Aviation Calcs

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Propeller Static Thrust Calculator

At zero forward speed, momentum theory gives a simple link between shaft power, disk area, and thrust: T = (2 ρ A P²)¹/³. Enter a power and a diameter (or area), optionally a static efficiency or figure of merit, and this page returns that ideal static thrust and the induced velocity. It is a static estimate, not a cruise thrust, and not the advance-ratio calculation on the propeller-advance-ratio page.

Power defaults to kilowatts; a “useful” efficiency of 1.0 is the ideal disk. Values of 0.6–0.8 are more realistic for a static propeller or fan.

Result

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T = (2 ρ A P²)¹/³ at zero flight speed

The actuator disk at rest has an induced velocity vi = √(T / (2 ρ A)) and a power P = T vi. Solving for thrust gives T = (2 ρ A P²)¹/³. A 100 kW engine on a 2-metre propeller, in ISA sea-level air and with ideal efficiency, produces about 4,260 N (around 960 lbf) of static thrust, with vi = P/T. If you enter an efficiency or static figure of merit η, the page uses η Pshaft as the useful power, and thrust scales as η2/3.

As soon as the airplane starts to move, the inflow changes and this static formula no longer holds. For advance ratio, rotational tip speed, and helical tip Mach in forward flight, use the propeller advance ratio calculator. For a hovering helicopter rotor and a hover ceiling, use hover power.

Sources

Frequently asked questions

Why is this less than a static-thrust stand measurement?

Or more, depending on η. The ideal disk ignores swirl, tip losses, and a nacelle. A measured static thrust will not match η = 1.

Can I use this at cruise?

No. It is a V = 0 formula. Cruise thrust needs an advance ratio and a propeller map or a blade-element model.

How is this different from the advance-ratio calculator?

That page computes J = V/(nD) and tip Mach in forward flight. This one estimates static thrust from power and area.