What is the AVEF rule for lost communications during an IFR arrival?

The AVEF rule is a memory aid for the lost communications altitude and route requirements found in 14 CFR 91.185. When radio contact is lost in IFR conditions, a pilot must fly the highest of the Assigned altitude, the Vectored altitude, the Expected altitude (as advised by ATC), or the Filed altitude in the flight plan. Following this rule ensures the aircraft remains at a safe, predictable altitude that ATC and other traffic can anticipate.

How do you complete an approach after losing radio contact on an IFR flight?

Under 14 CFR 91.185, after a lost communications situation, you should proceed to the fix from which an approach begins and commence the approach as close as possible to your EFC time, or if none was received, as close as possible to your filed or amended ETA. You should fly the most recently assigned route, or if being vectored, the direct route to the fix, using the highest altitude from the AVEF rule. Once established at the final approach fix, execute the approach and land as soon as practical to clear the airspace for other IFR traffic.

What's the difference between the Assigned and Expected altitudes in the AVEF rule?

The Assigned altitude is the specific altitude ATC has cleared you to maintain during your current clearance, while the Expected altitude is one that ATC has told you to anticipate for a later portion of the flight, such as a crossing restriction or approach segment altitude. If no altitude has been assigned or expected, you default to the altitude you Filed in your IFR flight plan. The AVEF rule requires you to fly the highest of all four options, providing a built-in safety margin to ensure terrain and obstruction clearance during the lost communications event.

Lost Communications Procedures During an IFR Arrival

Losing two-way radio communications in instrument meteorological conditions (IMC) is one of the most sobering emergencies an IFR pilot can face. Without the ability to talk to ATC, you must become your own controller — anticipating what ATC would have done and flying a safe, predictable path that keeps you separated from other traffic while you complete the approach and land. The FAA has codified exactly how to do this in 14 CFR 91.185, and understanding the rule deeply — not just memorizing an acronym — is the difference between a safe outcome and a catastrophic one.

The core of lost-comm procedure during an IFR arrival is often remembered with the acronym AVEF, which guides you in choosing the correct altitude and the correct route. Let's break down the full regulation and then apply it practically.

The Legal Foundation: 14 CFR 91.185

Under 14 CFR 91.185, the lost communications rules split into two questions: what route do I fly? and what altitude do I fly? The regulation then adds a critical third element: when do I begin the approach? Each of these must be answered correctly to fly a safe, compliant arrival.

The rule applies when you lose two-way radio communication. Importantly, if you can still receive (hear ATC) but not transmit, you are not truly in a lost-comm situation — you may receive light gun signals or ATC may broadcast instructions on your last known frequency. However, if both directions of communication are lost, 91.185 governs.

Route: What Path Do You Fly?

The regulation states that you fly the route you were assigned in your last ATC clearance. If you were being radar vectored when communications were lost, fly a direct course to the fix, route, or airway specified in your last clearance, or — if no such instruction was given — to the route filed in your flight plan. The practical sequence is:

Last assigned route: If ATC told you "fly heading 270, join V25," fly that heading until you can reasonably intercept V25, then join it.
If being vectored with no specific fix mentioned: Fly directly to the fix, route, or airway that was your clearance limit or the next segment of your filed flight plan.
Filed route: If nothing more specific applies, revert to what you filed. Your flight plan is your backup plan.

The intent is predictability. ATC knows your filed route. When you disappear from communications, they will expect you to revert to a logical, filed path. Deviating wildly makes it impossible for them to protect your airspace.

Altitude: The AVEF Rule

This is where the famous AVEF acronym lives. For each segment of your flight, you fly the highest of the following four altitudes:

A — Assigned: The last altitude ATC explicitly assigned you in a clearance. "Maintain 8,000" means 8,000 is your assigned altitude.
V — Vectored (MEA): If you are being radar vectored, ATC is responsible for terrain and obstruction clearance. Once you lose comm and must navigate on your own, you must ensure you are at or above the Minimum En Route Altitude (MEA) for any airway or route segment you are flying. Think of "V" as the altitude needed for the route you're now self-navigating.
E — Expected: Any altitude ATC advised you to expect in the future — for example, "Expect 6,000 in 10 minutes" or an Expected Further Clearance (EFC) altitude. This protects you because ATC issues expect altitudes precisely so you have a reference if communication fails.
F — Filed: The altitude you filed in your flight plan for that segment of the flight.

