Definition
A common pilot term for a radio control feature that lets the user pre-tune a standby frequency alongside the active frequency, then swap the two with a single button press. The active frequency becomes standby, and the standby becomes active.
Plain English
A radio function that holds two frequencies at once -- the one you're using and the next one you'll need -- and lets you switch between them with one button.
Context Anchor
Seen in discussions of aircraft electronics, digital equipment, and some avionics systems.
Derivation
Named after the back-and-forth motion of flipping something over and back. The two frequencies trade places each time the button is pressed, just like flipping a coin from one side to the other.
Why Pilots Care
It reduces cockpit workload. A pilot can dial in the next ATC frequency well before the handoff, then swap to it instantly when told to contact the next controller -- no fumbling with numbers during a busy moment.
Analogy
Think of a light switch that can only be up or down. It stays where it is until something moves it to the other position.
Intuition Check
Do not read flip-flop here as a casual change of opinion or a sandal. In aircraft electronics, it means a circuit that holds one of two stable conditions and switches when triggered.
Example Sentence 1
After being told to contact Departure on 124.35, she pre-set it in standby and hit the flip-flop as soon as she was clear of the tower frequency.
Example Sentence 2
Flight computers rely on flip-flops to store binary information for altitude alerts and mode selections.