Definition
A change that occurs in a straight-line, proportional relationship — when one quantity changes, another changes by a constant amount or in fixed steps. In aircraft systems, a linear change means the output rises or falls at a steady, predictable rate as the input varies, with no curves, jumps, or accelerations.
Plain English
Something that changes in a steady, even way. If you double the input, the output doubles. If you triple it, it triples. The relationship is constant and predictable.
Context Anchor
Seen in aircraft maintenance discussions about how materials expand, shrink, fit, or keep proper spacing as conditions change.
Derivation
From the Latin linearis, meaning 'belonging to a line.' A linear change literally plots as a straight line on a graph — same slope from start to finish.
Why Pilots Care
Many aircraft instruments and controls are designed to respond linearly so the pilot or technician can predict behavior. When a system that should be linear stops behaving that way, it usually points to a fault, wear, or calibration problem.
Grounding Statement
A metal panel sitting in hot sun may become very slightly longer than it was in the shade.
Intuition Check
Linear change does not mean a change that happens smoothly or gradually on a graph. Here, linear means the change happens in a straight-line measurement, such as length or width.
Example Sentence 1
The fuel quantity sensor produces a linear change in voltage as the tank level rises, allowing the gauge to read accurately throughout the range.
Example Sentence 2
Technicians measured a linear change in rivet hole diameter after applying constant torque over several test cycles.