Definition
A propeller effect in which the descending blade produces more thrust than the ascending blade when the aircraft is flown at a high angle of attack, causing the center of thrust to shift to the right of the propeller disc on a conventional engine and yawing the aircraft to the left. Also known as P-factor.
Plain English
When the nose of the aircraft is pitched up, one side of the spinning propeller bites into the air harder than the other side. This uneven pull tugs the aircraft to one side, usually to the left.
Context Anchor
Seen in propeller and powerplant discussions, especially during high-power, nose-up flight such as takeoff and climb.
Derivation
‘Asymmetrical’ comes from the Greek for ‘not the same on both sides.’ ‘Loading’ here refers to the aerodynamic load (force) on the propeller blades. So the name describes exactly what is happening: the two sides of the propeller are not carrying the same load.
Why Pilots Care
It produces a left yaw tendency that must be countered with rudder, especially during takeoff and climb.
Grounding Statement
Picture a propeller in a climb: the air does not meet every blade in exactly the same way, so one side of the spinning propeller does more work.
Intuition Check
Do not read “loading” here as cargo weight or baggage. In this term, it means aerodynamic force on the propeller blades.
Example Sentence 1
On the takeoff roll, the instructor reminded the student to apply right rudder to counter the asymmetrical loading of the propeller.
Example Sentence 2
Climbing at high power and low airspeed increases asymmetrical loading and requires more rudder input.