Definition
The flat or nearly flat side of a propeller blade that faces aft (toward the pilot) when the propeller is installed on the aircraft. It is the rearward surface of the blade, opposite the curved cambered side that faces forward.
Plain English
On a propeller blade, the face is the back side — the flatter side you see when you stand behind the aircraft and look at the prop.
Context Anchor
Seen in propeller inspection, maintenance descriptions, and blade nomenclature diagrams.
Derivation
From everyday English, where the 'face' of an object is its main flat surface (like the face of a hammer or the face of a clock). On a propeller, the flat side of the blade is called the face for the same reason.
Why Pilots Care
Correct identification of the face is essential for recognizing stress cracks, erosion, and damage that directly affect thrust and safety.
Intuition Check
Do not read face as just “the side you happen to be looking at.” In propeller nomenclature, face names a specific side of the blade: the flatter pressure side.
Example Sentence 1
During the preflight inspection, the technician checked the face of each propeller blade for nicks and gouges.
Example Sentence 2
Damage on the face reduces the blade's ability to push air efficiently and create thrust.