FAR Explainer · 91.185
14 CFR 91.185 — IFR Lost Communications (AVE-F + MEA Mnemonics, Explained)
Lost-comm route, altitude, and leave-clearance-limit timing under 14 CFR 91.185 — the AVE-F (route) and MEA (altitude) mnemonics and exactly when you start descending.
Practice questions on this regulation
Get DPE-style scenario questions that exercise this rule in context.
14 CFR 91.185 — IFR Lost Communications (AVE-F + MEA Mnemonics, Explained)
What does 14 CFR 91.185 require when two-way communications fail?
14 CFR 91.185(a) states that unless otherwise authorized by ATC, each pilot who has a two-way radio communications failure while operating under IFR must comply with the rules of this section. The regulation branches immediately based on weather conditions at the time of failure.
The critical first question is not "what route do I fly?" — it is "what are the weather conditions right now?" That single question determines which part of the regulation applies, and flying the wrong branch is a serious airmanship error. 14 CFR 91.215 also applies: squawk 7600 on the transponder immediately so ATC can identify the lost-comm aircraft and sequence other traffic accordingly.
What do you do when communications fail in VFR conditions?
14 CFR 91.185(b) is direct: if the failure occurs in VFR conditions, or if VFR conditions are encountered after the failure, each pilot shall continue the flight under VFR and land as soon as practicable.
"As soon as practicable" is not the same as "immediately." It means the nearest suitable airport where you can safely land given aircraft performance, terrain, and traffic. You are not required to land in a field — but you cannot continue pressing into IMC hoping the radio comes back. The word "practicable" gives you reasonable operational latitude; it does not give you license to continue an IFR flight you could safely terminate. DPEs routinely ask for the exact statutory language here — "land as soon as practicable" is the answer, not "land immediately" or "land at destination."
What route do you fly in IMC? The AVE-F mnemonic from 91.185(c)(1)
14 CFR 91.185(c)(1) establishes a four-step route priority. Apply the first item that describes your situation — do not combine them.
| Priority | Letter | Rule | When It Applies |
|---|---|---|---|
| 1st | A — Assigned | The route last assigned in an ATC clearance | You received a specific route clearance before the failure |
| 2nd | V — Vectored | Direct to the fix, route, or airway specified in the radar vector | ATC was radar-vectoring you at the moment of failure — fly direct to the fix the vector was taking you to |
| 3rd | E — Expected | The route ATC advised may be expected in a further clearance | ATC told you to expect a specific route but had not yet formally cleared you on it |
| 4th | F — Filed | The route filed in the IFR flight plan | None of the above apply — fall back to the filed route |
The "V" (Vectored) case trips up many applicants. If you were on a radar vector heading 270 toward the final approach fix when comms failed, you do not turn back to the last charted fix on your flight plan. You fly direct to the fix the vector was guiding you toward. This is the regulation's way of keeping the aircraft on a predictable path that ATC can work around.
What altitude do you fly? The MEA mnemonic from 91.185(c)(2)
14 CFR 91.185(c)(2) requires flying at the highest of three altitudes for each route segment. The mnemonic MEA covers all three, though note the letters map to a different order than the acronym:
| Letter | Altitude Source | Definition |
|---|---|---|
| M — Minimum | Minimum IFR altitude | The charted MEA (Minimum En Route Altitude) or MOCA (Minimum Obstruction Clearance Altitude) for the segment — whichever provides the required IFR protection |
| E — Expected | Expected altitude | The altitude ATC advised you to expect in a further clearance |
| A — Assigned | Assigned altitude | The last altitude assigned by ATC in a clearance |
You fly the highest of whichever of these three applies — not the most recently assigned, and not a combination. If ATC assigned 6,000 feet, the MEA for the segment is 8,000 feet, and ATC told you to expect 7,000 feet, you fly 8,000 feet. The minimum IFR altitude wins because it is the one that guarantees terrain and obstruction clearance plus navigation signal coverage regardless of what ATC planned. This logic protects you if the route you are flying (per AVE-F) differs from what ATC had planned for you.
