Receive-only in the Hong Kong TMA: communications failure to diversion
You are flying a DA40, B-HKE, inbound IFR to Hong Kong International (VHHH) from the southeast, level at 8,000 ft in instrument meteorological conditions within the Hong Kong TMA, in radio contact with Hong Kong Approach. Twenty minutes before your estimated approach time the headset fails: you can still hear ATC clearly through the cabin speaker, but neither the PTT nor the boom or hand microphones will transmit, and there is no handheld radio on board. You have fuel for 1 hour 30 minutes and your filed alternate is Macau. The VHHH weather is wind 090° at 10 kt, 300 ft overcast, visibility 2,000 m in rain. To the west, beyond the TMA, the weather is VMC. Approach is calling you again: B-HKE, Hong Kong Approach, say heading.
1. You can hear ATC but cannot transmit. Set out your immediate actions in the first two minutes, including the transponder.
Read the worked answer
- Recognise it: this is a communications failure with reception only. ATC will notice at once because you cannot read back.
- Squawk 7600 with altitude reporting on, so they can identify you positively without voice. 7600 is the correct code for loss of radio communication.
- Keep listening on the assigned frequency. Reception works, so stay with the controller who is already handling you. If an instruction you hear is unambiguous, comply with it and acknowledge by pressing the ident button.
- Check the simple causes: second radio, audio panel selection, a stuck PTT or a failed headset lead will often restore transmission. This costs seconds and may solve the whole problem.
- Do not change level or route immediately because you cannot talk. You are in IMC, so you cannot simply continue VFR; apply the communications failure procedure first.
- Alternate means: 121.5 emergency frequency, relay through another aircraft, and, once on the ground, a telephone report to ATC.
2. State the procedure you will follow in IMC for level and route, including the seven-minute rule, and explain why it exists.
Read the worked answer
- The procedure: maintain the last assigned speed and level, or the minimum safe altitude if that is higher, for seven minutes; then comply with the filed flight plan. Squawk 7600 throughout.
- Why seven minutes: ATC expects a radio-failure aircraft to keep flying the last clearance for a fixed, known period. That lets them separate other traffic from the airspace you will occupy and predict the moment you turn onto your flight-planned route. Without that predictability the procedure would generate conflicts rather than resolve them.
- Then: follow the filed route, and at destination carry out the letdown or approach appropriate to your flight, landing within the period ATC will protect the airspace for.
- Use what you can hear: any instruction ATC transmits must still be followed, even though you cannot read it back. If you hear nothing, apply the procedure as written.
- Destination weather: 300 ft overcast and 2,000 m is likely below your approach limits, so proceed to the filed alternate, Macau, where VMC is reported - the flight plan and alternate exist precisely for this case.
3. On approach at VHHH, unable to transmit, you see from the tower a steady red light, then flashing red. What do these mean and what do you do? What else would you expect on the ground?
Read the worked answer
- Steady red, aircraft in flight: give way to other aircraft and continue circling. Flashing red: the aerodrome is unsafe - do not land. Both are instructions to break off the approach, so you go around.
- With no radio and low weather at VHHH, obey the signals and plan the diversion to your alternate where VMC is reported. Climb on the published missed approach, keep 7600 selected, and if you can still hear the tower, follow any voice instruction that is consistent with what you see.
- Other signals worth knowing: flashing green = cleared to land; on the ground, steady red = stop, flashing green = cleared to taxi, flashing white = return to the starting point, flashing red = taxi clear of the runway in use.
- After landing: taxi clear of the runway and stop. Report the radio failure and your arrival to ATC by telephone or other means, as the communications failure procedure requires, and write up the defect before the next flight.