Module 5
VTOL UAV
Fixed Wing UAV
Fabrication of RC Aircraft
AI-Based UAV Airframe Selector
References
VTOL UAV
Quadrotor VTOL Mission Definition
This section presents the initial mission definition and first-level sizing assumptions for a quadrotor VTOL UAV designed for safe hovering operation at sea level using a Li-Po battery system.
Mission Inputs
| Parameter | Selected Value |
|---|---|
| Configuration | Quadrotor VTOL |
| Payload Mass (Wpayload) | 1.2 kg |
| Hover Time (t) | 25 min = 0.417 hr |
| Battery Type | Li-Po |
| Operating Condition | Sea-Level Operation |
| Design Margin | Safety Margin Included |
| Hover Thrust-to-Weight Ratio (T/W) | 2.0 (Safe VTOL Design) |
Design Interpretation
The selected configuration is a quadrotor vertical take-off and landing (VTOL) UAV, intended to carry a 1.2 kg payload while maintaining a hover endurance of 25 minutes. Since the vehicle is expected to operate at sea level, the standard atmospheric density assumption can be used during early sizing calculations.
A hover thrust-to-weight ratio of 2.0 is selected to ensure a safe and controllable VTOL platform. This means the total available thrust should be approximately twice the aircraft weight, which provides:
A hover thrust-to-weight ratio of 2.0 is selected to ensure a safe and controllable VTOL platform. This means the total available thrust should be approximately twice the aircraft weight, which provides:
- Improved take-off reliability
- Better maneuverability
- Reserve thrust for disturbances
- Safer hover and climb performance
Initial MTOW Assumption
The Maximum Take-Off Weight (MTOW) is estimated using the relation:
MTOW = Wpayload + Wbattery+avionics + Wstructural
For preliminary conceptual design, this can be rewritten using component weight fractions as: MTOW ≈ Wpayload / [1 − (βbattery+avionics + βstructural)]
where: - Wpayload = payload mass
- βbattery+avionics = battery + avionics weight fraction
- βstructural = structural weight fraction
Weight Fraction Assumptions
For a typical Li-Po powered VTOL UAV, the following initial fractions are commonly assumed during early-stage sizing:
Therefore,
| Component Group | Typical Fraction |
|---|---|
| Battery + Avionics | 0.30 |
| Structure | 0.25 |
βbattery+avionics + βstructural = 0.30 + 0.25 = 0.55
Preliminary MTOW Calculation
Substituting the values into the MTOW relation:
MTOW ≈ 1.2 / [1 − (0.30 + 0.25)]
MTOW ≈ 1.2 / (1 − 0.55)
MTOW ≈ 1.2 / 0.45 = 2.67 kg
Hence, the initial estimated MTOW for this quadrotor VTOL is: Estimated MTOW ≈ 2.67 kg
Design Insight
This estimated 2.67 kg MTOW becomes the starting point for further subsystem sizing, including:
- Motor selection
- ESC rating
- Propeller diameter and pitch
- Battery capacity estimation
- Frame and structural sizing
Total Required Thrust ≈ 2 × MTOW = 2 × 2.67 = 5.34 kg thrust
For a quadrotor, thrust per motor becomes: Thrust per Motor ≈ 5.34 / 4 = 1.335 kg thrust per motor
This gives a practical target for selecting the propulsion system. VTOL MTOW Calculator
Estimated MTOW:
8.50 kg
Drone Lift & Drag Calculator
Lift Calculator
Drag Calculator
Fixed Wing UAV
Typical Mission Parameters
| Parameter | Typical Range / Description |
|---|---|
| Payload Mass | 0.4 – 2 kg (camera, sensors, mission equipment) |
| Endurance | 1 – 6 hours |
| Range | 20 – 300 km |
| Cruise Speed | 15 – 35 m/s |
| Operating Altitude | 300 – 3000 m |
| Take-off & Landing | Hand-launch / Runway / Catapult |
| Operating Environment | Day / Night, with required wind tolerance |
Conceptual Design
The conceptual design phase begins with the initial selection of aircraft configuration based on mission requirements such as endurance, payload capacity, stability, speed, and operational environment.
Wing Configuration:
Wing Configuration:
- High-wing: Preferred for stability, surveillance, mapping, and long-endurance missions.
- Low-wing: Preferred for higher speed, agility, and aerobatic UAV applications.
- T-tail
- Conventional tail
- V-tail
- Tractor configuration: Propeller mounted at the front.
- Pusher configuration: Propeller mounted at the rear.
Recommended for Surveillance Missions:
High-wing + Tractor Propeller + Conventional Tail
This combination is commonly recommended because it offers: High-wing + Tractor Propeller + Conventional Tail
- Good inherent stability
- Improved low-speed handling
- Clear forward airflow over the wing and control surfaces
- Practical integration for sensors and payloads
Weight Estimation
The total take-off weight of a fixed-wing UAV is determined through an iterative estimation process, because several subsystem weights depend on one another during the early design phase.
