Stuck Microphone and Relay on the Company Frequency
You are captain of Beechcraft King Air 200 5Y-XYZ on an IFR flight from Wilson Airport (HKNW) to Nanyuki (HKNY) at FL180. At 45 nm east of Nairobi, Nairobi Control clears: '5Y-XYZ, descend to FL120, report leaving FL180.' As you begin descent, the COM1 display flashes 'STUCK MIC' and a continuous carrier blocks the frequency. You cannot transmit or receive. COM2 is serviceable and tuned to the same frequency. The aircraft has a serviceable transponder, mode C, and an ELT. Another company aircraft, 5Y-ABC, is 15 nm ahead on the same frequency and has just checked in with Control. You have 2 hours fuel, VMC above a broken layer, and no emergency. The transponder is set to 4521 and you are in radar and VHF coverage.
1. What immediate actions do you take, and would you squawk 7600 now?
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The first priority is to stop blocking the frequency. A stuck microphone can prevent every aircraft on the channel from hearing ATC, so isolate COM1: deselect it on the audio panel, turn its volume/squelch off, or pull its circuit breaker if that is the approved drill. Do not simply keep transmitting. Then select COM2, confirm the correct frequency, and attempt contact with Nairobi Control. If COM2 works, you have not suffered a communications failure in the regulatory sense and you should not squawk 7600. Continue the last clearance: descend to FL120 and report leaving FL180 when able. Tell ATC what happened: 'Nairobi Control, 5Y-XYZ, COM1 stuck microphone, now on COM2, descending FL120, leaving FL180.' Squawk 7600 only if you cannot establish two-way radio contact on any available means. A relay through 5Y-ABC is preferable to declaring a failure while COM2 is serviceable. Also consider that the transponder code 4521 should remain unless ATC instructs otherwise; do not change to 7600 prematurely.
2. Write the relay request you would make to 5Y-ABC and explain what information must be passed.
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A concise relay request would be: '5Y-ABC, 5Y-XYZ, request relay to Nairobi Control. COM1 stuck microphone, now on COM2. Descending FL120, leaving FL180. Request confirmation of clearance and further instructions.' The relay aircraft must pass three things: who you are, what has failed, and what you need. It should also pass your last clearance and your present level, because ATC needs to know whether you are still following the clearance and whether separation is affected. Avoid a long narrative on the frequency. If ATC asks you to change frequency, the relay aircraft should pass the frequency and you should read it back through the relay. Do not use 121.5 for a routine relay if COM2 is working on the assigned frequency; 121.5 is an emergency frequency and should be kept clear for distress and urgency traffic. After the event, record the failure and any frequency blockage in the technical log.
3. What frequency-management principles apply when using 121.5 and the company frequency in this situation?
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The assigned ATC frequency remains the primary frequency. If COM2 is now your only serviceable radio, it must stay on the ATC frequency so you can receive clearances. 121.5 is primarily for emergency and urgency communications and for direction-finding; it is not a routine company or relay channel. If you have a third radio or a handheld, monitoring 121.5 is good practice, but do not sacrifice the ATC watch to do it. The company frequency may be useful for engineering advice or to ask another company aircraft to relay, but it must not replace ATC communication. If you use the company frequency, keep it brief and return to the ATC frequency. Remember that a stuck microphone on one radio can block the whole channel, so correct isolation of the failed unit is itself a frequency-management action. Finally, if you later have to use 121.5 because all normal frequencies fail, announce your callsign, position and problem clearly, and keep transmissions short.