When do you leave a clearance limit and begin the approach? — 91.185(c)(3)
14 CFR 91.185(c)(3) is the most nuanced part of the regulation and the most heavily tested on oral exams. The rule branches on a single fact: is the clearance limit itself an approach fix?
Case 1 — Clearance limit IS an approach fix (e.g., cleared to the IAF):
- 1If an expect-further-clearance (EFC) time was received: commence descent or descent and approach as close as possible to the EFC time.
- 2If no EFC time was received: commence descent or descent and approach as close as possible to the estimated time of arrival (ETA) as calculated from the filed or amended (with ATC) estimated time en route.
Case 2 — Clearance limit is NOT an approach fix (e.g., cleared to a VOR that is not the IAF):
- 1If an EFC time was received: leave the clearance limit at the EFC time, then proceed to an approach fix and commence descent or approach as close as possible to the filed ETA.
- 2If no EFC time was received: leave the clearance limit upon arrival over it, then proceed to an approach fix and commence descent or approach as close as possible to the filed ETA.
The practical effect of Case 2 is that you hold at the non-approach-fix clearance limit only as long as the EFC requires. Without an EFC, you do not hold at all — you arrive, you leave, you proceed directly to the approach. The regulation is designed to get the aircraft on a predictable approach time that ATC can plan around, even with no radio contact.
What about 91.183 and malfunction reports?
14 CFR 91.183 sets the ongoing IFR communications requirements that 91.185 is contingent upon. Under 91.183, the PIC must maintain a continuous watch on the appropriate frequency and report position, unforecast weather, and other safety-relevant information as soon as possible.
Once comms fail and you are operating under 91.185, 14 CFR 91.187 becomes relevant upon landing: the PIC must report the radio malfunction to ATC as soon as possible after landing. 91.187 closes the loop — it ensures ATC receives a report so they can assess any separation gaps created by the lost-comm event.
The AIM expands on these procedures in section 6-4-1, advising pilots to attempt communication on any available frequency (guard 121.5 MHz, the last assigned frequency, FSS, ARINC) and to try re-enabling the radio before assuming comms are permanently lost. The regulatory floor in 91.185 assumes all reasonable attempts to restore communication have failed.
Worked example: lost comms on an IFR arrival
You are flying IFR from KORD to KMKE in a Cessna 172. ATC clears you to the KMKE VOR at 5,000 feet and advises you to expect the ILS RWY 25L approach, with an EFC of 1342Z. You are currently tracking V100 at 5,000 feet. At 1335Z your radio fails and you are in IMC.
- VMC or IMC check: you are in IMC — 91.185(b) does not apply. Proceed under 91.185(c). Squawk 7600.
- Route (AVE-F): Your last assigned route was V100 direct KMKE VOR. Fly V100 direct to the KMKE VOR per 91.185(c)(1) — first priority, Assigned.
- Altitude (MEA): Last assigned altitude is 5,000 feet. The MEA for V100 in this segment is 4,000 feet. ATC told you to expect 4,000 feet for the approach segment. Highest is 5,000 feet — maintain 5,000 until established on the approach procedure.
- Clearance limit: The KMKE VOR is your clearance limit and it is not the IAF for the ILS RWY 25L. ATC gave you an EFC of 1342Z. Leave the KMKE VOR at 1342Z, proceed to the published IAF for the ILS RWY 25L, and commence descent or approach as close as possible to your filed ETA.
- Report: Upon landing, report the radio failure to ATC per 14 CFR 91.187.
Practice Questions
- 1
You lose communications in VFR conditions while operating IFR. What does 14 CFR 91.185(b) require?
Examiner GuidanceContinue the flight under VFR and land as soon as practicable. The IFR lost-comm procedures in 91.185(c) do not apply when VFR conditions exist or are encountered after the failure. - 2
You were on a radar vector heading 090 toward the KEPEC intersection when comms failed. Per 91.185(c)(1), what route do you fly?
Examiner GuidanceFly direct to KEPEC — the fix the radar vector was taking you to. The 'V — Vectored' priority in AVE-F means you proceed direct to the specified fix, not back to the last charted point on the flight plan. - 3
ATC last assigned 8,000 feet. ATC told you to expect 10,000 feet. The MEA for your current segment is 9,000 feet. What altitude do you fly under 91.185(c)(2)?
