Disc loading is the ratio of a rotary-wing aircraft’s weight to the total area swept by its rotors. For a quadcopter with four propellers of diameter d:
disc loading = W / (4 × π × (d/2)²)
Disc loading is the rotary-wing analog of wing loading — it governs the fundamental performance trade-offs for hovering and vertical flight:
Low disc loading (large rotors relative to weight):
- More efficient hover (less power required per unit weight)
- Lower downwash velocity (less ground disturbance, safer for nearby people)
- Quieter (lower tip speeds for a given thrust)
- Larger physical footprint
High disc loading (small rotors relative to weight):
- Less efficient hover (more power, shorter flight time)
- Compact airframe (fits through doorways, deploys from small containers)
- Faster forward flight (less rotor drag)
- Noisier
Representative disc loading values:
| Platform | Disc loading (kg/m²) | Notes |
|---|---|---|
| Large helicopter (UH-60) | 30–45 | Low for efficiency, payload |
| Small UAV helicopter (S-100) | 20–35 | Moderate, endurance-optimized |
| Photography multirotor (DJI Mavic) | 40–70 | Compact form factor |
| Racing quadcopter | 80–150 | Minimum size, maximum agility |
| Ducted-fan micro UAV | 100–200 | Very compact, reduced efficiency from duct |
Disc loading interacts directly with battery sizing for electric multirotors: higher disc loading requires more power to hover, draining the battery faster, reducing endurance. This is why large-diameter, slow-turning propellers are preferred for endurance missions (mapping, inspection) and small, fast-spinning propellers are preferred where compactness matters more than flight time (racing, indoor inspection).
Related terms
- Wing Loading — the fixed-wing equivalent
- Thrust-to-Weight Ratio — the performance parameter that disc loading feeds into
- Propeller Pitch — the blade geometry interacting with disc loading