Definition
A value that does not change. In engineering, electrical, and mathematical contexts used in aviation maintenance, a constant is a quantity that remains fixed throughout a calculation, process, or operating condition, in contrast to a variable that changes.
Plain English
Something that stays the same. While other things in a system might go up and down, a constant holds steady at one value.
Context Anchor
Seen in maintenance procedures, system checks, charts, and calculations when one condition must stay the same while another is measured or adjusted.
Derivation
From Latin 'constans,' meaning 'standing firm' or 'unchanging.' The image is of something that stands its ground while everything around it moves — which is exactly how a constant behaves in a formula or system.
Why Pilots Care
When troubleshooting or reading technical data, knowing which values are fixed and which can change is essential. Treating a variable as a constant (or the reverse) leads to wrong conclusions about how a system is behaving.
Intuition Check
Constant does not mean “always true in every situation.” Here it means “not changing during the specific time or condition being discussed.”
Example Sentence 1
In Ohm's Law, if resistance is held constant, current rises as voltage rises.
Example Sentence 2
Standard sea level temperature is treated as a constant when calculating density altitude.