Lost communications

Keep control while testing the communication path

An unexpectedly quiet frequency does not immediately prove that both radios have failed. A wrong frequency, volume or squelch setting, audio-panel selection, headset connection, stuck push-to-talk switch, receiver/transmitter fault, or electrical failure can produce different symptoms. Maintain aircraft control and the applicable clearance while checking the likely path. Do not spend a long heads-down interval turning knobs in IMC.

Check the selected active frequency and audio/transmit controls, listen for a blocked or continuously transmitting channel, and use a second radio or headset if installed and appropriate. Follow the aircraft checklist for equipment or electrical faults. A reception failure and a transmission failure are different: if you can hear ATC, continue listening and use any available authorized method to acknowledge or relay. Do not reset circuit breakers or turn off a needed bus as a generic radio fix.

Try the previously assigned frequency, another appropriate ATC/Flight Service contact, 121.5 MHz or a relay through another aircraft as available. Monitor a navaid voice channel if equipped and useful. Give identification, position, altitude, last frequency and the problem when contact is established; request relay or the controlling facility's further instructions. Coverage and installed equipment limit the options. Set a functioning transponder to 7600 for two-way communication failure under AIM guidance; a code does not repair the radio or guarantee radar coverage.

AIM 6-4-2/6-4-3: transponder and contact restoration · IFH 11-8–11-9: communication/navigation malfunction

VFR conditions change the plan

Under 91.185(b), if the failure occurs in VFR conditions, or those conditions are encountered after the failure, continue under VFR and land as soon as practicable. This takes precedence over treating the filed destination and lost-communication route as a reason to remain in the IFR system unnecessarily.

“As soon as practicable” calls for judgment. It does not mean landing at the closest unsuitable runway, abandoning weather/terrain clearance, or forcing a landing immediately. Select a suitable airport while maintaining the applicable VFR conditions and account for airspace, traffic and the aircraft's needs. A brief view through a hole in the clouds is not necessarily a usable VFR path to a suitable landing. If this provision cannot be complied with, the IFR-condition procedures in 91.185(c) apply.

The AIM explains that the VFR-condition provision also applies when the failure occurs in Class A airspace. The objective is to avoid unnecessarily extended IFR operation after communications fail; do not generalize the emergency context into routine VFR operation in Class A.

14 CFR 91.185(b): VFR conditions · AIM 6-4-1: as soon as practicable and judgment

Select the route from the actual clearance

If VFR-condition compliance is not available, 91.185(c)(1) gives route priorities. Use the route assigned in the last clearance received. If being radar vectored, use the direct route from the failure point to the fix, route or airway specified in the vector clearance. In the absence of an assigned route, use the route ATC said to expect in a further clearance; if neither an assigned nor an expected route applies, use the filed route.

These are fictional fixes used to explain the rule. The assigned/vector/expected/filed reminder does not resolve an incomplete or misunderstood clearance; clarify vector destinations and clearance limits while the radios still work. Navigation capability, terrain and an actual emergency may require judgment beyond the mnemonic.

14 CFR 91.185(c)(1): route priorities

Reassess altitude for each route segment

For the segment being flown, 91.185(c)(2) uses the highest applicable assigned altitude, minimum IFR altitude, or altitude advised to expect. Do not retain one low minimum for the entire route when terrain and segment minima change. Comply with a minimum crossing altitude or other applicable requirement at its required point; climb early enough to meet it.

The current AIM explains the timing of an expected higher altitude: before its specified time or fix, use the highest assigned or minimum IFR altitude. At the specified time/fix, begin the climb to the advised expected altitude if it becomes the controlling value. If the failure occurs after that specified time/fix, the AIM says the expected altitude is no longer applicable; maintain the highest last-assigned or minimum IFR altitude for the segment. Do not blindly substitute every old “expect” altitude. An expected lower altitude does not override a higher assigned/minimum altitude before the applicable clearance-limit descent provision.