Examiner Guidance10,000 feet — the highest of the three. The MEA mnemonic (Minimum / Expected / Assigned) requires the highest of the charted minimum IFR altitude (9,000), the expected altitude (10,000), or the last assigned altitude (8,000). 10,000 is highest. - 4
You are cleared to the FEVER VOR. FEVER is not the IAF. ATC gave you an EFC of 1415Z. At 1410Z you arrive over FEVER in IMC with no radio. What do you do per 91.185(c)(3)?
Examiner GuidanceHold at FEVER (the non-approach-fix clearance limit) until 1415Z — the EFC time. At 1415Z, leave FEVER, proceed to the approach fix, and commence descent or approach as close as possible to your filed ETA. - 5
You are cleared to a VOR that is the IAF. No EFC was received. You arrive at the IAF in IMC with no radio. What do you do per 91.185(c)(3)?
Examiner GuidanceCommence descent or descent and approach as close as possible to your ETA calculated from the filed or amended estimated time en route. Because the clearance limit is the approach fix and no EFC was received, you use the filed ETA — you do not wait or hold. - 6
After landing following a lost-comm event, what does 14 CFR 91.187 require?
Examiner GuidanceThe PIC must report the malfunction to ATC as soon as possible after landing. This closes the loop so ATC can account for any separation or sequencing impacts created by the lost-comm event.
Frequently Asked Questions
Q: What is the first thing to do when you lose two-way radio communications in VFR conditions?
Under 14 CFR 91.185(b), if the failure occurs in VFR conditions, or if VFR conditions are encountered after the failure, you must continue the flight under VFR and land as soon as practicable. Do not continue IFR into IMC if you can safely fly and land VFR.
Q: What does AVE-F stand for in 14 CFR 91.185?
AVE-F is a mnemonic for the route priority sequence in 91.185(c)(1): Assigned (last ATC clearance), Vectored (direct to a fix if being radar-vectored at failure), Expected (route ATC advised to expect), Filed (flight plan route). Apply the first option that fits your situation.
Q: What does MEA stand for in the lost-comm altitude rule?
MEA in the 91.185(c)(2) altitude context stands for the three choices: the highest of the Minimum IFR altitude for the route segment (the charted MEA or MOCA), the Expected altitude ATC told you to expect, or the Assigned altitude from your last clearance. Fly the highest of these three.
Q: When do you leave a clearance limit that is an approach fix under 91.185?
Per 14 CFR 91.185(c)(3), when the clearance limit is the approach fix, commence descent or descent and approach as close as possible to the EFC time if one was received, or to your ETA calculated from the filed estimated time en route if no EFC was received.
Q: When do you leave a clearance limit that is NOT an approach fix?
Per 14 CFR 91.185(c)(3), when the clearance limit is not an approach fix, leave at the EFC time if one was received. If no EFC was received, leave upon arrival over the clearance limit, then proceed to an approach fix and commence descent or approach as close as possible to your filed ETA.
Q: What transponder code should you squawk during a lost-comm event?
Squawk 7600 on the transponder. 14 CFR 91.215 requires ATC transponder equipment to be operated as specified, and 7600 is the universal two-way radio failure code. ATC will see the code and initiate lost-comm procedures on their end.
Q: Does 91.185 apply in uncontrolled airspace?
14 CFR 91.185(a) states the rule applies when operating under IFR. Operations in Class G (uncontrolled) airspace under IFR still require compliance with 91.185 if a clearance was issued. However, ATC cannot issue an IFR clearance into Class G, so the practical scenario is almost always controlled airspace.
Q: What is the difference between 91.185 and 91.183?
14 CFR 91.183 defines the ongoing communications duties of an IFR pilot — maintaining watch on the correct frequency and reporting position and safety information. 14 CFR 91.185 defines what to do when that communications link is lost entirely. 91.183 is the baseline; 91.185 is the contingency.
