Radio failure
What an aircraft does when a trainer fails its radio, in what order, and why.
The aircraft loses its radio, stops answering and keeps flying its last clearance. Unless only its transmitter failed, it also stops taking new instructions. The overview explains how any emergency starts, is steered and ends.
What you type
| Command | What fails |
|---|---|
emergency comms | Everything. The crew hears nothing and cannot transmit. |
emergency comms transmitter | The transmitter only. The crew hears you and follows your instructions, but cannot answer. |
emergency comms unaware | The same as the first, but the crew has not noticed. |
Each of them starts at once, after a number of simulated minutes with in, or at a fix with at
(When it starts). The timing goes after the variant, for example
emergency comms transmitter at ROKIL.
What happens, in order
- At the start the aircraft stops answering on the frequency. In the complete failure and the unaware case it also stops taking new instructions. It holds the heading, level and speed it was last cleared to. Instructions it had already read back are still flown.
- 30 seconds to 2 minutes later it sets squawk 7600. The trainer is told beforehand. In the unaware case it never sets a code.
- Until you end it it keeps its last clearance and stays silent. In the complete failure it keeps 7600, because it does not hear a new code. With only the transmitter failed it sets any code the trainee assigns, which is how the trainee can test it.
What the aircraft tells you
With TST01 as the aircraft, the messages in its private window are:
| When | Message |
|---|---|
emergency comms | Radio failure started. TST01 is silent and ignores frequency instructions. TST01 squawks 7600 in 30 to 120 s. |
emergency comms transmitter | Transmitter failure started. TST01 follows frequency instructions and idents, but never transmits. TST01 squawks 7600 in 30 to 120 s. |
emergency comms unaware | Unnoticed radio failure started. TST01 is silent, ignores frequency instructions and keeps its squawk. |
emergency comms in 10 | Radio failure starts in 10 min. |
emergency comms at ROKIL, ROKIL on the route | Radio failure starts at ROKIL. |
emergency comms at ROKIL, ROKIL off the route | ROKIL is not on TST01's route. Radio failure starts when TST01 passes abeam it within 5 NM. |
| 7600 is set | TST01 now squawks 7600. |
emergency status | Radio failure started 40 s ago. TST01 squawks 7600 in 43 s. |
emergency pause, before 7600 | Radio failure on hold. TST01 stays silent and keeps flying. |
emergency cancel | Radio failure ended. TST01 mentions it in its next reply on the frequency. |
What the trainee sees and can test
| Complete | Transmitter only | Unaware | |
|---|---|---|---|
| Answers on the frequency | none | none | none |
| Follows new instructions | no | yes | no |
| Squawk | 7600 after 30 s to 2 min | 7600 after 30 s to 2 min | unchanged |
| "If you read, squawk ident" | no reaction | the aircraft idents | no reaction |
A trainee who finds that the aircraft idents can keep controlling it by asking for an ident or a code change as the acknowledgement of each instruction.
Why
| Behaviour | Basis | Source |
|---|---|---|
| Keeps the last clearance it read back | Rule | SERA.14083 (EU 923/2012 as amended by 2024/404) |
| Sets 7600 | Rule | SERA.14083(c)(2); ICAO Doc 4444 8.8.3.1, which sets it for a transmitter failure too |
| Sets 7600 even if ATC assigned a code earlier | Rule | SERA.14083(c)(2) |
| 7600 comes 30 s to 2 min after the failure | Our decision | No source gives a time. The rules count from the moment the crew notices, and have it try to make contact first. On a busy approach frequency an unanswered call is noticed within seconds. |
| The unaware crew sets no code | Our decision | A crew that has not noticed has no reason to. The ICAO EUR OPS Bulletin 2021_001 describes prolonged losses of contact in which the crews did not know it was lost. |
| Idents when asked, in the transmitter-only case | Rule | SERA.14083(b)(1); ICAO Doc 4444 8.8.3.1 |
| The first answer after the end (below) | Our wording | No source prescribes what a crew says when contact on its own frequency returns. The sentences follow what crews in investigated cases said. |
What it does not do yet
The aircraft keeps its last clearance for as long as the failure runs. In reality, after 20 minutes it would follow the radio failure procedure of SERA.14083 (rejoin its route, fly to the approach fix, hold and land). That procedure is not simulated yet. Do not mark a trainee down for expecting it.
How it ends
emergency cancel restores the radio. If the failure had already started, the next answer to a
trainee on the frequency starts with one sentence, depending on what failed:
| Variant | First answer starts with |
|---|---|
| Complete | "We had a radio failure, reading you now." |
| Transmitter only | "Our transmitter had failed, we heard your calls." |
| Unaware | "Sorry, we missed your calls." |
After that the aircraft answers normally. If it had already set 7600, it keeps it until the trainee assigns a new code. Cancelled before it started, the emergency changes nothing on the frequency.
Sources
- Commission Implementing Regulation (EU) No 923/2012 (SERA), as amended by (EU) 2024/404, with its AMC and GM (EASA Easy Access Rules for SERA, August 2025)
- ICAO Doc 4444, PANS-ATM, 16th edition, consolidated to Amendment 13
- UK CAA CAP 413, Radiotelephony Manual, edition 24, and CAP 493, Manual of Air Traffic Services Part 1, edition 12
- DFS/BAF NfL 2026-1-3969, procedures in the event of radio failure
- FAA Pilot/Controller Glossary and Aeronautical Information Manual, chapter 5 and 6
- ICAO EUR OPS Bulletin 2021_001, loss of communication
- Investigation reports: AAIB AAR 2/2008 (G-EUOB), AAIB Bulletin 10/2011 (N850TV), AAIB-28925 (G-NPTF), BEA interim report of July 2025 (EI-NSF), ATSB AO-2013-066, PKBWL 1249/16, the FAA transcripts of NWA188 (2009)
- IVAO examiner handbook "Emergency during exam and training sessions", version 1.1 (June 2020)