FRTOL01What Counts as a Radio Failure
A radio failure is any time you can't hold a two-way conversation with the ground station. It's rarely dramatic: the frequency simply goes quiet, or nobody answers your calls.
There are three versions:
- Total failure. You can't hear anything and nobody hears you. Often electrical, or a headset or jack problem.
- Transmitter failure. You can hear the controller, but they can't hear you. You may hear them calling you repeatedly.
- Receiver failure. Your transmissions may be getting out, but you hear nothing back.
In every case the aircraft still flies perfectly well. Aviate, navigate, then communicate: keep clear of cloud and controlled airspace, then work through the problem.
02Run the Checks First
Most "radio failures" turn out to be the pilot's own set-up. CAP 413 lists the basic checks: the frequency, whether the station is open, radio range, volume, the headset and radio, then another frequency or another aircraft. Your aircraft checklist adds the rest:
- FrequencyIs the right frequency set, on the right box, with no transposed digits? Have you flown out of range of the station, or is it closed?
- Volume and squelchIs the volume turned up? Opening the squelch briefly should give you a hiss, which shows the receiver and headset are alive.
- Audio panelIs the correct radio selected for both transmit and receive?
- Headset and jacksAre both plugs fully in? If you have a spare or passenger headset, try it.
- Press-to-talk switchIs it sticking? A stuck switch blocks the frequency for everyone, and you'll hear nothing.
- Another radio or frequencyTry COM 2 if you have one, the previous frequency that worked, another station on your route, or 121.5 MHz. Another aircraft may be able to relay for you.
- ElectricsCheck the avionics master, the ammeter and the radio's circuit breaker, following your aircraft's checklist.
If none of that brings the radio back, treat it as a genuine failure and move on to the procedure.
03Squawk 7600
7600 is the transponder code for radio communication failure. Setting it is the single most useful thing you can do, because it speaks for you on every radar screen that can see you.
Change the code carefully. If you turn the knobs through 7500 or 7700 on the way, you may briefly send the wrong message, so set the code without dialling through them: from 7000, turn the second digit down through 7 to 6. Many modern transponders don't send a new code until you enter it. Leave the altitude-reporting mode on, so controllers can see your level.
Any radar controller who sees 7600 knows something is wrong and will keep other traffic away from you.
Squawk 7600 is not an emergency call. If the radio failure is part of a bigger problem, such as an electrical fire, use 7700 and the Mayday or Pan call order if you can still transmit at all.
04Transmitting Blind
If you can't hear anyone, your transmitter might still work. So you tell people what you're doing anyway, without expecting an answer. That's transmitting blind.
Total or Transmitter Failure
CAP 413 says to start the message with the words "transmitting blind", include who it's for, and say the whole message twice on the frequency you were using. Keep it short: who you are, where you are, and what you intend to do. The examples on this page use the callsign G-JJER, the fictional aerodromes Wrayton and Newbridge, and made-up frequencies and codes.
Transmitting blind, Wrayton Radar, Golf Juliett Juliett Echo Romeo, radio failure, eight miles north of Wrayton, altitude two thousand two hundred feet, squawking seven six zero zero, diverting to Newbridge, estimating Newbridge at tree fife.
(The whole message again, word for word.)
Then listen. If you can hear the controller but they can't hear you, they may ask you to reply by squawking ident or changing your squawk code. Do exactly what they ask: it's how they confirm you're receiving them.
Golf Juliett Juliett Echo Romeo, Wrayton Radar, if you read, squawk ident.
(Press the transponder IDENT button.)
Golf Juliett Juliett Echo Romeo, ident observed, Newbridge informed of your diversion.
Receiver Failure
If you suspect only your receiver has failed, CAP 413 adds the reason to the opening words: "transmitting blind due to receiver failure". Send each report twice, at the times or positions you'd normally report. Anyone listening then knows to stop calling you.
Transmitting blind due to receiver failure, Newbridge Information, Golf Juliett Juliett Echo Romeo, fower miles west of Newbridge, altitude two thousand feet, joining overhead for landing.
(The whole message again.)
05In or Near Controlled Airspace
Without a radio you can't get a clearance, so the rule is simple: if you're outside controlled airspace, stay outside it.
For a VFR flight, the UK AIP (ENR 1.1) sets out the basic actions: set 7600, carry on in visual conditions, land at the nearest suitable aerodrome, and report your arrival to the ATC unit as quickly as you can. Watch for light signals from the ground. If you can't stay in visual conditions, the AIP's IMC procedure applies instead. "Suitable" means somewhere you can land safely, ideally with no controlled airspace in the way.