Sources
- 14 CFR 91.185 — IFR Operations: Two-Way Radio Communications Failure (Cornell LII)
- 14 CFR 91.183 — IFR Communications (Cornell LII)
- 14 CFR 91.215 — ATC Transponder and Altitude Reporting Equipment (Cornell LII)
- AIM Chapter 6 Section 4 — Two-Way Radio Communications Failure
- FAA Instrument Flying Handbook FAA-H-8083-15B
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This article was researched from FAA primary sources (14 CFR Part 91 via Cornell LII, AIM Chapter 6, Instrument Flying Handbook FAA-H-8083-15B) and citing current regulatory text — drafted by MockDPE. Last updated: May 2026. If you spot an inaccuracy, email corrections@mockdpe.org.
Frequently Asked Questions
What is the first thing to do when you lose two-way radio communications in VFR conditions?
Under 14 CFR 91.185(b), if the failure occurs in VFR conditions, or if VFR conditions are encountered after the failure, you must continue the flight under VFR and land as soon as practicable. Do not continue IFR into IMC if you can safely fly and land VFR.
What does AVE-F stand for in 14 CFR 91.185?
AVE-F is a mnemonic for the route priority sequence in 91.185(c)(1): Assigned (last ATC clearance), Vectored (direct to a fix if being radar-vectored at failure), Expected (route ATC advised to expect), Filed (flight plan route). Apply the first option that fits your situation.
What does MEA stand for in the lost-comm altitude rule?
MEA in the 91.185(c)(2) altitude context stands for the three choices in priority order: the highest of the Minimum IFR altitude for the route segment (the charted MEA or MOCA), the Expected altitude ATC told you to expect, or the Assigned altitude from your last clearance. Fly the highest of these three.
When do you leave a clearance limit that is an approach fix under 91.185?
Per 14 CFR 91.185(c)(3), when the clearance limit is the approach fix, commence descent or descent and approach as close as possible to the expect-further-clearance (EFC) time if one was received, or to your ETA calculated from the filed estimated time en route if no EFC was received.
When do you leave a clearance limit that is NOT an approach fix?
Per 14 CFR 91.185(c)(3), when the clearance limit is not an approach fix, leave at the EFC time if one was received. If no EFC was received, leave upon arrival over the clearance limit, then proceed to an approach fix and commence descent or approach as close as possible to your filed ETA.
What transponder code should you squawk during a lost-comm event?
Squawk 7600 on the transponder. 14 CFR 91.215 requires ATC transponder equipment to be operated as specified, and 7600 is the universal two-way radio failure code. ATC will see the code and initiate lost-comm procedures on their end.
Does 91.185 apply in uncontrolled airspace?
14 CFR 91.185(a) says the rule applies when operating under IFR. Operations in Class G (uncontrolled) airspace under IFR still require compliance with 91.185 if a clearance was issued. However, ATC cannot issue an IFR clearance into Class G, so the practical scenario is almost always controlled airspace.
What is the difference between 91.185 and 91.183?
14 CFR 91.183 defines the ongoing communications duties of an IFR pilot — maintaining watch on the correct frequency and reporting position and safety information. 14 CFR 91.185 defines what to do when that communications link is lost entirely. 91.183 is the baseline; 91.185 is the contingency.
- 14 CFR 91.185 — IFR Operations: Two-Way Radio Communications Failure (Cornell LII)
- 14 CFR 91.183 — IFR Communications (Cornell LII)
- 14 CFR 91.215 — ATC Transponder and Altitude Reporting Equipment (Cornell LII)
- AIM Chapter 6 Section 4 — Two-Way Radio Communications Failure
- FAA Instrument Flying Handbook FAA-H-8083-15B
AI-generated study aid — not an official source. This article was written entirely by AI working from FAA primary sources (Instrument Rating ACS, 14 CFR Part 91, Aeronautical Information Manual, Instrument Flying Handbook, and relevant Advisory Circulars), with sources cited inline so you can verify each claim. It has not been reviewed by a CFI, DPE, or other certificated aviation professional. AI can hallucinate, misstate section numbers, and subtly paraphrase regulations in ways that change their meaning. Treat this page as a study starting point only — always confirm any regulatory, procedural, or operational fact against the linked FAA primary document before relying on it for a checkride, a written exam, or a flight. Last updated May 17, 2026. Spotted an error? Email corrections@mockdpe.org.