The overall Maximum Take-Off Weight (MTOW) is expressed as the sum of the following major components:
The overall Maximum Take-Off Weight (MTOW) is expressed as the sum of the following major components:
MTOW = Wstructure + Wpropulsion + Wavionics + Wpayload + Wbattery
where: - Wstructure = structural weight
- Wpropulsion = motor, ESC, propeller, and associated propulsion hardware
- Wavionics = flight controller, GPS, telemetry, wiring, and electronics
- Wpayload = mission equipment such as camera or sensors
- Wbattery = energy storage system
Materials and Structural Design
The selection of materials for a fixed-wing UAV is based on achieving an optimal balance between:
Overall, the structural design should ensure that the aircraft remains:
- Strength
- Stiffness
- Low weight
- Ease of manufacturing
| Component | Typical Material | Reason for Selection |
|---|---|---|
| Wing Structure | Balsa Wood + Carbon Fiber Spar | Provides low weight with adequate bending strength |
| Fuselage | EPO Foam / Fiberglass | Offers impact resistance and ease of component integration |
| Main Spar | Carbon Fiber Tube | High strength-to-weight ratio and good fatigue resistance |
| Outer Skin / Covering | Oracover Film / Foam Surface | Improves aerodynamic smoothness and protects the structure |
Overall, the structural design should ensure that the aircraft remains:
- Lightweight for longer endurance
- Strong enough to withstand aerodynamic and landing loads
- Easy to assemble, repair, and maintain
Fabrication of RC Aircraft
RC Aircraft & Drone Workshop Series – Key Learning Insights
Workshop Session 1
Key Discussion Highlights
- 4:36 • 25:07 • 27:03Electrical Assembly & Testing The instructor demonstrates how to check electrical continuity using a multimeter, explains the role of the ESC (Electronic Speed Controller), and highlights the importance of matching motor wiring correctly to achieve the desired rotational direction. Safety practices such as heat shrink insulation are also emphasized.
- 9:40 • 34:36 • 1:46:12Motor & Propeller Basics A detailed explanation is given on brushless motors, including how they function in RC aircraft and drones. The workshop also covers the meaning of KV ratings, how to estimate RPM based on battery voltage, and why the motor mount must be firmly secured to reduce vibration and improve flight stability.
- 11:33 – 20:53Regulatory Guidelines (DGCA – India) A significant portion of the session explains DGCA drone regulations in India, including how to identify Red Zones near airports and government installations, the operational limits of Visual Line of Sight (VLOS), and the importance of using the Digital Sky platform for drone registration and compliance.
- 1:10:15 • 1:26:23Construction Techniques The team demonstrates practical assembly steps such as mounting servos, making soldered electrical connections, and selecting suitable materials during construction. The instructor also explains the difference between using CA glue for standard builds and epoxy for foam or delicate materials, helping learners understand structural and material compatibility.
Suggested Related Workshop
Recommended for Further Learning
Advanced UAV / RC Aircraft Practical Session
This workshop is recommended as a follow-up learning resource for students who want to strengthen their understanding of UAV electronics, propulsion systems, RC aircraft assembly, practical testing, and hands-on integration.
It complements the previous session well and is suitable for both beginners and intermediate learners who wish to deepen their practical exposure in UAV and RC aircraft systems.
Credits
Workshop Venue: GNA University – Aerospace Department
Workshop Theme: RC Aircraft and UAV Practical Learning Sessions
Purpose: To support student learning in drone electronics, aircraft assembly, propulsion systems, DGCA awareness, and practical hands-on UAV education.
Acknowledgment
We sincerely acknowledge the Aerospace Department of GNA University for providing the academic environment, infrastructure, and support for conducting and recording these practical workshop sessions.
Special appreciation is extended to the faculty members, technical mentors, workshop coordinators, and participating students whose involvement contributed to making these sessions meaningful and educational.
These videos serve as a valuable learning resource for students interested in UAV systems, RC aircraft design, drone electronics, and hands-on aerospace skill development.
Systematic UAV Motor Performance Troubleshooting Guide
Drone motors are critical components of the UAV propulsion system. Abnormal motor behavior such as unstable hovering, excessive vibration, flipping during takeoff, or sudden power loss usually indicates issues within the propulsion system, sensors, or control electronics. This guide provides a structured troubleshooting procedure to help pilots identify and resolve motor-related faults systematically.
⚠ Safety Warning: Always remove propellers before performing electrical checks or motor tests to prevent serious injury.
Step 1: Initial Visual and Acoustic Inspection
Before disassembling the drone, begin with basic observation and listening tests.
- Check for broken or cracked propellers.
- Inspect motor mounts and screws for looseness.
- Listen for grinding or unusual sounds during motor startup.
- Look for loose wiring between motors and ESCs.
