What this sheet works out
Efficiency against airspeed
How these are worked out — the equations behind this sheet, their sources, and what each one assumes.
The propeller at each condition
Where people go wrong
The errors this method actually invites, and what it does about each. Every one of them is already a warning somewhere — in a note that appears when your own figures trip it, in the scope statement, or in the equations behind the page. Collected here so you can read them before you need them.
Comparing static thrust with the thrust in flight. They come from different models on purpose. At zero advance the blade is stalled and the disc model runs well over, so static uses a figure of merit instead: 1,391 g against the 1,887 g the disc model claims for the same propeller.
Asking for thrust past the pitch speed. Actuator-disc theory knows nothing about pitch and will promise thrust at any speed. A real fixed-pitch propeller stops pulling as it runs out of angle, which is why slip is reported beside the answer and everything past 80% of pitch speed is shaded.
Using the unloaded RPM. Kv times pack voltage is what the motor does with nothing attached. Against a propeller it is 80 to 85% of that, and the pack sags under the current on top — so even the loaded figure here is the optimistic one.
Treating efficiency as a property of the propeller. It is a property of the operating point. The same propeller pushing hard at low speed throws air backwards fast and loses the kinetic energy in the wake; cruising gently it throws it back slowly and wastes much less.
Expecting it to know the blade. Disc theory works from disc area alone. Planform, aerofoil, twist and model Reynolds numbers are all outside it, and measured data from the propeller's maker beats every figure on this page.