9.loss-of-radio-communications. Loss of Radio Communications (IFR)
A complete or partial loss of two-way radio communication during IFR operations is a serious but manageable emergency. The Federal Aviation Regulations and the Aeronautical Information Manual (AIM) prescribe specific procedures so that ATC can predict the pilot's actions and protect airspace along the expected route. The governing rule is 14 CFR 91.185, supplemented by AIM 6-4-1.
Initial Actions
Upon recognizing a communications failure, the pilot should first attempt to restore communication before committing to lost-comm procedures:
- Check volume, squelch, headset, microphone, and audio panel selections.
- Cycle the COM radio and try the alternate COM.
- Verify the correct frequency; try the previous controller's frequency, FSS (122.2 or published RCO), 121.5 MHz emergency, or an ARTCC frequency from the chart.
- Attempt contact through another aircraft as a relay.
- Use the transponder. Squawk 7600 to alert ATC of the radio failure. If a separate emergency develops, squawk 7700.
- Attempt receiver-only communications: ATC may transmit instructions in the blind on the last assigned frequency, on a NAVAID voice channel, or via VOR identifier interruption.
VFR-On-Top or in VMC
Per 91.185(b), if the failure occurs in VFR conditions, or if VFR is encountered after the failure, the pilot shall continue the flight under VFR and land as soon as practicable. "As soon as practicable" does not mean immediately; the pilot should consider fuel, weather, suitable airports, and passenger needs, but should not continue IFR if VFR flight to a landing is feasible.
IFR Conditions — Route, Altitude, and Clearance Limit
If VFR cannot be maintained, the pilot must continue under IFR using the route and altitude specified in 91.185(c). The mnemonics AVE-F (route) and MEA (altitude) help organize the rule.
Route, in order of priority:
- A — By the route Assigned in the last ATC clearance received.
- V — If being radar Vectored, by the direct route from the point of failure to the fix, route, or airway specified in the vector clearance.
- E — In the absence of an assigned route, by the route ATC has advised may be Expected in a further clearance.
- F — In the absence of an assigned or expected route, by the route Filed in the flight plan.
Altitude, fly the highest of the following for each route segment:
- The altitude or flight level Assigned in the last ATC clearance received.
- The Minimum altitude (converted, if appropriate, to minimum flight level as prescribed in 91.121(c)) for IFR operations — i.e., the MEA, MOCA (within 22 NM of a VOR), MCA, or MVA as applicable.
- The altitude or flight level ATC has advised may be Expected in a further clearance.
This is the MEA mnemonic — Minimum, Expected, Assigned — fly the highest at each segment.
Leaving the Clearance Limit
91.185(c)(3) addresses when to begin descent and approach:
- If the clearance limit is a fix from which the approach begins (e.g., an IAF), commence descent or descent and approach as close as possible to the expect-further-clearance (EFC) time. If no EFC has been received, begin descent and approach as close as possible to the estimated time of arrival (ETA) calculated from the filed or amended estimated time en route.
- If the clearance limit is not a fix from which the approach begins, leave the clearance limit at the EFC time, or if none was received, upon arrival over the clearance limit, and proceed to a fix from which the approach begins. Commence descent and approach as close as possible to the ETA.
Example. A pilot is cleared from KMRY to KSFO via V27, cruise 8,000, expect 10,000 ten minutes after departure, EFC at SFO VOR 1845Z, ETA 1850Z. Comm fails at level-off. The pilot squawks 7600, climbs to 10,000 (the expected altitude is higher than assigned along the airway segments where MEA is lower), continues via V27 (Assigned route), and plans to leave SFO VOR for the approach at 1845Z (EFC), aiming to commence the approach near the 1850Z ETA.
Approach and Landing
Fly any published instrument approach procedure at the destination. The pilot is not restricted to the approach ATC may have been planning to issue. Choose the approach best suited to conditions, equipment, and aircraft capability. Once on the approach, descend on profile and land. After landing, contact ATC by phone as soon as practicable to close the flight plan.
Special Considerations
- Partial failures (transmitter only, receiver only) follow the same routing/altitude logic; squawk 7600 to alert ATC.
- In RVSM or oceanic airspace, additional procedures apply via the appropriate AIP or ICAO Doc 4444.
- Maintain situational awareness on guard (121.5) — ATC may issue instructions there.