Squawk Codes Explained: 1200, 7500, 7600 And 7700

When a controller says “Cessna Three Alpha Bravo, squawk four two seven one,” the pilot dials 4271 into the transponder and reads it back. The radar screen then shows that airplane with a data tag: call sign, altitude and ground speed. That is the whole meaning of squawk. The FAA’s Pilot/Controller Glossary defines it as the instruction to activate the transponder and ADS-B Out with altitude reporting on, on the mode or code given.

Squawking, as a verb, is just operating on a code. “We’re squawking 1200” means the airplane is VFR and not talking to ATC. “Squawk VFR” is a controller telling you to go back to 1200 when radar service ends. “Squawk ident” means press the IDENT button once, which makes your target bloom on the controller’s screen for a few seconds so they can pick you out of the traffic.

Each code is four digits, and each digit runs from 0 to 7, because transponder codes are octal. There is no 8 or 9 on the knob. That gives 4,096 possible codes, which is where the phrase “Mode A 4096-code capability” in 14 CFR 91.215(b) comes from. A handful are reserved, and those are the ones to know cold.

Squawk 7700 means the aircraft has an emergency. AIM 6-2-2 tells a pilot in distress or urgency who is not already in radar contact and on a discrete code to set 7700. The code triggers an alarm at every facility that can see the target, which matters if you are on the wrong frequency, or no frequency at all. If you are already talking to a controller on an assigned code, the AIM says you may stay on that code.

Declaring an emergency gives you authority under 14 CFR 91.3(b) to deviate from any rule in Part 91 to the extent the emergency requires. Pilots wait too long to use it. Under 91.3(c) a written report is due only if the FAA asks for one.

Squawk 7600 means two-way radio communication has failed. ATC sees the code and expects you to follow the lost-communication procedure. For an IFR flight that is 14 CFR 91.185, which sets the route and altitude to fly. For a VFR pilot in visual conditions it is simpler: 91.185(b) says continue VFR and land as soon as practicable.

At a towered field like Van Nuys, a radio failure ends with light gun signals from the tower. We cover the full light-signal table on the Class D Airspace page. Before you squawk 7600, check the obvious things: volume, the frequency itself, the headset jack and the audio panel.

Squawk 7500 means the aircraft is being hijacked or is under unlawful interference. Only the nondiscrete code 7500 is decoded as a hijack, and it brings a response from far beyond air traffic control. It is the code you must never set by mistake.

AIM 4-1-20 asks pilots to have the transponder and ADS-B Out transmitting, with altitude reporting, any time the aircraft is on the airport movement area, including taxiways and runways. At the parking spot you go to standby or off.

In the air the rule is in 14 CFR 91.215(c): if your aircraft has an operable transponder, you must operate it, including Mode C if installed, in all controlled airspace and in the airspace listed in 91.215(b). In Los Angeles that means the switch lives in ALT. If ATC says “stop altitude squawk,” your encoder may be giving a wrong altitude; set ON, not off.

Van Nuys Airport is about 16.5 nautical miles north of LAX in a straight line, well inside the 30-mile Mode C veil described in 14 CFR 91.215(b)(2). The field is Class D Under The Los Angeles Class B Shelf, and the tower expects your transponder in ALT before you taxi.

Ask for flight following, and SoCal Approach, the TRACON that works the Los Angeles basin, will assign you a discrete code. You will hear “radar contact,” which is not a Class B clearance. Only the words “cleared into the Class Bravo” let you in, as the Airspace Classes Explained guide sets out. Burbank’s Class C Airspace is the nearest place where the transponder is required by the class itself.

Squawk codes come up on the written and in the oral. Expect them on the FAA Written Exam, and expect an examiner to ask what you would set for a radio failure on the Private Pilot Checkride. Radio phraseology starts with the Pilot Phonetic Alphabet; numbers are spoken digit by digit, so 4271 is “four two seven one,” never “forty-two seventy-one.”