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Radio Failure Transponder Code

AIM ¶ 6-4-2 — Radio Failure Transponder Code

AIM 6-4-2 explains transponder operation during two-way communications failure. Squawk 7600 procedures for pilot students preparing for checkrides.

In Plain English

When you lose two-way radio communication with ATC, AIM 6-4-2 recommends setting your transponder to Mode A/3, Code 7600. This special code alerts ATC controllers that you've experienced a communications failure, allowing them to provide separation services and assistance even though they can't talk to you.

Key points to remember:

  • Squawk 7600 to indicate lost communications
  • Use Mode A/3 (the standard altitude-reporting mode pairing)
  • Be aware that radar coverage is not guaranteed — you may be outside an area where ATC can see your transponder return

Operationally, squawking 7600 is one of the first actions in your lost-comm checklist alongside troubleshooting the radio (checking volume, frequency, headset, audio panel, and circuit breakers). Even if you're not sure ATC can see you, setting the code costs nothing and maximizes your chances of being identified. Remember that AIM guidance is recommended practice, while specific lost-comm flight procedures under IFR are governed by 14 CFR 91.185.

AIM Source Text
FAA AIM ¶ 6-4-2
6-4-2. 6-4-2. Transponder Operation During Two‐way Communications Failure If an aircraft with a coded radar beacon transponder experiences a loss of two‐way radio capability, the pilot should adjust the transponder to reply on Mode A/3, Code 7600. The pilot should understand that the aircraft may not be in an area of radar coverage.
Oral Exam Questions a DPE Might Ask
Q1What transponder code should you set if you experience a two-way radio communications failure?
Per AIM 6-4-2, the pilot should adjust the transponder to reply on Mode A/3, Code 7600.
Q2Does squawking 7600 guarantee that ATC will see your aircraft?
No. Per AIM 6-4-2, the pilot should understand that the aircraft may not be in an area of radar coverage, so the transponder reply may not be received by ATC.
Q3What transponder mode is paired with code 7600 during a communications failure?
Per AIM 6-4-2, the transponder should be set to reply on Mode A/3 with Code 7600.
Related Paragraphs in AIM Chapter 6
6-4-1
Lost Communications Procedures
6-4-3
Reestablishing Radio Contact
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AIM 6-4-2 — Transponder Code for Radio Failure