- Not yet cleared in. Don't enter. Even if you've asked for a crossing, you haven't been cleared until you've heard the word "cleared" and read it back. Route around and divert.
- Already inside on a clearance. The UK AIP and some aerodromes' AD 2 entries publish specific radio failure procedures for their airspace. Follow those. Check the current AIP for the zone you're flying in before you go.
- Under a Basic Service or Traffic Service. Simply divert. A Traffic Service controller will notice you've gone quiet. See Basic Service and Traffic Service for what each covers.
06Arriving at the Aerodrome: Light Signals
At an aerodrome with an ATC tower, the controller can still talk to you with a signal lamp. Join so you can see the tower and the signals square, and watch for the light.
An overhead join is the natural choice: you see the windsock, runway and traffic before you commit. Make your circuit calls blind, and watch the tower on downwind and final.
| Signal | Aircraft in flight | Aircraft on the ground |
|---|---|---|
| Steady green | Cleared to land | Cleared for take-off |
| Flashing green | Return for landing; the landing clearance will follow | Cleared to taxi |
| Steady red | Give way to other aircraft and keep circling | Stop |
| Flashing red | Aerodrome unsafe, don't land | Taxi clear of the landing area in use |
| Flashing white | Land at this aerodrome and go to the apron when cleared | Return to your starting point on the aerodrome |
| Red pyrotechnic | Whatever you were told before, don't land for now | – |
Acknowledge a signal in flight by rocking your wings in daylight (but not on base or final), or at night by flashing your landing light or navigation lights twice. On the ground, move the ailerons or rudder by day, or flash your lights at night. Without ATC there may be no lamp at all, so look out and land only when the runway is clear.
After You Land
Clear the runway, shut down and phone the ATC unit you were working, or the one that was expecting you. Tell them who you are and where you've landed. Until they hear from you, they may be starting overdue action.
07Common Mistakes
- Giving up too soon. Not checking the frequency, volume and headset before declaring a failure.
- Fault-finding instead of flying. Drifting towards cloud or controlled airspace while heads-down in the radio.
- Forgetting 7600, or passing through 7500 or 7700 while setting it.
- Entering controlled airspace on the strength of a request that was never answered.
- Saying a blind transmission once. CAP 413 says twice, starting with "transmitting blind".
- Mixing up the light signals, especially flashing green (come back and land later) and steady green (cleared to land).
- Not phoning in after landing, so a search starts for an aircraft that's sitting safely on the apron.
08Radio Failure in the FRTOL Practical Test
A radio failure is one of the tasks the examiner can give you in the FRTOL practical test.
The examiner wants to hear the procedure in a sensible order: the checks, the squawk, a correctly worded blind transmission said twice, and a clear intention, such as diverting to a named aerodrome. Say "squawking seven six zero zero" so the examiner knows you've set the code. You may also be asked about light signals in the scenario questions afterwards, so learn the table above by heart.
The wording follows our CAP 413 phraseology guide, and numbers use the aviation phonetic alphabet. Lost but with a working radio? That's a different procedure: see London Information radio calls. Near a military zone without a radio? The MATZ and ATZ guide explains why to stay clear.
09Radio Failure Questions
What does squawk 7600 mean?
7600 is the transponder code for radio communication failure. Setting it alerts every radar controller who can see you that you may not be able to hear or talk to them, so they can keep other traffic clear and expect you to land.
What does transmitting blind mean?
It means sending a message without knowing whether anyone can hear it. You start with the words TRANSMITTING BLIND, say the message twice, and then do what you said you would. Your transmitter may still work even when you can hear nothing, so someone may well receive it.
Should I enter controlled airspace if my radio fails?
Not if you haven't already been cleared in. Stay outside, stay in VMC and divert to a suitable aerodrome. If you're already inside on a clearance, follow the radio failure procedure in the current UK AIP and any procedure published for that airspace or aerodrome.
What does a flashing green light from the tower mean?
To an aircraft in flight, a flashing green means return for landing: you'll get a steady green when you're cleared to land. To an aircraft on the ground, a flashing green means cleared to taxi.
Do I need to tell anyone after landing with a radio failure?
Yes. Report your arrival to the ATC unit you were working, or the one expecting you, by the quickest means available, usually a phone call. Otherwise they may start overdue action and a search.
10Official Sources
This guide is a summary. Always check the current official documents.
This guide and the FRTOL app aren't approved by or affiliated with the UK CAA, and they don't replace your instructor or the official documents. Example calls are illustrative. Checked against CAP 413 (edition 24) in November 2026.