Loss of VHF Communications in IMC
VT-COM is IFR at 9,000 ft in IMC, cleared 'direct XYZ VOR, expect ILS runway 27, squawk 4521.' Ten minutes later both VHF radios fail. The last contact was with Area Control on 128.70. Destination weather is VMC: visibility 8 km, scattered 3,000 ft, wind 270/08. The filed alternate is 25 minutes away with similar weather. The aircraft has 2 hours' fuel, no weather radar, and the pilot is 40 NM from XYZ. The transponder still works. ATC radar coverage exists above 7,000 ft but not below. The pilot has not received a descend clearance; the aircraft remains at 9,000 ft. The destination has an ILS and a published hold at XYZ; the pilot has current charts but no datalink weather. The pilot must decide what to squawk, whether to descend to 5,000 ft, and how to proceed.
1. What should the pilot do immediately after recognising the communications failure?
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The pilot should first fly the aircraft and preserve the last acknowledged clearance. Set the transponder to 7600 to indicate a radio failure. Continue to monitor the last frequency and 121.5 on the remaining audio path if any receiver still works, even if transmission is impossible. Try a second radio only if doing so does not distract from aircraft control.
The pilot should not change altitude simply because a descent to 5,000 ft was expected. No descent clearance was received. Maintain 9,000 ft for the moment, stay on the cleared route direct XYZ VOR, and assess fuel, weather, and terrain. Because the aircraft is in IMC, the pilot should prepare to follow the published lost-communications procedure rather than improvise a visual descent.
2. Should the pilot descend to 5,000 ft? Explain the factors.
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Not immediately. The last clearance contained no descent instruction, so 9,000 ft remains the last assigned altitude. A descent to 5,000 ft without a clearance could conflict with terrain or other traffic and would be difficult for ATC to predict. The expectation of an ILS does not authorise an early descent.
The pilot should consider descending only when established on a published procedure that specifies the altitude, when receiving a new clearance through an alternative means, or when the aircraft is in VMC and the pilot can maintain visual separation and terrain clearance. Destination weather is VMC, but the aircraft is currently in IMC. The absence of radar coverage below 7,000 ft also means ATC may not be able to provide traffic information. The safer plan is to maintain 9,000 ft until the published arrival or hold at XYZ, then follow the lost-communications procedure.
3. How should the pilot proceed toward destination and what should be avoided?
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The pilot should proceed direct XYZ VOR as last cleared, maintain 9,000 ft, and plan to enter the published hold at XYZ. From there, follow the published lost-communications procedure for the destination and the ILS runway 27. Continue squawking 7600 and monitor 121.5. If the aircraft enters VMC and the pilot can maintain visual flight, the pilot may consider landing at a suitable airport, but should first ensure terrain clearance and traffic separation. The filed alternate is available if fuel or weather becomes a concern.
Avoid descending early, switching off the transponder, or diverting without considering the published procedure. Avoid using the absence of radar coverage as a reason to change route unpredictably. If the pilot can communicate through another aircraft or an approved relay, pass the position, level, and intentions. Otherwise, fly a predictable route so ATC can protect the airspace.