ACS Task IR.VII.A — Loss of Communications (IFR Lost-Comm Procedures)

What does ACS Task IR.VII.A cover?

IR.VII.A is the only task in Area of Operation VII — Emergency Operations — of the FAA Instrument Rating ACS (FAA-S-ACS-8C). Its sole subject is two-way radio communications failure. DPEs consistently report this as one of the most frequently missed knowledge areas on the instrument oral, because the rules contain three independent decision trees — route, altitude, and timing — and applicants routinely mix them up or apply them out of order.

The underlying regulation is 14 CFR 91.185. Two companion regulations round out the task: 14 CFR 91.187, which governs equipment malfunction reports, and AIM 6-4-1, which provides operational guidance on squawk codes, transmitting in the blind, and light gun signals. You must know all three to pass IR.VII.A.

What does 14 CFR 91.185(b) require when communications fail in VMC?

Under 14 CFR 91.185(b), if the failure occurs in VFR conditions — or if VFR conditions develop after the failure — you must continue the flight under VFR and land as soon as practicable. This rule takes priority. You do not execute the IMC procedure of 91.185(c) while you are able to remain in VMC. The DPE may ask whether you'd climb to find VMC versus continuing IFR; the correct answer is that if you can operate VFR, you must.

What route do you fly after losing comm in IMC? (AVE-F)

Under 14 CFR 91.185(c)(1), you fly by the first applicable option in this priority order:

The mnemonic is AVE-F. "Assigned" covers the most common scenario — you have a clearance with a specific route, you fly it. "Vectored" kicks in only when you are actively being radar vectored at the moment of failure, because you have no assigned route segment — you fly direct to the fix or airway the controller was vectoring you toward. "Expected" applies when ATC said something like "expect direct BARKS after DEPOT" — that statement becomes your route. "Filed" is the fallback when ATC gave you no other information.

The most common DPE trap: confusing "vectored" with "last assigned." If you were cleared direct KBOS and were then given vectors, the vectored route takes priority over the original direct clearance for the portion you are currently flying.

What altitude do you fly after losing comm in IMC?

Under 14 CFR 91.185(c)(2), you fly the highest of the following three altitudes for the route segment being flown:

You take the highest — not the last assigned, not the minimum. If ATC assigned 7,000 feet, the MEA is 8,000 feet, and ATC said you could expect 9,000 feet, you fly 9,000 feet. This is the second most common DPE trap in IR.VII.A: applicants default to "last assigned altitude" and miss the comparison step entirely.

The reason for taking the highest is terrain and traffic separation. ATC designs IFR altitude assignments to provide at least 1,000 feet of obstacle clearance (2,000 feet in designated mountainous areas) on the MEA. If the MEA is higher than your last assignment, your last assignment may not clear terrain — you must climb to the MEA.

When do you leave the clearance limit?

Under 14 CFR 91.185(c)(3), the timing rule for leaving a clearance limit depends on what ATC told you before the failure:

The EFC time is critical. When you receive a clearance limit with an EFC — "cleared to KBOS, expect further clearance at 1435" — that 1435 is your trigger. You hold until 1435, then descend and begin the approach. If no EFC was given, you use your own ETA calculated from the filed flight plan. The reason ATC issues EFC times is precisely to give you this timing reference in case of lost comm.

What do you squawk and what else should you do?

Per AIM 6-4-1, after a communications failure you should:

1. 1
   Squawk 7600 (lost communications) on your transponder.
2. 2
   Attempt to reestablish contact on the last assigned frequency.
3. 3
   Try the destination airport ATIS frequency — ATC monitors these and may broadcast instructions.
4. 4
   Try 121.5 MHz (guard) if other attempts fail.
5. 5
   Monitor all appropriate frequencies for light gun signals or ATC broadcasts in the blind.
6. 6
   Transmit in the blind on the last assigned frequency, stating your intentions, position, and altitude, in case your transmitter is working but your receiver has failed.
7. 7
   Execute the 14 CFR 91.185 procedure simultaneously with your communication attempts.

Transmitting in the blind is a key skill the DPE may probe. Your transmitter may be functional even when your receiver is not — a partial failure. ATC can still hear you and will coordinate your arrival accordingly. Continue transmitting position reports even if you receive no response.

What does 14 CFR 91.187 require?

14 CFR 91.187 is a companion regulation that governs equipment malfunction reports during IFR flight. While 91.185 tells you what to do when comm fails completely, 91.187 applies to partial equipment failures — a malfunctioning nav radio, degraded GPS, or comm failure discovered after landing.

Under 91.187(a), the PIC must report any malfunction of navigational, approach, or communication equipment to ATC as soon as practicable. Under 91.187(b), the report must include:

• Aircraft identification
• Equipment affected
• Degree to which the capability of the PIC to operate under IFR in the ATC system is impaired
• Nature and extent of assistance desired from ATC

The DPE may ask whether 91.187 applies to a total comm failure or only to partial failures. The regulation says "as soon as practical" — which is inherently impossible in a total comm failure. The practical interpretation is that 91.187 governs situations where you can still communicate (e.g., one radio failed of two, or a nav radio failed). After a total comm failure and safe landing, notify ATC promptly by the most expedient means available.

