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Instrument rating · ACS IR.VII.A · lesson pack

Loss of Communications

Why this one matters

Lost communications in cloud feels like an emergency, but the rules are designed so that ATC can predict what you will do and keep everyone else away. Knowing the 91.185 sequence cold turns a frightening silence into a planned flight, and recognizing a simple fix (a volume knob, a headset plug) often ends it in seconds.

1 · Know these cold

  • •Squawk 7600 and try to re-establish contact: check the radio and headset, try the last frequency, the next one, Flight Service, 121.5, or a relay.(AIM 6-4-1, Two-way Radio Communications Failure)
  • •If you’re in VFR conditions or get into them, stay VFR and land as soon as practicable.(14 CFR 91.185)
  • •In IFR conditions, route AVEF: the Assigned route; if being radar vectored, direct from the point of radio failure to the fix, route or airway you were vectored toward; in the absence of an assigned route, the route ATC said to Expect; in the absence of that, as Filed.(14 CFR 91.185)
  • •Altitude, for each segment, the highest of: the last assigned; the minimum altitude for IFR on that segment (the MEA, or a MOCA, MCA or 91.177 altitude where those apply); or the altitude ATC said to expect, once you reach the time or fix given for it. An expected lower altitude never authorizes a descent.(14 CFR 91.185)
  • •If the clearance limit is where an approach begins, start the descent and approach as close as possible to the EFC, or with no EFC, to your ETA (departure time plus the filed or amended time en route). Arriving early, hold there until that time.(14 CFR 91.185)
  • •If the clearance limit isn’t where an approach starts, leave it at the EFC (or on arrival if none), go to an approach fix, and start the descent and approach as close as possible to your ETA.(14 CFR 91.185)

2 · The lesson

Recognize and try to fix it
  • Causes: a radio or electrical failure, a stuck mic, the wrong frequency, volume or squelch, a headset problem, or flying out of range.(AIM 6-4-1, Two-way Radio Communications Failure)
  • Aviate first: fly the airplane or engage the autopilot. Then the simple checks: volume, squelch, the audio panel, the headset jack, the other radio and the last frequency. Don't keep resetting a tripped circuit breaker.(AIM 6-4-1, Two-way Radio Communications Failure)
  • Try Flight Service, 121.5, another aircraft to relay, or a phone if you have signal. Listen on a VOR frequency; ATC may transmit there.(AIM 6-4-1, Two-way Radio Communications Failure)
  • Squawk 7600 so ATC knows.(AIM 6-4-1, Two-way Radio Communications Failure)
The 91.185 plan
  • VFR conditions: continue VFR and land as soon as practicable. That doesn’t mean "at once"; it means the first sensible airport.(14 CFR 91.185)
  • Route: the assigned route; if vectored, direct from the point of radio failure to the fix, route or airway you were vectored toward; in the absence of an assigned route, the route ATC said to expect; in the absence of that, the filed route.(14 CFR 91.185)
  • Altitude, for each segment: the highest of the last assigned, the minimum IFR altitude for the segment, or the expected altitude once you reach the time or fix where it applies. Climb to a higher expected altitude only then; it doesn't apply before.(14 CFR 91.185)
  • Approach timing: at an approach fix, begin descent and the approach as close as possible to the EFC, or if none, to the ETA from departure time plus the filed or amended time en route; hold if you get there early. At a clearance limit that isn't an approach fix, leave it at the EFC (or on arrival) and start the approach as close as possible to the ETA.(14 CFR 91.185)
  • Follow 91.185 so ATC can predict you, unless an emergency requires you to deviate (91.3(b)). You decide whether the failure is an emergency, and use good judgment in situations the rule doesn't cover.(AIM 6-4-1, Two-way Radio Communications Failure; 14 CFR 91.3(b))

Want it all on one page, with scenarios? Read the full lesson.

