Propellers

🟢 Start — zero knowledge, plain words. 🟡 Hands-on — building or buying, specifics and tradeoffs. 🔴 Specialist — the physics and math behind it.

🟢 Start. The propeller converts rotation into thrust — it's the only part of the drone that touches the air. Read 5×4.3×3 as: 5″ diameter, 4.3″ pitch, 3 blades. Pitch is the theoretical distance the prop "screws itself" through the air per revolution — like a bolt thread: fine thread = precision and force, coarse = speed.

🟡 Hands-on. Higher pitch buys top speed and "grip" in fast maneuvers, but loads the motor and battery; lower pitch buys efficiency and smooth hover. Three blades are the freestyle compromise (traction, quieter); two blades win long range (peak efficiency). Material: polycarbonate forgives crashes — and a damaged prop goes in the bin immediately, because one cracked blade produces vibration that torments the entire electronics stack. Bigger/steeper prop = more current: check the motor maker's thrust tables.

🔴 Specialist. Prop performance follows scaling laws (n ≡ rev/s, D ≡ diameter):

$$T = C_T\,\rho\,n^2 D^4,\qquad P = C_P\,\rho\,n^3 D^5$$

Thrust grows with the square, power with the cube of RPM — the fundamental reason big slow props beat small fast ones on efficiency. Momentum theory sets the hover-power floor: for a 750 g five-inch ($T = 7.36$ N) with total disk area $A = 4\pi(0.0635)^2 \approx 0.051$ m²:

$$P_{\text{ideal}} = \frac{T^{3/2}}{\sqrt{2\rho A}} \approx 57\ \text{W} \;\Rightarrow\; P_{\text{electrical}} \approx \frac{57}{0.55} \approx 103\ \text{W} \approx 4.6\ \text{A on 6S}$$

— exactly the hover current you'll see in the OSD. Also watch blade tip speed ($v = \pi D n$): approaching ~0.6 Mach means a steep rise in noise and losses.

🖼️ Photos: your own 2- vs 3-blade comparison; NASA (public domain) propeller-vortex visualizations.