What transponder code do you squawk for lost communications?

Squawk **7600**. It is the internationally recognized discrete code for two-way radio communication failure. ATC facilities that see 7600 on their scope immediately begin coordinating airspace protection along your expected route.

What does AVE F stand for in FAR 91.185?

AVE F is the route priority mnemonic: **Assigned** (last assigned route), **Vectored** (continue toward the fix you were being vectored to), **Expected** (a route ATC told you to expect), and **Filed** (your original flight plan route). You use the first one that applies, in that order.

Why do you fly the highest of the three altitudes during lost comm in IMC?

The highest altitude gives you terrain protection and reflects the route's actual requirements. The MEA guarantees obstacle clearance; the expected altitude typically reflects rising terrain or MEAs ahead; combining them and taking the highest keeps you where the system intends you to be.

What is an EFC time and why does it affect lost comm timing?

An Expect Further Clearance time is a specific time ATC issues when they anticipate a delay in your onward clearance - typically during a hold. If you received an EFC and lose comm, hold at your clearance limit and depart at the EFC time. Without an EFC, use your filed ETA as the timing reference.

What should you check before declaring a genuine lost comm situation?

Verify the failure is real before committing to the procedure. Check your audio panel selector position, check squelch, try a second radio, try a different frequency, and try guard on 121.5 MHz. A misconfigured audio panel is not a failed radio - brief confirmation is worth the few seconds it takes.

Federal Aviation Regulation Ninety-One Point One Eighty-Five, the Lost Communications Procedure, and the Two Mnemonics That Keep You Legal and Safe When the Radio Goes Dead

Federal Aviation Regulation 91.185 covers one of the most consequential scenarios in instrument flying: your two-way radio fails while you’re operating IFR inside the instrument system with an active clearance. Understanding this regulation before the oral exam is necessary. Keeping it sharp after the checkride is what actually matters. Here is how the procedure works, why each element is ordered the way it is, and how to walk through it correctly under pressure.

What Should You Do the Moment You Realize Your Radio Has Failed?

Before working through route or altitude, do one thing immediately: squawk 7600 on your transponder.

7600 is the internationally recognized discrete transponder code for lost communications. The moment it appears on an ATC radar scope, controllers know the nature of the situation. They begin coordinating between facilities, start clearing the airspace along your expected route, notify your destination, and begin looking for you on guard frequency 121.5 MHz. Your transponder becomes your voice when your radio cannot.

Also confirm the failure is real before committing to the procedure. Check your audio panel - an intercom-only selector position is a common culprit. Check squelch. Try a second radio if you have one. Try a different frequency. Try guard. A misconfigured audio panel is not a failed radio, and the cost of a brief confirmation check is far lower than declaring lost comm prematurely.

Does FAR 91.185 Apply If You Can Still Receive ATC Transmissions?

FAR 91.185 specifically covers two-way radio communication failure. If your receiver is still working, you have additional options available.

You can acknowledge clearances by squawking IDENT when ATC asks you to. Near a towered airport, you can watch for and follow light gun signals. These options exist precisely because partial radio failure is a different situation than total failure - and controllers can still work with you if they can reach you one direction.

What Do You Do If You’re in VMC When Communications Fail?

If you are in visual meteorological conditions when the radio fails, the regulation is straightforward: fly VFR and land as soon as practicable.

If you can see and be seen, exit the instrument system. Descend below the cloud layer, clear congested controlled airspace, and land somewhere sensible. Call ATC from the ground.

The word practicable matters here. It is not the same as possible. The regulation does not require you to divert to the nearest patch of pavement regardless of circumstances. It requires reasonable judgment - consider terrain, weather, airport suitability, and proximity to your destination.

What Is the AVE F Mnemonic and How Do You Apply It in IMC?

If you are in instrument meteorological conditions when communications fail, there is no going VFR. You stay in the system and work through three questions: route, altitude, and timing.