Worked fictional example: assigned 6,000 feet, advised to expect 8,000 at BIRCH. Before BIRCH the segment minimum is 5,000, so maintain 6,000. With the failure before BIRCH, climb to 8,000 at BIRCH. A later segment requires 11,000, so meet that higher minimum where necessary. When its minimum later drops to 7,000, 8,000 remains controlling in this example. This illustrates route-segment reasoning, not an authorization for these invented fixes.

14 CFR 91.185(c)(2): altitude · AIM 6-4-1: expected-altitude timing and worked examples

Clearance-limit timing needs two branches

A clearance limit is the point to which ATC has cleared the aircraft; it is not automatically the airport or an initial approach fix. If the limit is a fix from which an approach begins, commence descent or descent and approach as close as possible to the EFC time received. Without an EFC, use the ETA calculated from the filed or ATC-amended estimated time en route.

If the limit is not a fix from which an approach begins, leave it at the received EFC time; without an EFC, leave upon arrival over it. Proceed to a fix from which an approach begins and commence descent or descent and approach as close as possible to the filed/ATC-amended ETA. In this branch, the EFC controls leaving the limit; it does not replace the ETA for beginning the approach at the subsequent fix.

Keep the clearance, EFC and flight-plan time basis available. EFC means expect further clearance, not a clearance to depart the hold during normal radio operation. A changing GPS arrival estimate alone is not the regulation's filed or ATC-amended ETE basis.

14 CFR 91.185(c)(3): leaving clearance limit · AIM 6-4-1: approach timing

Put route, altitude and timing on one page

Fictional IMC example: cleared to ALDER, a limit that is not an approach-start fix. Your vector clearance specifies BIRCH; after that fix, your assigned route continues to ALDER. Assigned altitude is 6,000 feet, the applicable segment minimum is 7,000, and no expected altitude applies. EFC at ALDER is 15:20Z. Filed or ATC-amended ETA for the destination is 15:40Z, and CEDAR is the appropriate fix from which its approach begins. Assume usable navigation, no other restrictions and sufficient fuel for this example.

After appropriate contact-restoration attempts, apply the vector branch to BIRCH and the assigned route to ALDER, while using 7,000 for the stated segment. Leave ALDER at 15:20Z, proceed to CEDAR and commence descent/approach as close as possible to 15:40Z under the applicable timing rule. The actual approach chart controls its altitudes, entry and missed procedure. State which assumptions would change your decision: VFR conditions becoming usable, a different segment minimum, fuel deterioration or an urgent equipment emergency.

Before a real flight, practice explaining the actual clearance and a radio-failure plan with an instructor. In-flight simulation should preserve safety and real ATC communication as appropriate; this lesson does not ask you to switch off a working radio in the IFR system.

AIM 6-4: radio failure procedures · ACS VII.A: lost communications

Use judgment when the rule cannot solve the hazard

A complete electrical failure may remove communication and navigation together. Fuel, fire, terrain, icing or inability to control the aircraft can make a rote wait until ETA unsafe. The AIM recognizes that regulations cannot anticipate every communication-failure situation and directs good judgment; 91.3(b) allows deviation to the extent required by an in-flight emergency requiring immediate action. This is a necessity-based authority, not routine permission to pick a shortcut.

Reduce workload: maintain reliable attitude and navigation references, use checklists, organize the clearance/timing information and seek communication assistance. Use approved automation only if its information and modes remain trustworthy. With another pilot, assign clear tasks; as a single pilot, defer nonessential tasks. Evaluate a suitable landing option promptly rather than letting troubleshooting consume the fuel and attention needed to reach it.

If communication returns, report what happened, your position/altitude and actions, and obtain clear further instructions. After landing, document the malfunction and decisions for maintenance and training review. A communication failure can be an emergency depending on its circumstances; the PIC must assess that urgency.

AIM 6-4-1: judgment and emergency authority · 14 CFR 91.3(b): immediate-action emergency authority

FLIGHT SCENARIO

What would change your plan?