4.3 Load Factor and Maneuvering
Key Takeaways
- Load factor (G) = Total Lift ÷ Weight. In level flight, load factor is 1G.
- Steeper bank angles dramatically increase load factor: 30° = 1.15G, 45° = 1.41G, 60° = 2G.
- At 2G (60° bank), the structure must support double the aircraft weight and motors need double the power.
- Turbulence creates involuntary load factor changes — reduce speed and weight to increase margins.
- Avoid aggressive maneuvers near max weight — the combination multiplies structural stress.
4.3 Load Factor and Maneuvering
Load factor measures the additional stress placed on an aircraft's structure during maneuvering. While more commonly discussed in the context of manned aircraft, the concept applies to drones and appears on the Part 107 exam.
What Is Load Factor?
Load factor is the ratio of the total aerodynamic load on the aircraft to its actual weight:
Load Factor (G) = Total Lift / Weight
- In straight, level flight: Load factor = 1G (lift equals weight)
- In a banked turn: Load factor increases (must generate more lift to maintain altitude)
- Higher load factor = more stress on the structure
Load Factor in Turns
When a drone banks into a turn, it must generate extra lift to maintain altitude. The steeper the bank angle, the higher the load factor:
| Bank Angle | Load Factor (G) | Extra Lift Needed |
|---|---|---|
| 0° (level) | 1.0G | None |
| 15° | 1.04G | 4% more |
| 30° | 1.15G | 15% more |
| 45° | 1.41G | 41% more |
| 60° | 2.0G | 100% more (double!) |
| 75° | 3.86G | 286% more |
| 90° | Infinite | Impossible to maintain level flight |
Key Concept: At a 60° bank angle, the load factor is 2G — meaning the drone's structure and motors must handle double the aircraft's weight. This is why steep turns at high weight or in thin air can be dangerous.
Load Factor Effects on Drones
Structural stress:
- Motor mounts and arms experience increased force during aggressive maneuvers
- Propeller shafts and bearings are stressed
- Excessive load factor can cause structural failure (arm breakage, propeller departure)
Power requirements:
- Higher load factor requires more thrust to maintain altitude
- Battery drain increases significantly during aggressive maneuvering
- A drone at 1.5G needs 50% more power than in level flight
Stall speed (fixed-wing drones):
- Stall speed increases with the square root of the load factor
- At 2G (60° bank), stall speed increases by 41%
- This means a fixed-wing drone needs more airspeed to maintain lift in steep turns
Turbulence and Load Factor
Turbulence creates sudden, involuntary changes in load factor:
- A strong updraft hitting the drone increases the load factor momentarily
- A strong downdraft decreases it (potentially to negative G — momentary unloading)
- Gusts can cause rapid oscillations in load factor
- Operating a heavily loaded drone in turbulence compounds the structural stress
Practical Implications for Part 107
- Avoid aggressive maneuvers at maximum weight — the structure has less margin
- Reduce speed in turbulence — slower speed reduces the load factor from gusts
- Do not make steep banked turns at low altitude — if a motor fails mid-turn, recovery requires altitude
- Check manufacturer G-limits — most consumer drones are not rated for high-G maneuvers
- Weight and G-load are multiplicative — a 5-pound drone at 2G experiences forces as if it weighs 10 pounds
At a 60° bank angle, the load factor on an aircraft is approximately:
As bank angle increases during a turn, what happens to the load factor?