On the flight

ACS standards

  • Recognize a simulated loss of communication, simulate actions to re-establish it, decide whether to continue or divert, and determine when to begin an approach.(Instrument Rating ACS (FAA-S-ACS-8C), IR.VII.A.S1-S4)

What your instructor is watching for

Your instructor watches for quick troubleshooting, 7600, a clear statement of route and altitude for each segment, and the right approach time.

3 · Say it out loud

Answer each one out loud, then check yourself and mark how it went.

  1. Remember Recall it

    “What does AVEF stand for?”

  2. Understand Explain why

    “Why fly the highest of assigned, MEA and expected?”

  3. Apply Use it on a flight

    “Cleared to 6,000, told to expect 8,000 ten minutes after departure, MEA 5,000. You lose comms right after takeoff in IMC. What altitude do you fly?”

4 · Common mistakes

  • Panicking into a diversion.

    ATC can’t predict you.

    Instead: Follow 91.185 unless safety requires otherwise.

  • Using the wrong altitude.

    Terrain or traffic.

    Instead: Highest of assigned, MEA, expected, per segment.

  • Skipping simple checks.

    Most "lost comms" is a switch or a plug.

    Instead: Check volume, audio panel, headset first.

5 · Quick check

Answer, then reveal. Flag anything you want to see again.

  1. 1. Lost-comms squawk?

  2. 2. Lost comms in VFR conditions: what do you do?

  3. 3. Route order?

  4. 4. Altitude?

  5. 5. When do you start the approach without an EFC?

  6. Scenario6. Holding at your clearance limit, the initial approach fix, with an EFC of 1420. Comms are lost. When do you start the approach?

Trained it? Now prove it: practice loss of communications out loud with our examiner.

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Connect it

One situation that runs across this lesson and its neighbors in the same ACS area. Decide first, then check.

Connect it · Emergency Operations

In IMC, cleared direct to a fix and told to expect 6,000 feet in 10 minutes, you lose two-way radio. Then your attitude indicator fails too.

What route and altitude do you fly, and how do you shoot the approach? Decide, then see the worked answer

Squawk 7600 and try to get communications back: the previous frequency, a NAVAID's voice frequency, Flight Service or ARINC to relay, or 121.5. If you reach VFR conditions, continue VFR and land as soon as practicable. If not, follow 91.185. Route, as conditional rules, not a priority list: the route assigned in your last clearance; if you were being radar vectored, direct from the point of the failure to the fix, route or airway in the vector clearance; with no assigned route, the route ATC told you to expect; otherwise the filed route. You were assigned direct to the fix, so fly direct. Altitude, segment by segment: the highest of the altitude last assigned, the minimum altitude for IFR operations on the route segment you're flying, and the altitude ATC told you to expect. 'Expect 6,000 in 10 minutes' is an expected altitude with a time, not an EFC: the 6,000 counts only from that time, and only when it's the highest of the three; an expected altitude never takes you lower. Re-check the highest at each new segment. The approach: if your clearance limit is a fix where an approach begins, start it as close as possible to the EFC, or your ETA if you have no EFC. If it isn't, leave the clearance limit at the EFC (or on arrival, without one), proceed to a fix where an approach begins, and start as close as possible to your ETA. The most straightforward approach means the one at your destination you can fly on the instruments you have left, ideally straight-in, with the least maneuvering. You don't get a free choice of airport or approach unless you declare an emergency and use your 91.3(b) authority. With the attitude indicator out, cover it and fly partial panel: the turn coordinator for bank; the altimeter, airspeed and VSI for pitch; the heading indicator, if it's good, and the compass for direction; known power settings and small corrections.

14 CFR 91.3, 91.185; AIM 6-4-1; IFH (FAA-H-8083-15B), Partial Panel

Brings together: Loss of Communications · Approach with Loss of Primary Flight Instrument Indicators

Teaching this? The instructor lesson plan →

Study aid, not FAA guidance. Sources: 14 CFR; Aeronautical Information Manual (AIM); Instrument Rating ACS (FAA-S-ACS-8C). Checked against current sources 2026-11-13.