VFR into IMC over the Zambezi Valley
You are flying a Cessna 172 (VFR only, no autopilot) from Tete (FQTT) to Quelimane (FQQL) at 6 500 ft. The forecast was CAVOK, but 40 NM east of Tete the visibility drops to about 3 km in haze with scattered cloud at 4 000 ft and rising terrain to the north. Your GPS shows Quelimane 120 NM ahead, Tete 40 NM behind, and a small airstrip at Moatize 15 NM to the south-west. Fuel is 120 L; burn is 34 L/h; reserve is 45 minutes (≈26 L). The cloud base is lowering and the haze is thickening ahead.
1. Assess your options and recommend a course of action.
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Situation. VFR-only aircraft, no autopilot, deteriorating visibility and lowering cloud, rising terrain to the north. Continuing east into worsening conditions is the classic 'VFR into IMC' trap.
Options:
- Continue to Quelimane - 120 NM ≈ 3.5 h at 34 L/h ≈ 120 L, which exceeds available fuel above reserve. Not viable.
- Return to Tete - 40 NM ≈ 1.2 h ≈ 40 L, leaving ~54 L above reserve. Viable and safe.
- Divert to Moatize - 15 NM ≈ 0.5 h ≈ 17 L, but the strip's condition, length and weather are unknown; only use if confirmed suitable and VMC.
Recommendation. Turn back to Tete now, while VMC is still available behind you. Climb is not an option (cloud base lowering). Advise ATC of the change, request current Tete weather, and land. Do not attempt to 'scud-run' or climb through cloud in a VFR-only aircraft.
2. What decision errors commonly lead to this situation, and how would you prevent them in future?
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Common errors:
- Plan continuation bias - pressing on because the destination is 'only 120 NM away'.
- Optimism about forecast - ignoring signs of deterioration.
- Fuel miscalculation - not checking fuel against the actual diversion.
- Get-there-itis - schedule pressure.
Prevention:
- Set personal minimums (visibility, cloud base, crosswind) and brief them before flight.
- Use in-flight decision points with pre-planned escape routes and alternates.
- Monitor weather at each waypoint and turn back early.
- Fuel planning with a clear reserve and diversion calculation before departure.
- CRM/ADM training - recognise and verbalise plan continuation bias.