The Seven Six Zero Zero Squawk, the Light Gun Signals Every Student Memorizes and Then Forgets, and the Lost Communications Procedure That Gets You Down Safe When the Radio Goes Quiet

When your radio fails at a towered airport, the procedure is straightforward: squawk 7600, fly a predictable path, watch for light gun signals, and acknowledge each one. Most pilots can recite this from ground school. Far fewer have practiced it well enough to execute it calmly when it actually happens.

Why Radios “Fail” (And Why You Should Check the Simple Stuff First)

Radio failure rarely announces itself. There’s no warning light, no smoke. The first sign is usually just silence - you key the mic, make your call, and hear nothing back.

Before assuming a genuine failure, run through the basics. Is the audio panel configured correctly? Is the headset fully seated? Is the volume up? Is the frequency correct? Is the push-to-talk button stuck in transmit - which would mean you’re blocking the frequency every time you try to listen?

Ninety percent of lost comms incidents in training aircraft trace back to a headset connection or audio panel switch. Start with the mundane before escalating.

What to Do When It’s a Real Lost Comms Situation

If you’ve checked everything - both radios, guard frequency (121.5 MHz), and even tried transmitting blind to advise the tower of a possible failure - and still have no response, it’s time to work the procedure.

Set the transponder to 7600. That is the international code for lost communications. Radar facilities watching your airspace will see that code the moment it changes, and they will begin clearing a path for you.

The critical mindset shift: squawking 7600 means you are no longer flying alone. Controllers can see you on radar. They know your situation. Their job becomes getting you down safely. Your job is to fly a predictable path so they can sequence you with other traffic.

Continue navigating to the airport. Join and fly the traffic pattern normally. Make your behavior easy to anticipate.

The Light Gun Signals You Need to Know Cold

The light gun is a high-intensity, narrow-beam directional light aimed directly at your aircraft. It exists at every towered airport and predates radio communication as a standard ATC tool. There are six signals across two contexts - airborne and on the ground.

Airborne signals:

• Steady green - Cleared to land
• Flashing green - Return for landing (not yet cleared, but being brought in)
• Steady red - Give way to other aircraft and continue circling
• Flashing red - Airport unsafe, do not land
• Alternating red and green - Exercise extreme caution

Ground signals:

• Steady green - Cleared for takeoff
• Flashing green - Cleared to taxi
• Steady red - Stop
• Flashing red - Taxi clear of the runway in use
• Flashing white - Return to your starting point on the airport
• Alternating red and green - Exercise extreme caution

The alternating red and green is the one that trips up students on oral exams. It is not a clearance of any kind. It is a warning that something unpredictable is happening in the traffic environment. Your head needs to be on a swivel.

The other common mix-up: flashing green airborne means return for landing; flashing green on the ground means cleared to taxi. These are completely different instructions. Confuse them in a checkride oral and the examiner will dig in.

How to Acknowledge a Light Gun Signal

Receiving a signal isn’t enough - you have to acknowledge it. The tower may be managing multiple aircraft simultaneously and needs confirmation you received the message before sequencing the next one.

During the day: Rock your wings - left, right, back to level. It should be a clear, deliberate oscillation, not a violent bank. If you’re on short final and rocking your wings feels destabilizing, flash your landing lights instead.

At night: Two flashes of the landing lights tells the tower you received the signal and are complying.

After clearing the runway, flash your landing lights again if you’re uncertain what to do next. That signals to the tower that you’re down, off the pavement, and awaiting further instructions.

How to Find the Light Gun When You Need It

The tower cab is the glassed-in room at the top of the tower structure. During the day, sun angle and background glare can make the light harder to spot. At night it’s much easier to find.

The best time to practice this is before you need it. On your next flight into a towered airport, visually locate the tower cab from each leg of the pattern - downwind, base, and final. If you’ve never done this exercise deliberately, you’ll be surprised how long it takes to actually find the light under pressure.

What Happens During a One-Way Radio Failure

If you can hear the tower but they can’t hear you, a good controller will try this: “If you can hear me, squawk ident.” Pressing the ident button causes your target to bloom on their radar scope for several seconds. That’s your yes.

From there, the controller can issue simple binary instructions. Ident for yes, stay silent for no. Some facilities will ask you to key the mic twice for yes and once for no, producing a brief carrier signal they may detect without voice.

Lost comms doesn’t mean you lose the ability to communicate. It means you shift to different channels.

What to Do After You Land

This step gets skipped more than any other. After a lost comms event at a towered airport, contact the facility as soon as practicable - before you tie down the airplane. The phone number is published in the Chart Supplement for that airport (formerly the Airport/Facility Directory). Call and tell them what happened, when it happened, what you squawked, and what signals you received. That closes the loop and lets them clear your transponder code from their scope.

If you have cell service and the tower number during the event itself, calling directly is a legitimate option. Some pilots keep the local tower’s number on a sticky note in the cockpit. That’s not excessive preparation - it’s crew resource management.

What the ACS Expects on the Checkride

The Airman Certification Standards (ACS) covers lost communications under the emergency operations section for private pilot applicants. Examiners want:

• The correct transponder codes: 7600 for lost communications, 7700 for general emergencies
• All light gun signals - airborne and on the ground - without hesitation
• A complete understanding of the procedure: squawk the code, acknowledge signals with wings or lights, fly a predictably, contact ATC after landing

The oral is where most candidates stumble. They know the squawk code. They know most of the light signals. But they forget the acknowledgment, or they mix up flashing green airborne versus flashing green on the ground. Make a flashcard with six signals and two columns. Run through it until the answer comes before you finish reading the question.

Equipment Worth Having

A handheld aviation transceiver is a genuine safety net in any aircraft with aging avionics. Models capable of aviation frequencies are available for under $200. If your panel avionics fail completely, plug your headset into the handheld and you’re back in communication. Keep it charged. Know how to tune it quickly to local frequencies before you need it.

Further Reading

AIM Chapter 6, Section 4 covers lost communications procedures in full detail. The scenarios there are more complete than most ground school materials, and the light gun signal table is the definitive reference. Read it straight through before your checkride.

Key Takeaways

• Squawk 7600 immediately upon confirming a genuine lost comms situation - radar controllers will see it and begin working to get you down
• Check the simple stuff first: headset connection, audio panel, volume, frequency, and push-to-talk button account for the majority of apparent radio failures
• Know all six light gun signals in both airborne and on-ground contexts - especially the difference between flashing green airborne (return for landing) vs. on the ground (cleared to taxi)
• Acknowledge every signal: rock your wings or flash landing lights during the day; flash landing lights at night
• Call the tower by phone after landing to close the loop - the number is in the Chart Supplement for that airport