Definition
On a rotating propeller, the blade that is moving upward through its arc on a given side of the propeller disc at any moment. On a conventional clockwise-rotating propeller (as viewed from the cockpit), the ascending blade is on the left side of the propeller arc, and the descending blade is on the right.
Plain English
As a propeller spins, each blade is moving up on one side of the circle and down on the other. The blade currently moving up is called the ascending blade.
Context Anchor
Seen in multiengine training when explaining minimum control speed and why the loss of one engine can be harder to control than the loss of the other.
Derivation
From Latin ascendere, 'to climb up.' The word simply names the blade that is climbing through its arc, as opposed to the one descending on the other side.
Why Pilots Care
Determines which engine is critical in a twin; the side whose descending blade is farther from centerline produces greater yaw, directly affecting minimum control speed and safe single-engine handling.
Grounding Statement
Picture the spinning propeller as a circle: the ascending blade is the part of that circle moving from low to high.
Intuition Check
Ascending blade does not mean a blade that makes the airplane climb. It means the propeller blade moving upward around the propeller’s circle of rotation.
Example Sentence 1
Because the descending blade produces more thrust than the ascending blade, the right engine's thrust line sits farther from the centerline, making the left engine the critical engine.
Example Sentence 2
When practicing VMC demonstrations the instructor points out that the left engine's ascending blade creates less opposing thrust, making the right engine the critical one.