Aircraft Accessory Gearbox Stacking for Space-Constrained Mounting

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Solution Overview

Problem

Existing aircraft accessory gearboxes require a large amount of space due to separate mounting pads for each accessory, limiting the ability to accommodate additional accessories and necessitating redesigns, which can impact engine and downstream systems.

Innovation Solution

A stacked arrangement of accessories within the gearbox, utilizing a gear assembly to connect multiple accessories to a single mounting pad, allowing for efficient use of space and enabling simultaneous operation of different accessories.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If separate mounting pads are used for each accessory, then each accessory can be independently mounted, but the gearbox requires a relatively large amount of space

Engineering Contradiction:
ImproveIndependent mounting capabilityVSAvoidGearbox space
Core Design Contradiction:
Ease of operationVSArea of stationary object

Solution Approach 1:

Multiple accessories (starter and generator) are stacked and mounted on a single mounting pad, combining what were previously separate mounting locations into one consolidated mount point, thereby reducing the overall space required in the gearbox

Inventive Principle:
Principle #5Merging (Combining)

2Adaptability or versatility

If the gearbox size is increased to accommodate additional accessories, then more accessories can be installed, but redesign of the gearbox and downstream revisions are required

Engineering Contradiction:
ImproveAccessory accommodation capabilityVSAvoidRedesign requirements
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Instead of expanding the gearbox horizontally to add accessories, the design stacks accessories vertically on top of each other on the same mounting pad, utilizing the vertical dimension to accommodate additional components without increasing the gearbox footprint or requiring redesign

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Area of stationary object

If multiple accessories are mounted on a single mounting pad, then space is optimized, but the accessories must be connected through a stacked arrangement

Engineering Contradiction:
ImproveGearbox space utilizationVSAvoidStacked arrangement complexity
Core Design Contradiction:
Area of stationary objectVSDevice complexity

Solution Approach 1:

The starter and generator are nested in a stacked configuration where one accessory is positioned above the other on the same mounting pad, with drive shafts extending through central openings to connect to the gearbox, creating a compact nested arrangement that optimizes space

Inventive Principle:
Principle #7Nested doll (Nesting)

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 stacked arrangement allows for the addition of multiple accessories without increasing the gearbox size, optimizing space utilization and reducing the need for redesigns, while enabling simultaneous operation of components like starters and generators.

Implementation Method 1

a gear assembly connected between the starter and the generator. The gear assembly enables the starter and the generator to operate at different speeds

Methodology Applied
Scientific EffectGear mechanism: Gear

Data Source

PatentEP4685345A1Accessory gearbox with accessories with a stacked configuration
Publication Date: 2026.01.28 THE BOEING CO
  • EP4685345A1 patent drawingFigure 1
  • EP4685345A1 patent drawingFigure 2
  • EP4685345A1 patent drawingFigure 3

AI summary

An assembly that is operatively connected with a connection assembly (30) to a turbine engine (110) of an aircraft (100). The assembly includes an accessory gearbox (20) with a body (21) configured to be connected to the connection assembly and mounting pads (24) spaced about the body. A first accessory (200a) is mounted to the body at a first one of the mounting pads. A second accessory (200b) is mounted to the first accessory with the first accessory and the second accessory in a stacked arrangement.