Filtered Cradle for Aircraft Propulsion Vibration Isolation
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Solution Overview
Problem
The existing suspension methods for turboprops on aircraft wings are limited by structural stiffness, leading to ineffective vibration filtering, increased weight due to rigid alignment requirements, and complex maintenance operations due to the need for simultaneous removal of the gas generator and gearbox.
Innovation Solution
A propulsion assembly with a cradle supporting the gas generator and thrust generator in three distinct suspension planes, using a vibration-filtering flexible connection between the cradle and the aircraft structural element, which provides structural decoupling and axial freedom, eliminating the need for connecting rods and allowing separate maintenance of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If filtering flexible suspensions are used to suspend the turboprop from the cradle, then vibration filtering effectiveness increases with increasing stiffness of the downstream structure, but the structural stiffness of the cradle is limited because the turboprop is cantilevered out to a considerable extent in front of the airplane wing
Solution Approach 1:
The propulsion assembly is divided into two separable parts: the gas generator and the thrust generator (gearbox and propeller). This segmentation allows each component to be independently suspended from the cradle at different planes, enabling the thrust generator to be positioned closer to the wing structure to improve stiffness while the gas generator is suspended separately for vibration isolation.
Solution Approach 2:
A coupling mechanism is introduced as an intermediary between the gas generator and the thrust generator. This coupling mechanism transmits torque while allowing relative movement and misalignment, enabling the two generators to be positioned at optimal locations for both structural stiffness and vibration filtering without requiring rigid connection.
2Stability of the object's composition
If connecting rods or a structural casing are integrated in the propulsion assembly to ensure rigidity and alignment, then the engine presents the required degree of rigidity and alignment, but the weight of the propulsion assembly increases
Solution Approach 1:
The coupling mechanism serves as an intermediary that provides the necessary torque transmission and alignment tolerance without requiring heavy connecting rods or structural casings. It allows the gas generator and thrust generator to maintain proper alignment while being suspended independently, significantly reducing the weight compared to rigid structural connections.
Solution Approach 2:
The system transitions from requiring rigid structural connections to allowing flexible positional adjustment through the coupling mechanism. This parameter change enables the generators to accommodate thermal expansion and vibration-induced movements while maintaining functional alignment, eliminating the need for heavy stabilization structures.
3Device complexity
If the gas generator and gearbox are suspended together as a single unit from two planes, then the suspension structure is simpler, but it becomes necessary to remove the entire propulsion assembly whenever action is desired on either element, lengthening maintenance operations
Solution Approach 1:
The propulsion assembly is segmented into two independently suspendable units: the gas generator and the thrust generator. Each unit has its own suspension planes and mounting points on the cradle, allowing them to be installed and removed independently. This segmentation enables maintenance personnel to access and service either component without removing the entire propulsion assembly, significantly reducing maintenance time.
4Reliability
If flexible suspensions are added in the linkage between the turboprop and the wing, then vibration filtering is improved, but particular flutter modes are generated that make it more complicated to adjust the overall dynamic behavior
Solution Approach 1:
By segmenting the propulsion assembly into independently suspendable gas generator and thrust generator, the vibration filtering is achieved through their separate suspension systems rather than through flexible linkages in the torque transmission path. This eliminates the flutter modes that would be generated by flexible suspensions in the torque path, while still providing effective vibration isolation.
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
This solution enhances vibration filtering effectiveness, reduces weight, simplifies maintenance, and improves the dynamic behavior of the propulsion assembly by allowing independent removal and alignment of the gas generator and thrust generator, while maintaining proper alignment and reducing flutter modes.
Implementation Method 1
a vibration-filtering flexible connection between the rigid cradle and the structural element of the aircraft
Implementation Method 2
a vibration-filtering flexible connection between the rigid cradle and the structural element of the aircraft
Data Source
AI summary
An aircraft propulsion assembly includes: a gas generator coupled by a coupling mechanism to a thrust generator having a structural torque transmission gearbox, and a rigid cradle rigidly supporting the thrust generator in a first suspension plane and the gas generator in distinct second and third suspension planes, the cradle being for securing to a structural element of the aircraft via a vibration-filtering flexible connection.