Radio failure, intercept and a prohibited area
You are the commander of a business jet on an IFR flight at FL280 through controlled airspace near a coastal prohibited area. Ten minutes after the last position report your radio fails: the headsets go dead on both control units and no amount of switching restores contact. You squawk 7600 and continue on the last cleared route and level while the first officer tries the emergency frequency on a hand-held set. In visual meteorological conditions two fighter aircraft appear, one taking station off your left wing. The leader rocks his wings from level flight, then, after a pause, makes a gentle turn to the right and descends. Your destination is 25 minutes ahead, outside the prohibited area, with fine weather and three hours of fuel. The intercepting aircraft is clearly indicating that you should follow. Your company's AIP extracts show a radio-failure procedure for the destination and nothing about intercepts.
1. What do the wing-rocking and the descending turn mean, and what actions should you take in the cockpit?
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The manoeuvre is the ICAO standard intercept signal. Annex 2, Appendix 1 sets out the signal series the intercepting aircraft uses when radio contact cannot be established. Rocking the wings from level flight means 'You have been intercepted, follow me.' The interceptee acknowledges by rocking its wings and then follows. The turn and descent are the leader positioning the formation; you should follow those manoeuvres, keeping a safe distance, without sudden changes of speed, level or heading, and without attempting to break away.
Practical actions in order: keep squawking 7600; try to establish contact with the intercepting aircraft on 121.5 MHz, on the guard frequency and on the last ATC frequency, saying who you are and that you have received the intercept; switch on landing lights or strobes to help visual identification; note times, headings and levels and keep a log.
If the intercepting aircraft lowers its landing gear, that is the signal for you to land at the aerodrome of its choice; lower your own gear when in a position to land and comply. If the leader breaks away abruptly from the formation, that means you may proceed - but only after he has done so; do not anticipate it. If he flies slowly and you cannot maintain formation, say so on 121.5 or use the standard signals; the intercept is meant to be resolved without manoeuvring the interceptee cannot follow.
2. Your AIP radio-failure procedure says to continue to destination. The intercept is taking you to a military aerodrome 15 minutes away. Which prevails?
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The intercept prevails, and it is not a close call. The radio-failure procedure exists to keep an uncommunicative aircraft predictable inside the ATS system. The moment you are intercepted you are no longer unobserved, and the intercepting aircraft has become the communication channel. Annex 2 gives the pilot-in-command final authority over the aircraft and permits departure from the rules of the air where absolutely necessary in the interests of safety; more importantly, the intercept signals are themselves the instruction you have been given, and following them is how the situation is resolved without escalation.
Ignoring the intercept and continuing to destination would look to the intercepting State like an aircraft disregarding an air-defence instruction near a prohibited area. That can trigger further escalation and, at best, a serious incident report. An aircraft with a failed radio close to restricted airspace is precisely the case the intercept procedure is designed for.
Qualifications that matter in practice: keep trying to reach someone on 121.5, transmit your intentions blind, and tell the intercepting aircraft you have passengers and three hours of fuel if you can. Consider whether the military aerodrome is actually usable - short runway, no approach aids, no handling for a passenger jet. If the diversion creates a genuine fuel or landing-performance problem, say so on 121.5 and follow the leader's subsequent instructions rather than simply ignoring him. After landing, the priority shifts to ATC, the operator and the passengers.
3. What must you do after landing at the military aerodrome, and who must be told?
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On the ground you are an aircraft with a failed radio that has been intercepted. First the practical actions: obtain taxi and parking instructions from the military controller, shut down, keep passengers on board until the local authority and the operator's station arrangements are agreed, and do not let passengers wander around a military base. The commander then contacts ATS and the operator's operations control, explains the radio failure and the intercept, and arranges for handling at the destination to be moved or the flight to be reassigned.
Reporting is not optional. The operator's occurrence reporting system and the national rules on reporting air navigation occurrences both cover a radio failure in controlled airspace. The commander should make a technical log entry, write a report while times and frequencies are fresh, and inform the authority through the operator. The technical investigation starts immediately: both control units, headsets, the audio panel and the hand-held set should be preserved before anyone starts swapping boxes. The aircraft does not depart until the cause is identified and rectified and a fresh ATC clearance is obtained.
Passengers are entitled to an explanation and to be rebooked, and the operator's disruption procedures may need to be opened. There is also a security dimension: a passenger jet has arrived unannounced at a military aerodrome, and the local authority will want the manifest. Finally, the crew should be allowed to rest before returning to duty; the intercept and diversion are themselves fatiguing, and reporting and recovery are part of the same duty.