Marginal VFR into Beira with a developing cumulus field
You are on a VFR flight from Quelimane to Beira at 3,500 ft, in a Cessna 172, in the late afternoon. The TAF for Beira calls for scattered cloud at 2,500 ft, broken at 4,000 ft, with a TEMPO for showers and broken cloud at 1,200 ft. Along track you see a line of developing cumulus with bases around 2,000 ft and tops building to 12,000 ft, and the ground beneath is obscured in places. Visibility outside the showers is 8 km, falling to 3 km in rain. The sun sets in 40 minutes. You have 1.5 hours of fuel remaining and Beira is 60 NM ahead (groundspeed 95 kt). There is no other suitable aerodrome between you and Beira.
1. Assess whether continuing VFR at 3,500 ft is legal and safe under these conditions.
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Legality. VFR minima in controlled airspace at 3,500 ft typically require 5 km flight visibility and 1,500 m horizontal / 300 m vertical (1,000 ft) cloud separation. With bases at 2,000 ft and tops to 12,000 ft, you cannot maintain 1,000 ft vertical separation from cloud while remaining clear of terrain and staying VFR. In the showers, visibility of 3 km already breaches the 5 km minimum. So the flight is not legally VFR in the affected areas.
Safety. The cloud is convective, building, and obscuring the ground. Bases are lowering. You are 60 NM out with 90 minutes of fuel - a 38-minute leg - so fuel is not the constraint; the weather is. Entering a building cumulus field with no alternate behind you and sunset in 40 minutes is the classic VFR-into-IMC trap.
Conclusion. Continuing as planned is not acceptable. You must change the plan now, while you still have options and daylight.
2. State, in order, the actions you would take and the decision criteria you would apply.
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Actions, in order.
- Turn back or divert immediately while you still have clear air behind you - the safest escape is the one you came from. Quelimane is behind you with known conditions.
- Call ATC and state your situation: position, altitude, intentions, and that you are unable to maintain VFR on the planned route. Ask for known traffic, actual reported conditions at Beira, and any suitable diversion.
- If you cannot turn back, descend only if you can maintain clear of cloud and terrain, and follow a ground feature (coast, road, railway) at a safe height. Do not climb into the cumulus.
- Prepare for the worst: note your position, brief a precautionary landing option, and set a hard decision point.
Decision criteria. The moment any of these is true, you divert or land: visibility below 5 km, inability to maintain 1,000 ft above cloud, ground contact lost, or sunset within your planned arrival margin. In this scenario at least two of those are already true. The correct answer is to divert now, not to press on and hope the field opens up.