Definition
The resistance to rotation that exists between a rotating shaft and the bearing supporting it. Bearing friction produces heat, consumes power, and increases with load, speed, and inadequate lubrication.
Plain English
The drag created where a spinning shaft meets the part holding it in place. Even good bearings create some drag, and that drag turns into heat and lost energy.
Context Anchor
Seen in aircraft maintenance, instrument operation, and troubleshooting when a moving part or indicator is stiff, slow, or sticking.
Derivation
A bearing is the part that 'bears' or supports a rotating shaft, allowing it to spin while holding it in position. Friction is the resistance between two surfaces in contact. Together, the term describes the unavoidable drag where these supporting surfaces meet a moving shaft.
Why Pilots Care
Excessive bearing friction increases wear, generates heat, raises fuel consumption, and can lead to component failure if left unchecked.
Analogy
It is like a wheel on a small cart that does not spin freely because its axle is dirty or too tight. The wheel can still turn, but it takes extra force and may not move smoothly.
Intuition Check
Bearing does not mean compass direction here. Here it means the support that a rotating or moving part rides in.
Example Sentence 1
Proper lubrication keeps bearing friction low and prevents the engine from overheating.
Example Sentence 2
The mechanic replaced the wheel bearings after noting increased bearing friction during a taxi test.