Radio Failure in Controlled Airspace Under VFR
You are flying VFR in Class D airspace in a single-engine aircraft with a Mode C transponder. While receiving a traffic service, your radio fails completely: you can hear nothing and transmit nothing. You are 12 nm from the control zone boundary, tracking towards the aerodrome at 2,500 ft, in good VMC with 15 km visibility and cloud well above you. You have a handheld radio in your flight bag but it is not yet connected. Your transponder is still operating and squawking the code ATC assigned. The aerodrome has a single runway with a light signal lamp.
1. Set out your actions in order, from the moment you recognise the failure.
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1. Fly the aircraft and maintain VMC. Nothing about a radio failure changes the need to aviate. Maintain altitude and heading, and stay clear of cloud.
2. Squawk 7600. Select the radio-failure code on the transponder. This is the primary means by which ATC will identify your situation, and it is more reliable than any attempt to communicate.
3. Try the handheld. Connect and test the handheld radio. If it works, re-establish contact with ATC, state your position, level and intentions, and continue under their instructions. If it does not work, continue with the procedural actions below.
4. Remain outside or leave controlled airspace. Under VFR in Class D, the safest course if you cannot communicate is to remain clear of the control zone and either hold outside the boundary or route to a nearby aerodrome where you can land and telephone ATC. Do not enter the zone without a clearance.
5. If you must land at the aerodrome, join in accordance with the published radio-failure procedure, watch for light signals from the tower, and do not land until you receive a green light. A steady red means give way and continue circling.
2. Explain how the light signals and your transponder interact with ATC's handling of your flight.
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Transponder. Squawking 7600 tells ATC immediately that you have a radio failure. With Mode C they also see your level, which helps them keep other traffic clear of you. ATC will typically treat you as a known radio-failure aircraft and will separate other traffic from you rather than expect you to respond.
Light signals. The light signal lamp is the fallback for exactly this situation. From the tower, a steady green means you are cleared to land; a steady red means give way to other traffic and continue circling; a flashing red means do not land, aerodrome unsafe; a flashing green means return for landing (to be followed by a steady green on final). You must be looking at the tower at the right moment, so fly a predictable pattern and watch the tower continuously on base and final.
Judgement. The interaction matters because ATC cannot ask you what you intend. Your job is to make your intentions obvious: fly a standard pattern, squawk 7600, and only land on a green. If you never see a light, do not land; go around and either try again or divert. The handheld radio, if it works, is far better than light signals and should be tried before relying on the lamp.