Definition
Setting a transponder to code 7600 to signal to air traffic control that the aircraft has experienced a loss of two-way radio communication. The code causes a distinctive alert on ATC radar displays so controllers know the pilot can no longer be reached by radio.
Plain English
Putting 7600 into the transponder to tell controllers, without using the radio, that the radio is not working.
Context Anchor
Used during lost-communication procedures, especially in instrument flying when air traffic control needs to understand why the aircraft is not answering radio calls.
Derivation
‘Squawk’ comes from World War II identification systems nicknamed ‘Parrot,’ where aircraft were asked to ‘squawk’ a code so ground radar could identify them. In modern use, to squawk a code means to set that number into the transponder so it shows up on ATC radar.
Why Pilots Care
It lets ATC provide separation, routing, and landing clearance without expecting radio calls, reducing the chance of airspace conflicts.
Intuition Check
Do not assume “squawking code 7600” means announcing “7600” over the radio. It means setting 7600 on the transponder so air traffic control can see the radio failure indication.
Example Sentence 1
After losing both radios, the pilot began squawking code 7600 and continued the flight following lost-communication procedures.
Example Sentence 2
Approach control identified the aircraft squawking code 7600 and issued light-gun signals for landing clearance.