Parametric SolidWorks assembly of the F-35B swivel duct showing all three stages — Parametric SolidWorks assembly, all three duct stages

Independent Study / Aerospace

F-35B 3-Bearing Swivel Duct

Kalan Ferguson / 2025 / Independent / SolidWorks

Platform

F-35B Lightning II

System

3BSD STOVL nozzle

Tool

SolidWorks

Type

Independent study

Overview

The 3-Bearing Swivel Duct (3BSD) is the vectoring nozzle system that enables Short Takeoff and Vertical Landing (STOVL) capability on the F-35B Lightning II. It redirects engine exhaust thrust downward through a 3-stage rotational duct assembly, allowing the aircraft to transition between conventional forward flight and vertical hover.

This was an independent study undertaken outside of coursework. Starting from a reference CAD file, the entire assembly was reverse-engineered and rebuilt as a fully constrained parametric model in SolidWorks.

Parametric rebuild

The original reference geometry was deconstructed into its component duct sections, bearing interfaces, and actuator connection points. Each component was then remodelled parametrically so that dimensional changes propagate through the full assembly, maintaining geometric constraints across the entire thrust-deflection range.

The key challenge was capturing the non-orthogonal rotational synchronisation between the three duct stages. Each stage rotates about a different axis, and the relative rotation angles must be coordinated precisely to maintain a continuous flow path without internal volume interference.

Reverse isometric showing duct stage colouring

Rear view showing nozzle exit geometry

Motion study and validation

A SolidWorks motion study was configured to simulate the full deflection sequence from horizontal (forward flight) to vertical (hover). At each deflection increment, geometric clearance was verified between adjacent duct surfaces, bearing housings, and the surrounding airframe envelope. Mechanical interference was identified at several intermediate positions and resolved through iterative geometric refinement of the duct wall profiles and bearing seat geometry.

Method log

Reverse-engineering of reference CAD geometry into parametric components
Fully constrained assembly with propagating dimensional relationships
Non-orthogonal rotational synchronisation across three duct stages
Motion study validation for geometric clearance at each deflection angle
Interference detection and iterative resolution of volumetric conflicts

This project was undertaken independently as a self-directed study of STOVL propulsion systems. It was not assigned as part of any coursework, and reflects a genuine interest in aerospace propulsion and vectoring nozzle mechanics.

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