FAR Ninety-One Point One Eighty-Five, the Two-Way Radio Communications Failure Procedure, and the AVE-F Memory Aid That Keeps You Legal When the Frequency Goes Silent

FAR 91.185 establishes the two-way radio communications failure procedure for IFR pilots. When your radio dies in IMC, the regulation gives you a specific framework covering which route to fly, which altitude to maintain, and when to commence your approach. The goal is predictability: if every pilot follows the same procedure, controllers can anticipate your path and protect the airspace around you.

Why Does This Regulation Exist?

A radio failure in IMC turns you into an unknown quantity in a system built entirely on communication. ATC cannot issue amended clearances, traffic alerts, or holding instructions. They have no way to know if you’re continuing on your filed route, diverting, or doing something unexpected.

The regulation solves this by making your behavior predictable. Controllers who know you’re following 14 CFR 91.185 can build a picture of where you’re going and when - and clear the route ahead of you. Every specific step in the regulation flows from that single principle.

What Do You Do If You Lose Comms in VMC?

The VMC scenario is straightforward. Continue VFR and land as soon as practicable. You are not required to maintain your IFR clearance or shoot an instrument approach at your filed destination. You have visual reference - use it.

“As soon as practicable” involves pilot-in-command judgment. If you’re five miles from your destination with 4,000-foot ceilings and 10-mile visibility, pressing on makes sense. If there’s a suitable airport directly below you in good conditions and your destination is two hours away, that’s the more practical choice. Factors include fuel, terrain, field elevation, and weather at the nearest suitable airport.

Squawk 7600 the moment you confirm communications are lost - in VMC or IMC. This is the transponder code for lost communications. When approach control or center sees that code on radar, they begin coordinating immediately to keep other traffic clear of your path.

What Is AVE-F, and How Does It Determine Your Route in IMC?

AVE-F is the memory aid for route selection under FAR 91.185. Work through the four options in order and use the first one that applies.

A - Assigned. Fly the route last assigned in your clearance. If ATC cleared you direct to a fix, fly direct. If they cleared you on victor airways, fly those airways. This applies in most lost comms scenarios because most pilots are already established on their clearance when communications fail.

V - Vectored. If you were on radar vectors when communications failed, proceed direct from the point where comms failed to the fix, route, or airway you were being vectored toward. If the controller was vectoring you to intercept the final approach course, go directly to the initial approach fix and join the approach there.

E - Expected. If ATC issued an expected routing during the flight - for example, “expect direct BUZRD after HEXON” - fly that expected routing if no assigned route or vector situation applies.

F - Filed. If none of the first three options apply, fly what you filed in your flight plan. This is the backstop - always available, lowest priority.

What Altitude Do You Fly After a Radio Failure in IMC?

Fly the highest of these three options:

1. The altitude last assigned in your clearance
2. The minimum IFR altitude for your current route segment (MEA, MOCA, or MVA as applicable)
3. The altitude ATC told you to expect

Consider this example: ATC cleared you to 8,000 feet, the minimum en route altitude on the remaining segment is 6,000 feet, and no specific altitude was expected. Last assigned is 8,000. Minimum is 6,000. Fly 8,000.

Now reverse it: ATC cleared you to descend to 4,000 feet, and the radio failed before you reached it. Last assigned is 4,000. Minimum en route altitude is 6,000. Fly 6,000 - even though you were on a descent to four. The regulation protects you from flying into terrain while executing an instruction the system can no longer support with active coordination.

When Do You Start the Approach After Losing Comms?

This is the step most pilots stumble on, and it’s the most consequential from a safety standpoint. The core principle: begin the approach at a time the system can anticipate.

If you received an Expect Further Clearance (EFC) time: Leave the initial approach fix at that time and begin the approach. If you arrive at the fix before your EFC time, enter the published holding pattern and wait. Do not start early.

If you never received an EFC time: Leave the initial approach fix as close as possible to your estimated time of arrival from your filed flight plan. That ETA is what ATC knows about - it’s what the system will plan around. If you arrive at the fix ahead of your filed ETA, hold until as close to that ETA as possible, then commence.

Simple rule: EFC time overrides ETA when you have one. If you don’t have one, use your ETA.

Two Full Scenarios, Applied

Scenario A. Filed ETA at destination is 1520Z. No EFC time given. Radio fails at 1440Z in IMC.

• Squawk 7600
• Route: on an assigned clearance - fly assigned route (A applies)
• Altitude: last assigned was 8,000, MEA on remaining segment is 6,000 - fly 8,000
• Timing: no EFC, so leave the initial approach fix at 1520Z; hold if early

Scenario B. Same flight, but ATC issued an EFC of 1515Z before the radio failed at 1440Z.

Everything is identical except timing. Hold at the initial approach fix until 1515Z, then commence the approach - regardless of your filed ETA. The EFC time takes priority.

What Is ATC Doing While You Fly Lost Comms?

The moment a controller sees 7600 on radar, coordination begins. They issue traffic alerts on active frequencies, coordinate with adjacent sectors to clear your expected route, and pull up your filed flight plan to project your position and arrival time. At your destination, the tower watches for your arrival and may have emergency response on standby.

The system works for you - but only if your behavior matches what it’s designed to anticipate. AVE-F, the altitude rule, and the timing rules are the mechanism that gives controllers the information they need to protect you.

How Do Checkride Examiners Test FAR 91.185?

The Instrument Rating Airman Certification Standards tasks you to demonstrate understanding of two-way radio communications failure. Examiners put you in scenarios - they don’t want to hear you recite letters, they want to see you reason through a situation.

If the oral question is “what do you do if you lose comms in IMC on vectors to the ILS,” the answer isn’t just “V for vectored.” It’s: “I was on vectors, so I proceed direct from the point where comms failed to the initial approach fix and commence the approach from there.” Walk through the logic. Show that you understand why each step exists, not just what the steps are.

Practice this in a chair before you need it in the cockpit. Put yourself on vectors at 6,000 feet, kill the radio, and walk through AVE-F out loud. Run the altitude calculation. Figure out your timing. Build the procedure into reflex, not recall.

Key Takeaways

• Squawk 7600 immediately when you confirm communications are lost - before anything else, in both VMC and IMC
• In VMC, continue VFR and land as soon as practicable; no requirement to maintain IFR clearance
• In IMC, determine route using AVE-F in order: Assigned → Vectored → Expected → Filed
• Fly the highest of last assigned altitude, minimum IFR altitude for the segment, or expected altitude
• Timing: use your EFC time if you have one; use your filed ETA if you don’t - hold at the fix if you arrive early