Fixed-Wing UAV — Airframe Architecture, Internal Layout & Stability-Driven Design

Abstract

This project presents the conceptual and preliminary design of a fixed-wing unmanned aerial vehicle (UAV) developed with an emphasis on airframe architecture, internal subsystem integration, and flight-viable stability characteristics. The design was executed holistically in CAD, progressing beyond external shaping to explicitly account for internal volume allocation, mass distribution, load awareness, and manufacturability. The resulting configuration reflects an airframe that is not only aerodynamically plausible, but structurally and operationally realistic.

1. Design Objectives and Scope

The primary objective of this project was to develop a build-oriented fixed-wing UAV concept, rather than a purely visual or speculative model. Key design goals included:

• Stable, predictable flight behaviour suitable for autonomous operation
• Internally driven geometry shaped around avionics, energy storage, and payload
• Structural realism at major load-bearing interfaces
• A configuration scalable toward fabrication and testing

The scope of the work focused on conceptual-to-preliminary design, consistent with early-stage aircraft design practices used in industry and NASA conceptual studies.

2. Airframe Configuration and External Geometry

As shown in Figure 1, the UAV adopts a conventional fixed-wing configuration comprising a streamlined fuselage, mid-mounted wings, twin vertical stabilisers, and tricycle landing gear. This configuration was selected to prioritise passive stability and endurance, rather than aggressive manoeuvrability.

The fuselage geometry maintains smooth longitudinal transitions to minimise pressure drag while preserving sufficient internal volume. Wing placement was chosen to balance lift distribution and structural integration at the fuselage interface. The twin-fin arrangement increases directional stability and provides yaw control redundancy, particularly advantageous for autonomous flight regimes.

From a first-order aerodynamic standpoint, the aircraft was sized such that steady-level flight satisfies the lift equilibrium condition:

This approach is consistent with preliminary sizing methodologies outlined in NASA and classical aircraft design literature [1], [5].

3. Internal Layout and Subsystem Integration

The internal wireframe view in Figure 2 illustrates that internal architecture was treated as a primary design driver. Major subsystems were positioned to maintain a stable centre of gravity across expected operating conditions.

Key integration decisions include:

• Longitudinal alignment of energy storage near the aircraft CG
• Centralised avionics placement to minimise CG migration and wiring complexity
• Separation of propulsion, avionics, and payload zones to reduce interference and vibration coupling

This internal arrangement supports static longitudinal stability while improving serviceability and future upgrade flexibility. The design ensures the centre of gravity remains forward of the aerodynamic centre, satisfying the classical stability requirement:

as discussed in NASA stability and control guidance [1], [7].

4. Structural Intent and Load Awareness

The external and sectional views shown in Figures 1 and 3 reflect structural intent rather than cosmetic surfacing. The geometry favours planar and gently curved surfaces that can realistically support internal ribs, spars, and longerons.

Wing root geometry and landing gear interfaces were modelled with awareness of load transmission during take-off, landing, and manoeuvring. Landing gear placement acknowledges impact loads and ground handling forces, avoiding unrealistic or visually driven attachment points.

This approach aligns with NASA guidance on light aircraft and UAV structural design, where manufacturability, inspection access, and load paths are treated as first-order considerations [4].

5. Stability and Control Considerations

Directional stability is enhanced through the use of twin vertical stabilisers, increasing yaw damping while allowing smaller individual fin areas. This reduces structural penalties compared to a single large fin while maintaining control authority.

Tail volume and moment arms were selected to provide sufficient pitch and yaw control without excessive wetted area or drag. Control surface sizing follows conventional fixed-wing UAV practices, balancing responsiveness and stability for autonomous operation.

These considerations are consistent with classical flight-dynamics principles and NASA stability analyses for subsonic aircraft [1], [7].

6. Engineering Outcome

This project demonstrates my ability to:

• Translate flight-physics requirements into physical airframe geometry
• Design UAV structures around internal systems rather than external form alone
• Integrate aerodynamic intent, stability, and manufacturability at the conceptual stage
• Produce CAD models that reflect buildable, flight-ready architectures

The result is a UAV concept that prioritises engineering coherence over visual complexity, reflecting a systems-level design mindset applicable to real-world aerospace development.