Definition
In aircraft propeller terminology, the back of a propeller blade is the cambered (curved) side that faces aft, away from the direction of flight. It is the surface that produces lower pressure as the blade moves through the air, analogous to the upper surface of a wing.
Plain English
The back of a propeller blade is the curved side that faces backward — toward the tail of the airplane — when the propeller is installed and turning.
Context Anchor
Seen in propeller inspection, repair, and blade-shape descriptions in powerplant maintenance material.
Derivation
Back comes from the ordinary English word for the rear or opposite side of something. In propeller use, it names one side of the blade, but it does not simply mean the rear of the airplane or the rear-facing side.
Why Pilots Care
Knowing which side is the back matters during preflight and maintenance inspections. Nicks, gouges, or corrosion on the back of the blade are reported and dressed differently than damage on the face, and confusing the two can lead to incorrect repairs.
Analogy
Think of a propeller blade as a small wing rotated to slice through the air. The back of the blade is like the top of a wing — curved and on the low-pressure side.
Intuition Check
Do not assume back means the aft-facing side of the aircraft. Here, back means the curved side of the propeller blade, opposite the blade face.
Example Sentence 1
During the preflight inspection, the technician ran a finger along the back of each propeller blade to check for nicks and corrosion.
Example Sentence 2
Install the gasket so the smooth side faces the back of the accessory case.