedback from the pitch controller to the FBW system, eliminating the imprecise mechanical feedback of conventional governors and enabling accurate independent thrust control.
Solution Approach 2:
The patent introduces a propeller pitch controller as an intermediary device between the FBW system and the propeller blades. This intermediary precisely translates electronic commands into accurate blade pitch positions using hydraulic actuators, providing the precision needed for independent thrust control without the errors introduced by governor-ECU interplay.
3Adaptability or versatility
If conventional propeller systems are used, then结构简单 (structure is simple), but they cannot provide independent thrust control for high-speed rotary-wing aircraft
Solution Approach 1:
The patent creates a multi-functional propeller control system that can independently manage both thrust and RPM. The FBW system integrates control of the main rotor and translational thrust system, while the propeller pitch controller handles pitch adjustments. This universal control architecture enables the propeller system to perform multiple functions (thrust control, RPM maintenance, flight regime adaptation) that conventional single-function propeller systems cannot achieve.
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 provides stable and confident pitch angle control of propeller blades, ensuring steady torque and thrust production, reducing the risk of torsional instability and allowing for precise thrust management across various flight regimes.
Implementation Method 1
Hydraulic fluid such as a lubricating oil travels to and from the propeller dome via the oil transfer/position feedback tube
Implementation Method 2
The relatively large propeller pitch change piston area allows large forces to be reacted with moderate pressures
Implementation Method 3
a mechanical-hydraulic control system. The mechanical-hydraulic control system is operated in response to a propeller pitch controller
Implementation Method 4
The propeller blades are pitched through a respective pitch change linkage in response to translation of a propeller pitch change piston
Data Source
AI summary
A translational thrust system for a high speed rotary-wing aircraft includes a propeller system driven by a propeller gearbox, a hydraulic system, and a mechanical-hydraulic control system. The mechanical-hydraulic control system utilizes a hydraulic fluid which travels to and from a propeller dome via an oil transfer/position feedback tube which translates with a propeller pitch change piston. Translation of the oil transfer/position feedback tube and the propeller pitch change piston pitches the blades between high (coarse) and low (fine) pitch positions.