Definition
A change in the timing relationship between two alternating current (AC) signals of the same frequency, measured in degrees, where one waveform leads or lags the other rather than peaking at the same instant.
Plain English
Two electrical signals are doing the same up-and-down cycle, but one is slightly ahead or behind the other in time. Phase shift is the size of that timing offset.
Context Anchor
Seen in aircraft electrical, radio, antenna, and instrument-system discussions where alternating electrical signals are compared.
Derivation
From Greek 'phasis' meaning 'appearance' or 'stage of a cycle,' combined with 'shift' meaning a change in position. In electronics, 'phase' refers to where a signal is within its cycle, so a phase shift is a movement of that timing point relative to another signal.
Why Pilots Care
Uncorrected phase shifts in alternator or generator output can reduce charging efficiency and affect instrument accuracy.
Analogy
Think of two runners on the same circular track running at the same speed. If one is always a quarter-lap behind the other, that gap is the phase shift — same pace, different point in the cycle.
Intuition Check
Phase shift does not mean a phase of flight has changed. Here, it means a timing offset between repeating electrical signals.
Example Sentence 1
A phase shift between the reference and signal inputs of the synchro caused the heading indicator to display an incorrect bearing.
Example Sentence 2
A phase shift in the audio circuit produced static in the pilot's headset.