You fly the highest of whichever of these applies. If your assigned altitude is 7,000, the MEA is 6,000, your expect altitude was 5,000, and you filed 8,000 — you fly 8,000 because that is the highest. This conservative approach maximizes terrain clearance and separation from other IFR traffic.

Why the highest? Because ATC assigns altitudes for separation and terrain clearance purposes. If you're unsure which constraint applies, the highest option keeps you safest and most visible/predictable to controllers working surrounding traffic.

When to Begin the Approach: The Three-Pronged Test

Knowing your route and altitude gets you to the destination, but you also need to know when to start the approach. The regulation establishes a specific sequence, and per 14 CFR 91.185(c)(3) you commence descent or descent and approach as close as possible to:

Your Expected Further Clearance (EFC) time: If ATC issued you an EFC or an expect-approach time, hold until that time and then begin the approach as close as possible to that time.
Your filed Estimated Time of Arrival (ETA): If no EFC was given, plan to arrive over the destination fix at your filed or amended ETA and begin the approach as close as possible to that time.
As close as possible to that time after reaching the destination: If neither of the above applies, proceed to the destination, enter the holding pattern if one is published, and begin the approach as close as possible to your ETA after arriving — not simply the instant you arrive.

The practical effect is this: do not rush to start the approach early. ATC may be sequencing traffic around your estimated arrival. If you arrive before your EFC or ETA and immediately dive for the runway, you may conflict with other aircraft ATC has cleared expecting you to be holding. Patience and predictability are the two cardinal virtues of lost-comm arrivals.

Squawk 7600

One action you must take immediately upon recognizing lost communications is to set your transponder to squawk 7600. This is the universal lost-communications code. It alerts ATC on radar that you have lost comm and allows them to begin protective separation for you. This does not replace the flying procedures — it supplements them. Even squawking 7600, you still fly AVEF routes and altitudes.

VMC Considerations

14 CFR 91.185(b) contains an important conditional: if the failure occurs in Visual Meteorological Conditions (VMC), or if VMC is encountered after the failure, you must continue the flight under VFR and land as soon as practicable. In other words, do not cling to IFR procedures simply because you filed IFR. If you break into VMC, see-and-avoid becomes possible, and the expectation is that you will land at a suitable airport under visual rules. Only if you remain in IMC do the full IFR lost-comm procedures of 91.185(c) fully apply.

Key Numbers and Rules

Squawk 7600 immediately upon recognizing lost comms.
Fly the highest of Assigned, Vectored (MEA), Expected, or Filed altitude — that is AVEF.
Begin approach as close as possible to the EFC time, filed ETA, or (if neither applies) as close as possible to your ETA after arrival.
If in VMC: continue VFR and land as soon as practicable (91.185(b)).
If being vectored when comm is lost: fly toward the next fix, airway, or route in your clearance or filed plan — do not just continue the vector indefinitely.
The governing regulation is 14 CFR 91.185.

Memory Aid

The AVEF mnemonic covers the altitude decision:

A — Assigned: What ATC last told you to maintain.
V — Vectored / MEA: The minimum safe altitude for the route segment you now self-navigate.
E — Expected: Any altitude ATC told you to expect.
F — Filed: Your flight plan altitude for that segment.

Fly the highest of these. A helpful reminder phrase: "Always Very Expertly Fly the highest" — the first word of each sets up the acronym and reminds you of the directive to fly the maximum altitude among all four options.

Common Test Traps

Confusing "highest" with "lowest": Students sometimes think the lowest safe altitude is the answer. The regulation says fly the highest of the four AVEF altitudes — conservative separation, not minimum altitudes.
Forgetting the "V" stands for MEA, not the vectored heading: The "V" reminds you to check the MEA when you were vectored, not to continue the magnetic heading indefinitely.
Starting the approach too early: The rule says to commence the approach as close as possible to EFC or ETA, or after that time upon arrival at the destination — but this means don't start before those markers either. Many students read this as "start the moment you arrive," ignoring a pending EFC time.
Ignoring VMC conditions: If you pop out of the clouds after losing comm, you must go VFR and land as soon as practicable — not continue IFR procedures. The test frequently asks what you do if VMC is encountered after losing radio contact.
Not squawking 7600: Omitting this step is both an operational and knowledge-test mistake. Set 7600 immediately; it is your primary signal to ATC that the failure has occurred.

Lost Communications Procedures During an IFR Arrival (AVEF Rule)