IFR Lost Comms Procedures – Essential Guidelines

Understanding IFR Lost Comes Procedures

Losing radio contact during an Instrument Flight Rules (IFR) flight is a critical situation, but standardized procedures under Federal Aviation Regulation (FAR) 91.185 exist to maintain safety.

If you suspect a communication failure, start with troubleshooting. Try contacting ATC on the last assigned frequency, then a previous one, or switch to a secondary radio. At the same time, set your transponder to squawk 7600 to immediately alert ATC of your situation.

Should attempts to restore contact fail, FAR 91.185 specifies your flight path and altitude. Your route follows the AEF principle (Assigned, Vectored, Expected, Filed), while your altitude is the highest of three options: Minimum IFR Altitude (MEA), Expected, or Assigned. These rules create a predictable path for ATC. The procedure typically concludes with a timed approach, unless you encounter VFR conditions, in which case you must land as soon as practicable.

The AEF Principle – What It Means

In a lost communications scenario, the AEF principle determines your route. It’s a memory aid for the required sequence—Asigned, Vvectored, Eexpected, and Fled. Following this hierarchy ensures your flight path is predictable, allowing ATC to maintain safe separation with other aircraft.

The logic follows a top-down approach based on the most recent clearance received:

• Assigned: Follow the route last Assigned by ATC in your most recent clearance. For instance, if cleared “direct to the ABC VOR, then via V123,” that’s the path you take.

• Vectored: If you were being radar Vectored when communication was lost, fly directly to the fix, route, or airway specified in the vectoring instruction. You do not continue on the last assigned heading indefinitely.

• Expected: If you haven’t been assigned a route or given a vector, you fly the route ATC advised you to Expect in a future clearance, such as, “expect direct to XYZ after passing the DEF intersection.”

• Filed: Finally, if none of the above apply, you must revert to the route you originally Filed in your flight plan.

This logical progression ensures your actions align with what ATC expects. Together, this route guidance and the corresponding altitude rules create a complete framework for navigating a lost communications scenario.

Altitude Management During Communication Loss

Just like the AEF principle for routing, altitude requirements determine your altitude to ensure obstacle clearance and separation from other IFR traffic. You must adhere to a strict, three-tiered hierarchy.

The rule is simple: fly the highest of the following three altitudes for your current route segment:

• Minimum IFR Altitude: This is the Minimum En route Altitude (MEA) or any other applicable minimum altitude for your specific route segment. It guarantees terrain and obstacle clearance.

• Expected Altitude: Any altitude ATC has advised you to expect in a future clearance (e.g., “climb and maintain 8,000, expect Flight Level 240 in ten minutes.”).

• Assigned Altitude: The last altitude assigned to you by ATC.

Remember this with the mnemonic for this hierarchy is MEA: fly the highest of the Mminimum, Eexpected, or Asigned altitude. This protocol ensures your vertical profile is predictable, enabling ATC to protect the surrounding airspace.

Maintain this altitude until reaching the clearance limit or an initial approach fix. You then commence the descent and approach as close as possible to your Expect Further Clearance (EFC) time or, if none was issued, your filed Estimated Time of Arrival (ETA). This precise timing allows ATC to safely sequence your arrival.

Understanding MEA’s and MSA’s

To apply the altitude rules correctly, you need to understand Minimum En route Altitude (MEA). This is the lowest published altitude between navigation fixes that guarantees:

• Adequate navigation signal reception

• Reliable two-way communication with ATC

• Safe obstacle clearance

Another critical altitude, often found on approach plates, is the Minimum Safe Altitude (MSA). While an MSA provides at least 1,000 feet of obstacle clearance within a specified radius (typically 25 nautical miles), it’s crucial to remember its limitations. Unlike an MEA, an MSA is for emergency use and does not guarantee navigation signal coverage or communication capabilities.

In a lost communications scenario, the MEA acts as the ‘Minimum’ altitude in the selection hierarchy—the safety floor for the en route portion of your flight. It’s what guarantees terrain clearance and helps establish the predictable flight path ATC needs.

Steps to Take After Losing Communication

Troubleshooting Radio Failures

Before assuming a total radio failure, follow a systematic troubleshooting process. The recommended steps include:

• Double-check the last assigned frequency, then try the previous one.

• Attempt to contact a Flight Service Station (FSS).

• Ask another aircraft to relay your call to ATC.

• Use voice-capable VOR’s if available.

• Transmit on the 121.5 MHz emergency (guard) frequency.

After exhausting these options, confirm the failure and ensure your transponder is squawking 7600.

Navigating VFR Conditions After Lost Comes

If you encounter Visual Meteorological Conditions (VMC), the IFR lost communications procedures no longer apply. Your new objective is to continue the flight under VFR and land as soon as practicable.

‘Land as soon as practicable’ means using good judgment, not an immediate emergency landing. Select a suitable airport based on factors such as runway length, available services, and your familiarity with the area. Keep your transponder on 7600 and focus on visual navigation.

When approaching a towered airport, watch the control tower for light gun signals to receive landing clearance. This non-verbal communication is how ATC safely integrates your aircraft into the traffic pattern.