Total VHF failure at FL300 with a CB line ahead and no extra fuel
You are the FE on a Kenyan-registered freighter, night IFR at FL300, 210 nm from Mombasa on the flight-planned route, cleared to descend at pilot's discretion to FL140 by Mombasa approach. The No. 1 VHF fails; 4 minutes later the No. 2 fails after a brief squeal. There is no HF or SATCOM. Transponder and TCAS are serviceable. Weather radar shows a line of embedded cells 30 nm west of Mombasa, tops above FL400, moving east at 15 kt. Mombasa 2050Z: 180/12 kt, visibility 4,000 m in thunderstorm rain, broken 800 ft, few cumulonimbus, QNH 1010, TEMPO 1,500 m. Malindi, 50 nm north-east of Mombasa, is CAVOK. Fuel on board 3,000 kg, cruise burn 1,150 kg/h, hold burn at FL140 1,100 kg/h, final reserve 45 min, no extra fuel carried. Terrain west of Mombasa rises to 4,000 ft.
1. Set out your lost-communication actions and state exactly what route and levels you would fly.
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Actions: squawk 7600 immediately so the transponder does the talking, switch both radios to 121.5 and monitor, try the company frequency and attempt a relay through any aircraft in range - a relay is often faster than the procedure. Turn on all exterior lights, watch TCAS and keep to the last acknowledged clearance while all this happens.
Route and levels: fly the route and altitudes last acknowledged in the clearance, and where that is not specific enough, the flight-planned route at the planned levels, never below the minimum safe altitude for the area. With terrain to 4,000 ft west of Mombasa, that means no descent off the airway track until established on a published segment or above the grid MSA. I would descend at pilot's discretion to FL140 as cleared, since that clearance was acknowledged, but I would hold FL140 rather than continue descending.
Approach: with the destination at 4,000 m visibility, BKN008 and TEMPO 1,500 m, I cannot assume VMC. The disciplined course is to arrive overhead at the expected approach time, and if the weather is at or above the approach minima, commence the approach; if not, or if the approach cannot be completed, proceed to the alternate. Lost comms does not license a descent below minima.
2. Do the fuel arithmetic and state whether fuel or weather drives the decision.
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Final reserve 45 min at the hold burn of 1,100 kg/h = 825 kg. Usable for flight = 3,000 − 825 = 2,175 kg, which at 1,150 kg/h is 1 h 53 min of cruise.
To Mombasa: 210 nm at roughly 420 kt ground speed is 30 min, about 575 kg. Fuel overhead Mombasa ≈ 2,425 kg, still well above the 825 kg reserve.
To Malindi after one approach at Mombasa: say 15 min for the approach and go-around plus 50 nm (about 12 min) to Malindi - roughly 27 min, about 520 kg. Fuel at Malindi ≈ 1,900 kg, more than 1,000 kg above the final reserve.
The arithmetic is not tight, and that is the finding: fuel does not force the decision tonight. What it does mean is that I have no room for an extended hold; the reserve is a reserve, not holding fuel. So the decision is weather-driven, and I should make it early rather than orbit and let the fuel position become the constraint. If I elect to hold for the cell to clear, the hold time is bounded by the fuel above reserve - about 1 h 15 min at FL140 - and the 15 kt eastward movement says the line will be over Mombasa well before that.
3. How do you deal with the line of cells, and what would you do about the lack of radio contact while deviating?
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The tops above FL400 rule out the obvious option: there is no overflying this, and at FL300 there is no altitude in the aircraft's envelope that clears it. The choices are deviation or avoidance.
Deviation is normal control, but tonight it has a cost: a deviation off track without radio contact is exactly the situation in which ATC separation is built on predictability. The procedure protects me to a degree - 7600 and flying the last acknowledged clearance - but a turn toward the cells' south end over the water, or a hold 40 nm west of the line, takes me out of that predictability. Before leaving track I would try harder to raise someone: relay on 121.5, company frequency, and any aircraft on the TCAS display. If a relay is established, the deviation is coordinated and the problem is largely solved.
The cleaner option is the alternate. Malindi is CAVOK and lies north-east, clear of the line's immediate track for the moment, and going there keeps me on a predictable route with a known arrival in VMC where the light and visual signals can complete the communication. That is where the fuel and the weather point together.
What I would not do is press on to Mombasa through a gap in a line of embedded cells at night, with the destination already at 800 ft broken and thunderstorms overhead.