Definition
The aerodynamic resistance the propeller blades encounter as they rotate through the air, which the engine must overcome to maintain or change rpm. Propeller load increases with higher blade angle, higher airspeed against the blades, denser air, or any condition that forces the blades to take a bigger 'bite' of air per revolution.
Plain English
How hard the air pushes back on the spinning propeller. The harder that push-back, the more work the engine has to do to keep the prop turning at a given speed.
Context Anchor
Seen in takeoff, climb, and cruise discussions when explaining why engine speed and power can change as airspeed or propeller setting changes.
Derivation
Propeller comes from the idea of propelling, or driving something forward. Load, in engine use, means the work or resistance placed on the engine, not baggage or cargo weight.
Why Pilots Care
Changes in propeller load alter engine RPM and power absorption, requiring pilots to adjust throttle or pitch to stay within operating limits.
Analogy
Think of pedalling a bicycle. In a low gear the pedals spin easily because each push moves only a little chain — light load. Shift to a high gear and each push must move much more — heavy load, slower cadence unless you push harder. The propeller works the same way: a bigger blade angle is a higher gear.
Grounding Statement
Higher airspeed or coarser blade pitch increases propeller load and lowers RPM for the same throttle setting.
Intuition Check
Do not read load here as cargo weight. Here, load means the resistance or work demand the propeller puts on the engine.
Example Sentence 1
As the airplane accelerated down the runway, the propeller load decreased and the engine rpm rose toward its rated takeoff value.
Example Sentence 2
In cruise the propeller load decreases as airspeed rises, allowing the engine to turn at a higher RPM for the same power.