FAR Ninety-One Point One Eight Five, the Squawk Seventy-Six Hundred, and the Lost Comms Procedure Every IFR Pilot Needs to Know Before the Radio Dies

FAR 91.185 governs lost two-way radio communications for IFR pilots operating in controlled airspace. It answers three critical questions in sequence: where to go, what altitude to fly, and when to begin the approach. Knowing this regulation cold - before you ever need it - is both an oral exam requirement and a genuine safety skill.

What Should You Do the Moment You Lose Radio Contact?

Squawk 7600 immediately. That is the universal lost communications transponder code. The instant that code appears on a radar display, every controller watching your target knows you cannot communicate. They will begin adjusting traffic around your expected route and protecting the airspace ahead of you.

The transponder code is your voice when your voice is gone. Use it before doing anything else.

Does It Matter Whether You’re in VMC or IMC When Comms Fail?

Yes - FAR 91.185 treats VMC and IMC as two entirely different scenarios, and the distinction determines everything that follows.

If you are in visual meteorological conditions when the radio fails, the regulation requires you to land as soon as practicable. “Practicable” does not mean immediately in the nearest field. It means as soon as is reasonable given your position, aircraft, and available airports. Find the nearest suitable airport, get on the ground, and call ATC. Do not press on to your original destination.

If you are in instrument meteorological conditions, the situation is more complex. You cannot simply divert visually. Other IFR traffic may be in the pattern or on approach at nearby airports, and you have no way to coordinate. This is where the full lost comms procedure applies.

What Route Do You Fly After Losing Radio Contact?

The regulation establishes a priority order for route selection. Work down the list and use the first option that applies to your situation.

1. The route assigned in your last ATC clearance. If you were cleared direct to a fix or given a specific routing, stay on it. Controllers watching your transponder target will use your last cleared route to build a protected corridor ahead of you. If you deviate from that route on your own initiative, you become unknown to the system trying to protect you.

2. The route specified in any radar vector instructions. If you were being vectored when comms failed - for example, “fly heading 270 for vectors to the ILS final” - make your best judgment to intercept that final approach course and fly toward it.

3. A routing ATC told you to expect during the flight. If the controller mentioned an anticipated routing, use that.

4. The route you filed on your flight plan. This is the last resort, in the absence of any of the above.

The underlying principle: fly predictably. Be where ATC expects you to be. Improvising off-route transforms you from a known, manageable target into an unknown hazard.

What Altitude Do You Fly During Lost Comms?

Unlike the route question - where you pick the most specific and recent guidance - the altitude question asks you to fly the highest of three options:

• The minimum IFR altitude for the route segment you’re flying
• The altitude ATC assigned you
• The altitude ATC told you to expect

Example: ATC assigned you 6,000 feet. The minimum enroute altitude for your segment is 8,000 feet. ATC told you to expect 10,000 feet for the enroute portion. You fly 10,000 feet - the highest of the three.

The logic is straightforward. Each of those numbers represents a floor. Flying above all three simultaneously guarantees the maximum terrain and obstacle clearance. In an abnormal situation, conservative altitude choices are always correct.

When Do You Begin Your Approach Without a Clearance?

This is the question that generates the most confusion on oral exams, and it has a precise answer.

Begin your descent and approach at whichever of these two moments arrives first:

The Expect Further Clearance (EFC) time, if ATC gave you one. An EFC time is issued most commonly when you’re holding - it’s the controller’s estimate of when they expect to have clearance for you. If ATC said “expect further clearance at 2345 Zulu,” write it down. If your radio fails, that time governs when you begin the approach.

Your filed estimated time of arrival (ETA), if you were never given an EFC. When your filed ETA arrives, descend and fly the approach.

Write down every EFC time a controller gives you. That habit costs nothing. If your radio fails thirty seconds after receiving an EFC, that note is the most important piece of paper in the cockpit.

ATC is actively protecting a window for your arrival based on your filed ETA and known routing. Arriving early means traffic may not yet be cleared from your path. Arriving late means the window they built may have closed. Your flight plan is not just paperwork - under lost comms, it becomes the timing contract between you and the entire ATC system. File accurate ETAs.

What Light Gun Signals Do You Need to Recognize on Final?

If the destination has an operating control tower, the facility will almost certainly be notified by the time you break out of the clouds. The tower has the light gun ready. Know these signals cold:

A steady green on final is your clearance. Acknowledge in daylight by rocking your wings. At night, flash your landing light.

After landing, acknowledge taxi instructions by flashing your landing or taxi light, or by briefly cycling your wingtip strobes if you are stopped and waiting.

What If You’re Landing at a Non-Towered Airport?

Without an operating control tower, there is no light gun. Make standard traffic pattern entries, broadcast your position on the common traffic advisory frequency (CTAF) even though you cannot hear responses, and treat the landing like any other arrival at a non-towered field.

Other traffic in the pattern likely does not know about your situation. Stay sharp and fly the standard pattern so your movements are predictable to anyone who can see you.

Should You Troubleshoot Before Declaring Lost Comms?

Yes - spend ten seconds troubleshooting before initiating the lost comms procedure.

Check that you dialed the new frequency correctly, including the decimal. Check your volume control. Verify your headset is fully plugged in. If you have a second COM radio, try it on the last known-good frequency. If you carry a handheld transceiver, grab it.

Ten seconds of disciplined troubleshooting is the difference between a genuine emergency procedure and an embarrassing call to approach control explaining a disconnected headset. It happens. But initiating a lost comms procedure when your radio is actually functional creates a problem where none existed.

How Does ATC Respond When You Go NORDO?

The ATC system is designed with the assumption that radio failures occur. When you go NORDO (no radio), approach control will try you on multiple frequencies and may ask other aircraft to relay messages. Radar facilities watch your transponder target closely. Center controllers coordinate with approach facilities along your route.

Your job is to make their job easier. By squawking 7600, flying your assigned route, maintaining the correct altitude, and beginning your approach at the right time, you give every person in that system the information they need to keep you safe.

How Do You Answer Lost Comms Questions on the Instrument Oral Exam?

The Airman Certification Standards for the instrument rating requires demonstrated knowledge of the lost comms procedure. Examiners ask it often because it tests organized thinking under pressure.

Practice saying this aloud until it comes out smoothly:

“If I lose comms in IMC, I first squawk 7600. For route, I fly the assigned routing, falling back to expected or filed if I don’t have a specific assignment. For altitude, I fly the highest of the minimum IFR altitude for the segment, the altitude I was told to expect, or the altitude I was assigned. For timing, I begin my approach at the EFC time if I was given one, or at my filed estimated time of arrival.”

Say it until the logic is automatic. In the oral exam under pressure, you want it to come out clean - not reconstructed in real time.

Key Takeaways

• Squawk 7600 immediately - it signals your situation to every controller watching your radar return
• Route priority: assigned → vectored → expected → filed (most specific and recent guidance wins)
• Altitude: fly the highest of the minimum IFR altitude, the assigned altitude, and the expected altitude
• Timing: begin the approach at the EFC time if given one, or at your filed ETA - whichever comes first
• Write down EFC times every time a controller gives you one - that habit is cheap insurance
• Spend ten seconds troubleshooting before assuming you have a genuine lost comms situation

FAR 91.185 and additional guidance are available in the FAA Instrument Flying Handbook, downloadable free at faa.gov.