Risk Management in IR.VII.A

The ACS requires you to identify risks associated with communications failure before and during flight. Key risk management elements the DPE evaluates:

Preflight mitigation: Verify all comm and nav equipment is operational before departure. Carry published frequencies for destination and alternates. Note EFC times on your flight plan paperwork. A lost-comm event that occurs at a known clearance limit with a filed EFC is manageable; one that occurs mid-route with no EFC and a poorly remembered flight plan route is not.

Receiver vs. transmitter failures: A partial failure — transmitter only or receiver only — requires different action than a total failure. If you can transmit but not receive, continue transmitting and monitor for light gun signals. If you can receive but not transmit, squawk 7600 and listen for ATC broadcasts and expect they will clear the airspace for your arrival.

Crew resource management: In a two-pilot operation, assign one pilot to fly the 91.185 procedure while the other works through the communication troubleshooting checklist. In a single-pilot IFR operation, prioritize aviate and navigate — do not let troubleshooting distract from flying the correct route and altitude.

Skill Elements in IR.VII.A

The ACS skill element requires you to demonstrate the correct lost-comm procedure in a scenario. The DPE may present this as an oral scenario or observe it during the flight portion. You must be able to:

1. 1
   Recognize the symptoms of two-way radio communications failure (no response on multiple attempts, no ATIS audible).
2. 2
   Squawk 7600 and attempt reestablishment per AIM 6-4-1.
3. 3
   Determine the correct route using the AVE-F priority from 14 CFR 91.185(c)(1).
4. 4
   Determine the correct altitude — highest of assigned, minimum IFR, or expected — from 14 CFR 91.185(c)(2).
5. 5
   Determine the correct departure time from the clearance limit using EFC or ETA from 14 CFR 91.185(c)(3).
6. 6
   Continue to the destination, execute the approach, and land.
7. 7
   Report the equipment malfunction to ATC per 14 CFR 91.187 after landing.

What the DPE Looks For

The DPE evaluates three things in IR.VII.A:

1. Regulatory precision: Can you cite 91.185 by section and describe each decision tree — route, altitude, timing — without prompting? Vague answers like "I'd just fly the filed route and stay at my assigned altitude" fail because they ignore the VMC rule, the altitude comparison, and the clearance-limit timing.

2. Scenario application: When the DPE presents a specific scenario ("You're being vectored for the ILS at 6,000 feet, assigned altitude was 8,000 feet, MEA is 7,000 feet, you had an EFC of 1420 — comm fails now"), you must correctly apply all three rules simultaneously. Applicants who know the rules in isolation but stumble on integrated scenarios fail this element.

3. Situational awareness: The DPE expects you to discuss the VMC exception, squawk 7600, transmitting in the blind, and 91.187 — not just the 91.185(c) route and altitude rules. Lost comm is an emergency requiring a complete response, not a single-rule lookup.

Common Errors in IR.VII.A

• Defaulting to last assigned altitude without comparing it to the MEA and expected altitude — the rule requires the HIGHEST of three options, not simply the last assigned.
• Confusing AVE-F order — stating 'filed route' as first priority when you have an active ATC clearance, or ignoring the 'vectored' option when actively being radar vectored.
• Not knowing the VMC exception — attempting to apply 91.185(c) IMC procedures when VFR conditions are available violates 91.185(b).
• Missing the EFC vs. ETA distinction — when an EFC time was issued, you leave the clearance limit at that time, not at your ETA.
• Forgetting to squawk 7600 and attempt to reestablish communications per AIM 6-4-1 — ATC can still work with you if they know what happened.
• Omitting 91.187 — not knowing the four required elements of the malfunction report (aircraft ID, equipment, impairment degree, assistance desired).
• Forgetting to transmit in the blind — if the receiver failed but the transmitter works, ATC may hear you and coordinate your arrival even without two-way comm.

Practice Questions

Frequently Asked Questions

Sources

• 14 CFR 91.185 — IFR Operations: Two-Way Radio Communications Failure
• 14 CFR 91.187 — Operation Under IFR in Controlled Airspace: Malfunction Reports
• FAA Instrument Rating ACS (FAA-S-ACS-8C)
• AIM Chapter 6, Section 4 — Two-Way Radio Communications Failure

This article was researched from FAA primary sources (14 CFR 91.185, 14 CFR 91.187, AIM 6-4-1, FAA Instrument Rating ACS FAA-S-ACS-8C) and cross-referenced against Cornell LII for current regulatory text by MockDPE. Last updated: May 2026. If you spot an inaccuracy, email corrections@mockdpe.org.