IFR Operations

IFR Operations

FAR 91.167–185 / AIM 5–7 • Lost Comms, Alternates, Fuel, Icing, Approaches, Weather, Malfunctions

Know Your Lost Comm Procedures Cold

AVEF for route, MEA for altitude. These aren't just checkride knowledge — they're survival procedures. Practice until the priority order is automatic, and always copy the EFC time. (14 CFR §91.185)

Key Takeaways

  • Lost-comm route follows AVEF in priority order: Assigned, then Vectored, then Expected, then Filed.
  • Lost-comm altitude is the HIGHEST of the MEA, the Expected, or the last Assigned — recomputed each segment.
  • Squawk 7600; if you're in (or reach) VMC, stay VFR and land as soon as practicable.
  • Begin the approach at your ETA or the EFC time, whichever is later; leave a clearance limit (if not the destination) at the EFC.

Lost Communications: Route (AVEF)

  • A — Assigned: Last route assigned by ATC
  • V — Vectored: If being vectored, fly direct to the fix/route/airway specified in the vector clearance
  • E — Expected: Route ATC told you to expect
  • F — Filed: Route filed in the flight plan
  • Apply in this priority order — use the first one that applies
14 CFR §91.185

Lost Communications: Altitude (MEA)

  • Fly the HIGHEST of:
  • M — Minimum altitude (MEA) for each route segment
  • E — Expected altitude (told to expect by ATC)
  • A — Assigned altitude (last altitude assigned by ATC)
  • Altitude may change as you fly each segment — recalculate for each leg
14 CFR §91.185

Lost Comm Procedures

  • Squawk 7600 immediately
  • If failure occurs in VMC or VMC is encountered: Continue VFR, land as soon as practicable
  • If in IMC: Follow AVEF/MEA rules and continue to destination
  • Begin the approach at the EFC time if you were given one — if you were NOT, begin at your ETA. It is one or the other, not whichever is later
  • Leave the clearance limit (if not a fix from which an approach begins) at the EFC time; if no EFC, leave on arrival over it, then proceed to a fix from which an approach begins
KeyMeansNotes
Route — §91.185(c)(1): use the FIRST that applies
A — AssignedThe route in the last ATC clearance receivedYour default
V — VectoredDirect from the failure point to the fix, route, or airway in the vector clearanceApplies while being radar vectored
E — ExpectedThe route ATC advised you may expect in a further clearanceOnly if no route was assigned
F — FiledThe route you filed in the flight planLast resort
Altitude — §91.185(c)(2): fly the HIGHEST of these, per segment
M — MinimumThe minimum IFR altitude for the segment being flownChanges segment to segment — recompute each leg
E — ExpectedThe altitude ATC advised you may expectCounts even though you were never cleared to it
A — AssignedThe altitude in the last ATC clearance receivedDoes NOT automatically win

Route is a priority list — take the first that applies. Altitude is not: you fly the highest of the three, recomputed every segment.

14 CFR §91.185

Communication Best Practices

  • "ATC clears" vs. "ATC advises" — know the difference for lost comm
  • Always write down clearances, especially EFC times
  • Monitor 121.5 MHz if primary fails — ATC may try to reach you
  • Try all radios, switch to previous frequency, try Flight Service (122.2)
  • Cell phone: Last resort, but can work to contact ATC/FSS in an emergency
AIM 6-4-1
Go Deeper
Question about lost-comm rules, the 1-2-3 alternate test, or partial-panel after a vacuum failure? Ask Kit for a CFI-level explanation.
“Walk me through the lost-communications altitude and route rules under 91.185”

Training aid only — verify all data against your POH and current FAA publications.