Definition
The resistance to motion that occurs when two surfaces are in contact and one moves, or tries to move, relative to the other. In aviation maintenance, friction generates heat and wear, which is why moving parts are lubricated, fitted with bearings, or designed with low-friction materials.
Plain English
The drag or rubbing force that slows things down when two surfaces slide against each other. It also produces heat, which is why machines get hot and parts wear out over time.
Context Anchor
Seen in aircraft maintenance when discussing moving parts, brakes, tires, bearings, controls, and lubrication.
Derivation
From the Latin fricare, meaning 'to rub.' The original sense — rubbing — is exactly what friction does at a surface level, which makes the technical meaning easy to hold onto.
Why Pilots Care
Friction in the wrong place causes wear, heat, and component failure. Friction in the right place — brakes, clutches, tire-to-runway contact — is what makes the aircraft controllable. Maintenance work is largely about managing friction: reducing it where it harms, preserving it where it helps.
Grounding Statement
You can feel friction when you push your hand across a table and the surface resists the movement.
Intuition Check
Friction does not always mean something is wrong. In aircraft, the right amount of friction can be useful, but too much or too little can create a maintenance or safety problem.
Example Sentence 1
The technician applied grease to the hinge to reduce friction and prevent premature wear.
Example Sentence 2
Skin friction along the wings adds to total aerodynamic drag during flight.