11.4 14 CFR 91.185 Lost Communications Procedures
Key Takeaways
- Upon identifying two-way radio failure, the pilot must squawk Mode 3/A transponder code 7600 and troubleshoot avionics before applying 14 CFR § 91.185 procedures.
- If two-way radio failure occurs in Visual Meteorological Conditions (VMC), or if VMC is encountered at any point, the pilot MUST continue the flight under VFR and land as soon as practical.
- In Instrument Meteorological Conditions (IMC), the pilot must navigate the Route determined by the AVE-F hierarchy in strict order of precedence: Assigned, Vectored, Expected, or Filed.
- In IMC, the pilot must fly the Altitude determined by the MEA rule: the HIGHEST of Minimum en route IFR altitude, Expected altitude, or Assigned altitude for the specific route segment being flown.
- When reaching a clearance limit from which an approach begins: if an EFC time was received, commence descent and approach at the EFC time; if no EFC was received, commence descent and approach at the filed Estimated Time of Arrival (ETA).
14 CFR 91.185 Lost Communications Procedures
Quick Answer: Under 14 CFR § 91.185, squawk 7600. If in VMC, continue under VFR and land as soon as practical. If in IMC, fly the Route (AVE-F) in order of precedence: Assigned, Vectored (direct to fix/route if lost during vector), Expected, or Filed. Fly the Altitude (MEA): the HIGHEST of Minimum IFR altitude, Expected altitude, or Assigned altitude for each segment. At a Clearance Limit that is an approach fix, begin approach at the EFC time (or at filed ETA if no EFC given).
A complete loss of two-way radio communications while operating under Instrument Flight Rules in IMC is an emergency situation that demands strict adherence to standardized regulatory procedures. Because Air Traffic Control separates other aircraft based on the assumption that the lost-comm aircraft will follow 14 CFR § 91.185, any improvisation or deviation by the pilot creates immediate collision risks.
Immediate Troubleshooting & Transponder Actions
Before assuming complete receiver and transmitter failure, pilots should execute immediate troubleshooting:
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| LOST COMMS TROUBLESHOOTING CHECKLIST |
| |
| 1. Verify Frequency & Audio Panel Configuration: |
| • Check selected frequency against en route chart / approach plate |
| • Verify COM 1 / COM 2 mic selector switches and speaker/headset |
| • Check volume knobs and pull squelch test |
| • Verify headset jacks are securely plugged in |
| |
| 2. Re-establish Contact: |
| • Switch to previous ATC frequency or Flight Service (FSS) RCO |
| • Monitor guard / emergency frequency 121.500 MHz (or 243.0 UHF) |
| • Listen over operational VOR voice channels (HIWAS/TWEB legacy) |
| |
| 3. Set Transponder to Squawk 7600: |
| • SQUAWK 7600 immediately (alerts ATC radar automated trackers) |
| |
| 4. Transmit Blind: |
| • Transmit intentions in the blind: "Transmitting in the blind..." |
| • (Transmitter may still function even if receiver is dead) |
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The Primary Decision Fork: VMC vs. IMC (14 CFR § 91.185(b))
The very first decision in a lost communications scenario depends entirely on the prevailing flight conditions:
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| VMC vs. IMC DECISION FRAMEWORK |
| |
| VISUAL METEOROLOGICAL CONDITIONS (VMC): |
| • If the failure occurs in VFR conditions, OR if VFR conditions |
| are encountered at ANY time during the flight: |
| • RULE: The pilot MUST continue the flight under VFR and land as |
| soon as practical. |
| • Do NOT fly into clouds or continue an extensive IFR route if VMC |
| landing is possible at a nearby suitable airport! |
| |
| INSTRUMENT METEOROLOGICAL CONDITIONS (IMC): |
| • If the failure occurs in IMC, or if weather prevents continuing |
| safely under VFR: |
| • RULE: The pilot MUST execute the codified ROUTE and ALTITUDE rules |
| prescribed in 14 CFR § 91.185(c). |
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"Land as Soon as Practical" vs. "Land as Soon as Possible": "Practical" means using sound aeronautical judgment to land at a safe, suitable airport with appropriate runway length, services, and weather, rather than forcing an immediate off-field landing or landing at an unserviceable strip.
Route to Fly in IMC: The AVE-F Hierarchy
Under 14 CFR § 91.185(c)(1), the pilot must navigate along a specific route selected in strict order of precedence (remembered by the acronym AVE-F):
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| AVE-F ROUTE SELECTION PRECEDENCE |
| |
| Order Code Route Element Application & Priority |
| ----- ---- ----------------- ------------------------------------- |
| 1 A ASSIGNED Route assigned in last ATC clearance |
| received. |
| 2 V VECTORED If being radar vectored, proceed |
| DIRECT from point of radio failure to |
| the fix, route, or airway specified in |
| the vector clearance. |
| 3 E EXPECTED Route ATC advised may be expected in a |
| further clearance (EFC route). |
| 4 F FILED Route filed in the original/amended |
| flight plan. |
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Critical Vector Rule (V in AVE-F)
If communications fail while being vectored off-course by ATC (e.g., "Fly heading 090 for radar vectors to V120"), the pilot must not continue flying heading 090 indefinitely. The pilot must turn and fly direct to the fix, route, or airway specified in the vector instruction.
