Radio Failure in Controlled Airspace
You are flying IFR in controlled airspace at FL180 in a pressurised twin. While being vectored for an ILS, your radios fail completely: you can hear nothing and transmit nothing. You are 25 NM from the destination, which has a published ILS and a surveillance radar service. The last clearance was "turn left heading 040, maintain 4,000 ft until established, cleared ILS Runway 22." The weather at destination is 400 ft ceiling, 2 km visibility. Your transponder is serviceable. You have 45 minutes of fuel above final reserve.
1. What is the correct radio-failure procedure and what should you squawk and fly?
Read the worked answer
Standard practice (to be confirmed against the applicable state's AIP and rules):
- Squawk 7600 to alert ATC.
- Continue on the last acknowledged clearance and, if in IMC, follow the published radio-failure procedure for the route or the expected approach. Where no specific procedure is published, the common convention is to maintain the last assigned level for a period, then follow the flight plan route and descend in accordance with the published procedure.
- Fly the last clearance: heading 040 to intercept, then the ILS Runway 22. Because you are already cleared for the approach, continuing it is consistent with the clearance.
- Listen on the appropriate frequency (and use any secondary radio or emergency frequency) in case communications are restored.
- Watch for light signals from the tower if in visual contact.
The reasoning is that ATC expects the aircraft to follow the last clearance and the published procedure, which allows them to protect the airspace. Squawking 7600 and flying a predictable profile is safer than improvising.
2. How does the low ceiling and visibility affect your decision, and what would you do if the approach is not possible?
Read the worked answer
With a 400 ft ceiling and 2 km visibility, the ILS minima must be checked: if the decision height and visibility are at or above minima, the approach can be flown. If the reported weather is below minima, the approach should not be commenced, and a diversion to an alternate with better weather is required.
Decision process:
- Check minima for the ILS and for any alternate.
- If the approach can be flown, continue on the radio-failure profile, squawk 7600, and be prepared for a missed approach; the missed-approach procedure must be flown as published, and ATC will protect the airspace based on the expected profile.
- If not, divert to the alternate, squawk 7600, and follow the published radio-failure procedure for the diversion; if no procedure exists, maintain the last assigned level until clear of controlled airspace, then descend.
- Fuel: 45 minutes above final reserve limits the number of attempts; plan for one approach and a diversion, not multiple attempts.
The exam tests that radio failure does not suspend the need for meteorological minima and fuel discipline; the emergency procedure is a framework, not a licence to press on.