Removable Wear Elements in Droop Rings for Rotor Blade Droop
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Solution Overview
Problem
Rotor blades in rotorcraft experience significant droop due to gravity at low RPMs or when stopped, which can lead to loss of aircraft controllability and increased wear on components, as existing droop limiting systems are either ineffective or require costly maintenance.
Innovation Solution
A droop limiting system featuring a droop ring with removable wear elements and a channel structure that allows for adjustable friction, preventing excessive droop by using flap stops to contact the droop ring's outer surface, thereby limiting downward displacement and reducing wear on the rotor assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a droop limiting system is implemented to prevent excessive droop at low RPMs, then rotor blade stability is improved, but device complexity increases due to additional components like droop rings and wear elements
Solution Approach 1:
The droop ring is segmented into a body and removable wear elements, allowing the wear elements to be separated and replaced independently from the main droop ring structure. This segmentation enables maintenance of stability functionality while simplifying the overall system by allowing easy replacement of wear-prone components.
Solution Approach 2:
The wear elements are designed to be removable and replaceable, transforming a static component into a dynamic system where parts can be adjusted or replaced based on wear conditions. This dynamic approach maintains stability while reducing long-term complexity through ease of maintenance.
2Reliability
If fixed wear elements are used in the droop ring, then initial friction characteristics are optimized, but maintenance costs increase due to inability to replace worn elements
Solution Approach 1:
The wear elements are segmented as separate removable components from the droop ring body, enabling independent replacement of worn wear elements without replacing the entire droop ring assembly. This maintains optimal friction characteristics through replaceable elements while dramatically improving ease of repair.
Solution Approach 2:
The wear elements are designed to be discarded when worn and replaced with new elements, while the main droop ring body is recovered and reused. This approach maintains reliable friction characteristics through fresh wear surfaces while reducing maintenance costs by keeping the expensive droop ring body in service.
3Reliability
If wear elements extend above the end surface to space the droop ring from the channel, then friction control is improved, but manufacturing complexity increases due to cavity formation and element insertion
Solution Approach 1:
The manufacturing process is segmented into forming cavities in the droop ring body and separately manufacturing wear elements that fit into these cavities. This segmentation improves friction control through precisely fitted wear elements while making manufacturing more manageable by breaking down the complex task into simpler, modular steps.
Solution Approach 2:
The wear elements are nested within cavities formed in the droop ring body, with the wear elements extending above the end surface. This nesting arrangement improves friction control by ensuring proper positioning and spacing while simplifying manufacturing by allowing the wear elements to be inserted into pre-formed cavities rather than requiring complex integrated manufacturing.
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 effectively limits rotor blade droop, extends service life, reduces maintenance costs, and maintains rotor assembly performance by using replaceable wear elements that avoid wear on critical components, while allowing for greater displacement during flight.
Implementation Method 1
a first wear element disposed at the first end surface, wherein the first wear element is removable, and wherein the first wear element extends above the first end surface and spaces the first end surface apart from the channel
Implementation Method 2
a droop ring slideably disposed in the channel of the droop limiting system
Data Source
AI summary
A rotorcraft having a rotor system including a yoke, a plurality of grip assemblies, each of which is hingedly attach a rotor blade to the yoke, a plurality of flap stops, each flap stop attached to a respective grip assembly, a channel bounded by an upper and lower retaining surfaces, and a droop ring slideably disposed in the channel of the droop limiting system. The droop ring has a body with an inner surface, an outer surface, and a first end surface between the inner surface and the outer surface. The droop ring further has a first wear element removably disposed at the first end surface and extending above the first end surface and spaces the first end surface apart from the channel. Each flap stop is arranged to contact the outer surface of the droop ring and limit a downward droop of the respective rotor blade.