the configuration of each UAV component, the designer must be fully aware of the function of each component. Each UAV component has inter-relationships with other components and interferes with the functions of other components. The above six components are assumed to be the fundamental components of an air vehicle. However, there are other components in a UAV that are not assumed here as a major one. The roles of those components are described in the later sections whenever they are mentioned. Table 1.4 illustrates a summary of UAV major components and their functions. This table also shows the secondary roles and the major areas of influence of each UAV component. The table also specifies the design requirements that are affected by each component.
Table 1.5 illustrates a summary of configuration alternatives for UAV major components. In this table, various alternatives for wing, horizontal tail, vertical tail, fuselage, engine, landing gear, control surfaces, and automatic control system or autopilot are counted. An autopilot tends to function in three areas of guidance, navigation and control. More details are given in the detail design phase section. For each component, the UAV designer must select one alternative which satisfies the design requirements at an optimal condition. The selection process is based on a trade-off analysis with comparing all pros and cons in conjunction with other components.
Table 1.4: UAV major components and their functions
Table 1.5: UAV major components with design alternatives
| No | Component | Configuration Alternatives |
| 1 | Fuselage | - Geometry: lofting, cross section - Internal arrangement - What to accommodate (e.g., fuel, engine, and landing gear)? |
| 2 | Wing | - Type: swept, tapered, dihedral; - Location: low-wing, mid-wing, high wing, parasol - High lift device: flap, slot, slat - Attachment: cantilever, strut-braced |
| 3 | Horizontal tail | - Type: conventional, T-tail, H-tail, V-tail, inverted V - Installation: fixed, moving, adjustable - Location: aft tail, canard, three surfaces |
| 4 | Vertical tail | Single, twin, three VT, V-tail |
| 5 | Engine | - Type: turbofan, turbojet, turboprop, piston-prop, rocket - Location: (e.g., under fuselage, under wing, beside fuselage) - Number of engines |
| 6 | Landing gear | - Type: fixed, retractable, partially retractable - Location: (e.g., nose, tail, multi) |
| 7 | Control surfaces | Separate vs. all moving tail, reversible vs. irreversible, conventional vs. non-conventional (e.g., elevon, ruddervator) |
| 8 | Autopilot | - UAV: Linear model, nonlinear model - Control subsystem: PID, gain scheduling, optimal, QFT, robust, adaptive, intelligent - Guidance subsystem: Proportional Navigation Guidance, Line Of Sight, Command Guidance, three point, Lead - Navigation subsystem: Inertial navigation (Strap down, stable platform), GPS |
| 9 | Launch and recovery | HTOL, ground launcher, net recovery, belly landing |
In order to facilitate the conceptual design process, Table 1.6 shows the relationship between UAV major components and the design requirements. The third column in Table 1.6 clarifies the UAV component which affected most; or major design parameter by a design requirement. Every design requirement will normally affects more than one component, but we only consider the component that is influenced most. For example, the payload requirement, range and endurance will affect maximum take-off weight, maximum take-off weight, engine selection, fuselage design, and flight cost. The influence of payload weight is different than payload volume. Thus, for optimization purpose, the designer must know exactly payload weight and its volume. On the other hand, if the payload can be divided into smaller pieces, the design constraints by the payload are easier to handle. Furthermore, the other performance parameters (e.g., maximum speed, stall speed, rate of climb, take-off run, ceiling) will affect the wing area and engine power (or thrust).
Table 1.6: Relationship between UAV major components and design requirements
| No | Design Requirements | UAV Component that Affected Most, or Major Design Parameter |
| 1 | Payload (weight) requirements | Maximum take-off weight |
| Payload (volume) requirements | Fuselage | |
| 2 | Performance Requirements (range and endurance) | Maximum take-off weight |
| 3 | Performance requirements (maximum speed, Rate of climb, take-off run, stall speed, ceiling, and turn performance) | Engine; landing gear; and wing |
| 4 | Stability requirements | Horizontal tail and vertical tail |
| 5 | Controllability requirements | Control surfaces (elevator, aileron, rudder), autopilot |
| 6 | Autonomy requirements | Center of gravity, autopilot, ground station |
| 7 | Airworthiness requirements | Minimum requirements, autopilot |
| 8 | Cost requirements | Materials; engine; weight, etc. |
| 9 | Timing requirements | Configuration optimality |
| 10 | Trajectory requirements | Autopilot |
In order to select the best UAV configuration, a trade-off analysis must be established. Many different trade-offs are possible as the UAV design progresses. Decisions must be made regarding the evaluation and selection of appropriate components, subsystems, possible degree of automation, commercial off-the-shelf parts, various maintenance and support policies, and so on. Later in the design cycle, there may be alternative engineering materials, alternative manufacturing processes, alternative factory maintenance plans, alternative logistic support structures, and alternative methods of material phase-out, recycling, and/or disposal.
The UAV designer must first define the problem statement, identify the design criteria or measures against which the various alternative configurations will be evaluated, the evaluation process, acquire the necessary