Altitude to Fly in IMC: The Highest of MEA Rule
Under 14 CFR § 91.185(c)(2), for each route segment being flown, the pilot must maintain the HIGHEST of the following three altitudes:
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| HIGHEST OF M-E-A ALTITUDE MATRIX |
| |
| Letter Altitude Element Definition |
| ------ ---------------------- ------------------------------------ |
| M MINIMUM IFR Altitude Minimum En Route IFR Altitude (MEA, |
| MOCA, MRA, MIA) for the segment. |
| E EXPECTED Altitude Altitude ATC advised to expect in a |
| further clearance (at specified time). |
| A ASSIGNED Altitude Last altitude assigned by ATC. |
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Segment-by-Segment Application
The "highest of MEA" calculation must be applied dynamically to each individual route segment as the flight progresses:
Altitude
10,000 ft | +-----------------+ (Assigned: 10,000)
| | MEA: 10,000 ft |
8,000 ft | +----------------------------+ +-------------+
| | Assigned: 8,000 ft | | Assigned: |
6,000 ft | | MEA: 5,000 ft | | 8,000 ft |
| | (Fly 8,000 ft) | | MEA: 4,000ft|
4,000 ft | | | | (Fly 8,000) |
+-+----------------------------+-----------------+-------------+-->
Segment 1: V244 Segment 2: V244 Segment 3: V244
(Over Plains) (Over Ridge) (Over Valley)
- Segment 1: Assigned = 8,000 ft, MEA = 5,000 ft. Fly 8,000 ft (Assigned is highest).
- Segment 2: Assigned = 8,000 ft, MEA = 10,000 ft. Climb to 10,000 ft upon reaching the fix where MEA rises (MEA is highest).
- Segment 3: Assigned = 8,000 ft, MEA = 4,000 ft. Descend back to 8,000 ft (Assigned is highest again).
Leaving the Clearance Limit (14 CFR § 91.185(c)(3))
What happens when an aircraft reaches its clearance limit without communications? Federal regulations divide this into two distinct scenarios depending on whether the clearance limit is an approach fix:
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| LEAVING THE CLEARANCE LIMIT MATRIX |
| |
| Clearance Limit Type EFC Received? Pilot Action |
| ------------------------- -------------- -------------------------- |
| Fix from which an YES Hold until EFC time. Begin |
| approach begins descent and approach as |
| (e.g., IAF or FAF) close as possible to EFC. |
| |
| Fix from which an NO Hold until filed ETA. Begin |
| approach begins descent and approach as |
| (e.g., IAF or FAF) close as possible to ETA. |
| |
| Fix from which an YES Leave fix at EFC time. |
| approach DOES NOT begin Proceed to approach fix, |
| (e.g., En route NAVAID) hold until ETA, then start. |
| |
| Fix from which an NO Upon arrival at fix, proceed|
| approach DOES NOT begin to approach fix, hold until |
| (e.g., En route NAVAID) ETA, then start approach. |
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Scenario A: Clearance Limit IS an Initial Approach Fix (IAF)
(En Route) ----------> [ IAF (Clearance Limit) ]
│
├─► If EFC received ───► Hold until EFC ─► Start Approach
│
└─► If NO EFC received ─► Hold until ETA ─► Start Approach
Scenario B: Clearance Limit IS NOT an Initial Approach Fix
(En Route) ──► [ En Route NAVAID (Limit) ] ──► Proceed to IAF ──► Hold to ETA ──► Start Approach
│
├─► If EFC: Leave NAVAID at EFC time
└─► If NO EFC: Leave NAVAID immediately upon arrival
Determining Estimated Time of Arrival (ETA)
Under 14 CFR § 91.185, the pilot's ETA is calculated from the filed Estimated Time En Route (ETE) amended by the actual departure time (plus any ATC-advised en route delays). If the aircraft arrives at the approach fix prior to this calculated ETA, the pilot must enter holding at the approach fix until reaching the ETA, then commence the descent and approach.
An aircraft in IMC experiences two-way radio failure while cruising at an assigned altitude of 7,000 feet MSL. The flight plan route enters an airway segment with an MEA of 9,000 feet MSL, followed by a segment with an MEA of 5,000 feet MSL. Which altitudes should the pilot fly?
While being radar vectored off an airway for traffic sequencing in IMC, an aircraft suffers a complete two-way communications failure. According to 14 CFR § 91.185, how should the pilot navigate?
An aircraft in IMC experiences lost communications. The clearance limit is an Initial Approach Fix (IAF) and ATC previously issued an Expect Further Clearance (EFC) time of 1530Z. The pilot calculates the filed ETA as 1545Z. When should the pilot commence the instrument approach?