For route, use the mnemonic AVE F - in that priority order:

A - Assigned: Fly the route most recently assigned in your last clearance. Direct to a fix, an airway, a published routing - whatever ATC most recently gave you.
V - Vectored: If you were being radar vectored when comm failed, continue toward the fix ATC was vectoring you to, then connect back to your filed or assigned routing.
E - Expected: If ATC told you to expect a specific route further along (“expect direct destination after NEXTT”), fly that expected route. Both you and ATC share that expectation, and the regulation treats it as usable guidance.
F - Filed: If none of the above applies, fly the route in your original flight plan.

The priority runs from most recently communicated to least recently communicated. When you disappear from frequency, ATC works through this same list - coordinating between facilities, protecting airspace along your most likely path. AVE F keeps you where they’re looking.

How Do You Determine Your Altitude During Lost Comm?

Fly the highest of these three altitudes:

The Minimum Enroute Altitude (MEA) for the airway segment you’re currently flying
The altitude ATC told you to expect in a further clearance
The altitude ATC last assigned you

You must compare all three every time. The MEA is the floor - it exists to keep you clear of terrain and obstacles. The expected altitude reflects what the route ahead requires. When ATC assigns a higher expected altitude, it’s typically because MEAs or terrain demand it further along. Flying the highest of the three puts you where the system intends you to be.

Example: You’re cleared to 6,000 feet. The MEA on the airway ahead is 8,000 feet. ATC said expect 10,000 feet in 20 miles. You lose comm. Your assigned is 6,000. Your minimum is 8,000. Your expected is 10,000. Climb to 10,000. That is the call - compare all three, take the highest.

The oral exam mistake to avoid: picking one altitude without comparing the others. “I’d fly my assigned” is an incomplete answer if the MEA or expected altitude is higher.

When Do You Leave the Clearance Limit and Begin Your Approach?

This depends on whether ATC issued you an Expect Further Clearance (EFC) time.

If ATC gave you an EFC time: Fly to the clearance limit. If you arrive before the EFC time, hold. Depart the clearance limit and begin the approach at the EFC time.

If ATC did not give you an EFC time: Depart the clearance limit and begin the approach as close as possible to your estimated time of arrival, calculated from the estimated time en route in your filed flight plan.

That second rule is the one that catches instrument students. The regulation treats your filed ETE as a schedule - not just an approximation. ATC plans around that clock. If your filed ETA is 1445, they’re clearing the approach environment for 1445. If you arrive at 1443, hold briefly. If you arrive at 1447, start immediately - you are already past your ETA.

Your filed estimated time en route matters beyond routine ATC planning. In a lost comm scenario, it becomes the timing reference that you and ATC are both working from.

A Complete Lost Comm Scenario Walked Through

Depart IFR. Destination 90 miles out. Cleared via departure procedure, direct waypoint, Victor 12 to destination. Maintain 6,000, expect 9,000 ten minutes after departure. No EFC time. Departed at 1400. Handed to center. Check in. Silence. Solid IMC.

Step 1 - Squawk 7600.

Step 2 - Assess conditions. IMC. Staying in the system.

Route (AVE F). Most recently assigned: direct waypoint, then Victor 12 to destination. Continue on that routing. (A - Assigned)

Altitude. Assigned: 6,000. MEA on Victor 12: 8,000. Expected: 9,000. Climb to 9,000.

Timing. No EFC time. Filed ETE: 45 minutes. Departed 1400, so ETA is 1445. Fly Victor 12, arrive at destination near 1445, begin approach.

Meanwhile, center has notified approach, approach has notified the tower, traffic has been cleared. They’re watching for a 7600 squawk. When you land and call the ground phone, the system did exactly what it was designed to do.

Key Takeaways

Squawk 7600 immediately - it signals lost comm to every facility that sees your transponder return.
In VMC, fly VFR and land as soon as practicable using reasonable judgment about where.
In IMC, use AVE F (Assigned, Vectored, Expected, Filed) to determine your route - in that priority order.
For altitude, fly the highest of your assigned, expected, or MEA - compare all three, every time.
For timing, depart the clearance limit at your EFC time if one was issued; otherwise fly your filed ETA as a schedule.
The entire procedure keeps you predictable - ATC is working the same list you are.