Tip Rib Mounted Pylon Assemblies for Tiltrotor Load Reduction

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Solution Overview

Problem

Tiltrotor aircraft face challenges in reducing structural loads due to the outboard location of nacelles and the need for rotating them, which increases the size and weight of the airframe structure.

Innovation Solution

A propulsion system with a fixed engine and rotatable pylon assembly, including a spindle gearbox and bearing cartridges, allows for efficient torque transfer between the fixed gearbox and spindle gearbox, enabling the tiltrotor aircraft to operate between helicopter and airplane modes while minimizing structural loads by optimizing the placement of the pylon assembly and bearing systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If nacelles are located outboard and rotated for tiltrotor operation, then vertical takeoff and forward cruising capability is achieved, but the size and weight of the airframe structure increases

Engineering Contradiction:

Improvetiltrotor operation capabilityVSAvoidairframe structure weight

Core Design Contradiction:

Adaptability or versatilityVSWeight of stationary object

Solution Approach 1:

The propulsion system is divided into separate functional components: a fixed engine and gearbox mounted to the airframe, and a rotatable pylon assembly containing the spindle gearbox and proprotor. This segmentation allows the heavy engine to remain fixed while only the lighter pylon assembly rotates, reducing the structural weight required to support rotation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The engine is extracted from the rotatable pylon assembly and fixed to the airframe structure. This extraction eliminates the need for the engine and its mounting structure to withstand rotational forces, allowing for a lighter overall airframe design while maintaining tiltrotor functionality.

Inventive Principle:

Principle #2Taking out (Extraction)

2Adaptability or versatility

If nacelles are located outboard and rotated for tiltrotor operation, then vertical takeoff and forward cruising capability is achieved, but the size of the airframe structure increases

Engineering Contradiction:

Improvetiltrotor operation capabilityVSAvoidairframe structure size

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

By separating the engine mounting from the proprotor mounting through the pylon assembly, the design allows for a more compact integration of components. The pylon assembly can be positioned optimally between the engine and proprotor, reducing the overall footprint of the airframe structure.

Inventive Principle:

Principle #1Segmentation

3Power

If a fixed engine with rotatable pylon assembly is used, then torque transfer efficiency is improved, but the complexity of the propulsion system increases

Engineering Contradiction:

Improvetorque transfer efficiencyVSAvoidpropulsion system complexity

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

A common shaft rotating about the conversion axis serves as an intermediary element to transfer torque from the fixed gearbox to the spindle gearbox. This intermediary shaft provides a direct torque path while accommodating the rotational movement of the pylon assembly, achieving efficient power transfer without requiring complex universal joints or flexible couplings.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The torque transfer mechanism utilizes rotation about the conversion axis (a third dimension relative to the engine output shaft) to bridge the fixed and rotatable components. This dimensional approach simplifies the torque transfer path compared to traditional two-dimensional coupling mechanisms.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 configuration reduces structural loads, allows for efficient operation between helicopter and airplane modes, and provides a more compact and lightweight airframe design, enhancing the aircraft's versatility and performance.

Implementation Method 1

A common shaft that is rotatable about the conversion axis is configured to transfer torque from the output gear of the fixed gearbox to the input gear of the spindle gearbox

Methodology Applied

Scientific EffectTorque transfer: Torque

Implementation Method 2

Inboard and outboard bearing cartridges respectively including inboard and outboard bearing assemblies

Methodology Applied

Scientific EffectBall bearing: Ball Bearing

Data Source

PatentUS10065743B2Tip rib mounted pylon assemblies

Publication Date: 2018.09.04 BELL HELICOPTER TEXTRON INC

AI summary

A pedestal assembly receives a pylon assembly of a tiltrotor aircraft having an airframe including a fuselage and a wing. The pedestal assembly includes inboard and outboard tip ribs that extend above the wing and respectively define inboard and outboard slots. The pedestal assembly also includes inboard and outboard bearing cartridges. The inboard bearing cartridge is received within the inboard slot, is coupled to the inboard tip rib and includes an inboard bearing assembly. The outboard bearing cartridge is received within the outboard slot, is coupled to the outboard tip rib and includes an outboard bearing assembly. The inboard and outboard bearing assemblies are operable to receive the pylon assembly therein such that the pylon assembly is rotatably mounted between the inboard and outboard tip ribs to selectively operate the tiltrotor aircraft between a helicopter mode and an airplane mode.