This calculator estimates the thrust of a coaxial counter-rotating propeller pair versus a single propeller at the same total power, using a simple actuator-disk/momentum-theory model.
It lets you adjust diameter, air density, power split, and wake interaction factor to see thrust values, induced velocities, and performance ratios in real time.
Coaxial vs Single Prop Thrust (Hover)
Momentum-theory estimate with a lower-rotor interaction factor c. Fully scoped: won’t affect your theme.
Inputs
kg/m³
m
W
–
What is the interaction factor c?
Lower rotor inflow model:
w = c·vu, where vu = (Pu/(2ρA))^{1/3}. Tight spacing (~0.15–0.4 D): try 1.2–1.4.Results
Single prop thrust (Ptot)
–
Actuator-disk ideal
Coax total thrust
–
Upper + Lower
Upper rotor thrust
–
vu = – m/s
Lower rotor thrust
–
vl = – m/s
Thrust ratio (coax/single)
–
Δ = –
Downwash at lower disk
–
w = c·vu
Outputs in N. For kgf, divide by 9.80665.
Model equations
Single:
T = (2ρA)^{1/3} P^{2/3}. Upper: v_u = (P_u/(2ρA))^{1/3}, T_u=2ρA v_u^2.
Lower: solve P_l = 2ρA v_l (w+v_l)^2, then T_l=2ρA v_l (w+v_l).