These quick checks can immediately identify many common UAV motor faults.
Step 2: Motor Not Responding or ESC Beeping
If a motor fails to spin and the ESC emits continuous beeping, the issue is often related to signal or power transmission.
- Check Motor-ESC Connections: Ensure the three-phase motor wires are securely connected or soldered.
- ESC Throttle Calibration: Calibrate the ESC throttle range so that it correctly identifies minimum and maximum throttle positions.
- Verify Flight Controller Configuration: Ensure motor numbering and ESC protocol (PWM, OneShot, DShot) match the configuration in the flight controller software.
Step 3: Motor Rotation Abnormalities
- Excessive vibration: Check propeller balance and inspect propellers for damage.
- Motor speed instability: May indicate mechanical damage or electrical faults.
- Internal motor inspection: Rotate the motor manually. If resistance or roughness is felt, the bearings, magnets, or internal windings may be damaged.
- Electrical winding test: Use a multimeter to measure resistance between motor phases to detect open circuits or short circuits.
Step 4: Drone Flipping During Takeoff
Flipping during takeoff is usually caused by incorrect motor rotation direction or propeller installation.
- Confirm each motor rotates in the correct direction.
- Install CW propellers on clockwise motors.
- Install CCW propellers on counterclockwise motors.
- Recalibrate the flight controller accelerometer using six-axis calibration.
Step 5: Power and Payload Compatibility
- Battery Voltage Mismatch: Ensure battery cell count matches motor and ESC requirements.
- Oversized Propellers: Large propellers increase current draw and may overload motors.
- Excess Payload Weight: Total aircraft weight must remain below the propulsion system's maximum thrust capability.
- Motor Overheating: After flight, check motor temperature. A significantly hotter motor may indicate internal friction or overload.
Step 6: Communication and Signal Interference
- Keep signal wires separated from high-current power cables.
- Use shielded wires or ferrite rings to reduce electromagnetic interference.
- Ensure stable power supply to the flight controller.
- Check telemetry and remote control signal stability.
Step 7: Environmental and Battery Factors
- Low Temperature Lockout: Cold temperatures increase internal battery resistance and reduce power output.
- Battery Aging: Old batteries may show inaccurate charge levels and drop voltage quickly.
- Environmental Interference: High electromagnetic environments may affect sensor readings and motor control signals.
Troubleshooting Summary Table
| Problem | Possible Cause | Recommended Action |
|---|---|---|
| Motor not spinning | Loose ESC wiring | Check and re-solder connections |
| Motor vibration | Unbalanced propeller | Balance or replace propellers |
| Drone flips during takeoff | Incorrect motor direction | Verify motor rotation and propeller placement |
| Low thrust | Battery voltage mismatch | Use compatible battery configuration |
| Motor overheating | Overload or friction | Inspect bearings and reduce payload |
AI-Based UAV Airframe Selector
AI-Based UAV Mission & Airframe Selector
Airframe Knowledge Base
1. Fixed-Wing (Conventional)
Best for long range & high altitude missions.
Pros: Efficient flight, glide capability.
Cons: Requires runway/launcher, cannot hover.
2. Multirotor
Best for complex environments & stationary observation.
Pros: VTOL, high maneuverability.
Cons: Low endurance (<45 mins typical).
3. Flying Wing (Tailless)
Best for stealth & portability.
Pros: Low radar cross-section, durable.
Cons: Pitch instability.
4. VTOL Hybrid
Best for remote logistics.
Pros: VTOL + cruise efficiency.
Cons: High mechanical complexity.
References
Reference
1. S.S. Chin. Missile Configuration Design. McGraw Hill, 1961.
2. Mark Pinney Aerodynamics of Missiles and Rockets. McGraw-Hill Education, 2013.
3. Marvin Hobbs Fundamentals of Rockets, Missiles, and Spacecraft. J.F. Rider, 1962.
4. Sethunathan, P., Sugendran, R. N., & Anbarasan, T. Aerodynamic Configuration design of a missile at Int J Eng Res & Technol (IJERT), 2015.
5. Jack N. Nielsen Missile Aerodynamics. NIELSEN ENGINEERING & RESEARCH, INC, 1988.
6. Siouris, George Missile Guidance and Control Systems. Springer New York, 2006.
2. Mark Pinney Aerodynamics of Missiles and Rockets. McGraw-Hill Education, 2013.
3. Marvin Hobbs Fundamentals of Rockets, Missiles, and Spacecraft. J.F. Rider, 1962.
4. Sethunathan, P., Sugendran, R. N., & Anbarasan, T. Aerodynamic Configuration design of a missile at Int J Eng Res & Technol (IJERT), 2015.
5. Jack N. Nielsen Missile Aerodynamics. NIELSEN ENGINEERING & RESEARCH, INC, 1988.
6. Siouris, George Missile Guidance and Control Systems. Springer New York, 2006.