Definition
A single switch in the cockpit that controls electrical power to the aircraft's avionics equipment — radios, navigation receivers, transponder, GPS, and similar electronic instruments — as a group, isolating them from the main electrical bus until the pilot is ready to power them on.
Plain English
One switch that turns all the electronic flight equipment on or off together, separately from the rest of the airplane's electrical system.
Context Anchor
You will see the avionics master during cockpit checks, preflight setup, engine start, shutdown, and any checklist step that turns airplane electronics on or off.
Derivation
Avionics' comes from 'aviation electronics' — the electronic equipment used in aircraft. 'Master' here means a single control that governs a whole group of devices, the same way a master switch controls the entire electrical system. So 'avionics master' is the one switch that controls all the avionics together.
Why Pilots Care
Turning the avionics master on too early drains the battery; leaving it on during external checks risks damage from power surges or accidental activation of equipment.
Intuition Check
“Master” does not mean expert or instructor here. It means the main control switch for a group of electrical items.
Example Sentence 1
After starting the engine and confirming stable oil pressure, the pilot turned on the avionics master to bring up the radios and transponder.
Example Sentence 2
After engine start the pilot turned on the avionics master and confirmed that the navigation displays initialized normally.