Definition
A particular stage or point in a recurring cycle, used to describe the timing relationship between two waveforms or alternating quantities. Two signals are 'in phase' when their peaks and troughs occur at the same moments, and 'out of phase' when they do not. Phase is measured in degrees, with one full cycle equaling 360°.
Plain English
Where you are within a repeating cycle. If two repeating things rise and fall together, they are in step; if one is ahead of or behind the other, they are out of step.
Context Anchor
Seen in aircraft electrical system discussions, especially with alternating current, generators, and signal timing.
Derivation
From the Greek 'phasis,' meaning 'appearance' or 'aspect,' originally used to describe the changing appearance of the moon through its cycle. The same idea carries into aviation electronics: where something is within its repeating cycle.
Why Pilots Care
Phase relationships matter in AC electrical systems, instrument synchros, and radio navigation equipment like VOR, where the position of an aircraft is determined by comparing the phase of two signals.
Analogy
Think of two people walking in step. If their feet hit the ground at the same time, they are in phase. If one person’s step is half a step behind, they are out of phase.
Intuition Check
Phase does not just mean a general stage, like “phase of training.” In electrical and wave discussions, it means position or timing within a repeating cycle.
Example Sentence 1
The VOR receiver determines bearing by comparing the phase difference between the reference and variable signals.
Example Sentence 2
Fuel planning changes depending on whether the aircraft is in the cruise phase or the approach phase.