Propeller Blade Angle Feedback Ring With Slip-Ring Charge Dissipation
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Solution Overview
Problem
Existing propeller blade angle feedback systems are vulnerable to magnetism and electrical discharges, leading to inaccurate measurements due to errant magnetic fields and lightning strikes, which can cause false triggering and damage to the feedback ring and bearing assemblies.
Innovation Solution
An alternate conductive path is established between the propeller and the engine using an annular slip ring with higher conductivity than the bearing assemblies, connected through an electrically-conductive brush block assembly and grounding cable, to dissipate electrical charges and reduce the risk of arcing and magnetization, thereby protecting the feedback ring and bearing assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phonic wheel (feedback ring) is used to measure propeller blade angle, then blade angle measurement is enabled, but the system becomes vulnerable to magnetism and electrical discharges causing false triggering and inaccurate measurements
Solution Approach 1:
A conductive element is introduced as an intermediary between the propeller shaft and the feedback ring to provide a controlled electrical discharge path. This mediator captures electrical charges before they can reach the feedback ring, preventing false triggering while maintaining measurement capability
Solution Approach 2:
The harmful electrical discharges and magnetic effects are converted into a beneficial protective mechanism by creating a dedicated discharge path through the conductive element. The same electrical charges that would damage the feedback ring are now safely directed through the conductive element to ground, protecting the measurement system
2Strength
If bearing assemblies are used to support the propeller shaft, then mechanical support is provided, but electrical charges accumulate leading to arcing and potential damage to the feedback ring
Solution Approach 1:
The conductive element acts as an intermediary between the bearing assemblies and ground, providing a low-resistance path for electrical charges. This mediator prevents charge accumulation on the shaft by continuously conducting charges to ground, eliminating the harmful arcing effect while preserving the mechanical support function of the bearings
3Measurement precision
If the feedback ring is positioned close to the sensor for accurate measurement, then measurement precision improves, but the risk of arcing across the air gap increases
Solution Approach 1:
The conductive element provides preliminary protection by capturing electrical charges before they can jump the air gap to the feedback ring. This preliminary discharge path prevents the buildup of sufficient charge to cause arcing, allowing the feedback ring to maintain its close position to the sensor for accurate measurement without the arcing hazard
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 solution effectively prevents electrical discharge damage to the bearing assemblies and reduces the risk of false triggering, ensuring accurate propeller blade angle measurements by providing a low-resistance path for electrical charges and minimizing the potential for arcing across the air gap between the feedback ring and sensor.
Implementation Method 1
an alternate conductive path is established between the propeller and the engine using an annular slip ring with higher conductivity than the bearing assemblies
Implementation Method 2
the slip ring connected to an electrically-conductive brush block assembly, the brush block assembly attached to the reduction gearbox and spring loaded to force contact with the slip ring
Data Source
Figure 1
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AI summary
A blade angle feedback ring assembly (200) for an aircraft engine (110) propeller (130) having adjustable angle blades is provided. The feedback ring assembly (200) comprises a feedback ring (204) coupled to rotate with the propeller (130), the engine (110) configured such that a first electrically-conductive path is defined between the propeller (130) and the engine (110) via the feedback ring (204), and an electric current conduction element (502, 602, 702, 802) provided between the propeller (130) and the engine (110) to define a second electrically-conductive path between the propeller (130) and the engine (110) in parallel to the first path, the second electrically-conductive path configured with a lower electrical resistance to conduction between the propeller (130) and the engine (110) than the first electrically-conductive path.