Module 5
Mission Definition
Configuration: Quadrotor VTOL
Payload mass W = 1.2 kg
Hover time t = 25 min = 0.417 hr
Design safety margin
Sea-level operation
Battery type: Li-Po
Hover T/W = 2.0 (safe VTOL design)
Initial MTOW Assumption
MTOW = Wpayload + Wbattery+avionics + Wstructural
MTOW ≈ Wpayload /[1 − (βbattery+avionics + βstructural)]
Where represents the weight fraction of those components (typically 0.3 for battery and 0.25 for structure in Li-Po VTOLs).
VTOL MTOW Calculator
VTOL MTOW Calculator
Estimated MTOW:
8.50 kg
Drone Aerodynamic Calculator and Live Graphs
Lift Calculator
Drag Calculator
Typical Mission Parameters
Payload mass (e.g., camera, sensors): 0.4–2 kg
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
Environment: Day/Night, Wind tolerance
Conceptual Design
Initial configuration selection.
High-wing → Stability, surveillance missions
Low-wing → High speed, aerobatic UAVs
T-tail / Conventional tail / V-tail
Tractor vs Pusher propulsion
Recommended for surveillance: High-wing, tractor propeller, conventional tail
Weight Estimation
The total take-off weight of a fixed-wing UAV is determined through an iterative estimation process, as several components depend on each other during the design phase. The overall weight (MTOW) is expressed as the sum of the structural weight, propulsion system weight, avionics weight, payload weight, and battery weight.
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Materials and Structural Design
The selection of materials for the fixed-wing UAV is based on achieving an optimal balance between strength, stiffness, weight, and manufacturability. The wing structure is typically constructed using balsa wood reinforced with a carbon fiber spar, providing adequate bending strength while maintaining low weight. The fuselage is commonly fabricated from EPO foam or fiberglass, which offers good impact resistance and ease of integration for onboard components. A carbon fiber tube is used as the primary spar due to its high strength-to-weight ratio and excellent fatigue resistance. The outer skin of the aircraft is covered using Oracover film or foam, which enhances aerodynamic smoothness and provides environmental protection.
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RC aircraft fabrication
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.
For your Practice!
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.
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.
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.
- 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.
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.
- 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.
- 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.
- 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.
| 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 |