Special VFR decision with a lowering cloud base
You are PIC of a Cessna 172 (VFR-equipped, no IFR certification) on a private VFR flight from Plaisance (FIMP) to a grass strip 28 NM south. At 1430 local you are cruising at 3,500 ft AMSL. The 1400 METAR for FIMP gives wind 130/10, visibility 6 km in light rain, cloud few at 1,200 ft, broken at 1,800 ft, temperature 28°C, QNH 1014. The destination strip reports visibility 10 km and cloud base 3,000 ft. To remain VFR at 3,500 ft you need 8 km visibility and 1,500 m horizontal/300 m vertical cloud clearance (ICAO Annex 2 minima above 900 m AMSL). The broken layer top is not reported. Your route crosses a ridge at 1,600 ft, and the minimum safe altitude is 2,300 ft. ATC offers a Special VFR clearance back into the FIMP control zone, but your aircraft is not IFR-certified. You have 2 hours 10 minutes of fuel remaining; FIMP is 12 minutes away.
1. Is the flight legal VFR at 3,500 ft in the reported conditions? Justify with the visibility and cloud-clearance figures.
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At 3,500 ft AMSL (1,067 m) you are above 900 m, so the applicable ICAO VFR minima are 8 km flight visibility and 1,500 m horizontal/300 m vertical clearance from cloud. The reported visibility is 6 km, which is below 8 km. In addition, the aircraft is above a broken layer at 1,800 ft whose tops are not reported, so you cannot establish 300 m vertical clearance from cloud tops. Therefore the flight is not legal VFR at 3,500 ft. Remaining VFR by descending is not possible because the route MSA is 2,300 ft and the ridge rises to 1,600 ft; below 900 m the 1,200 ft cloud base would not allow 300 m vertical clearance either.
2. What are your realistic options, taking into account the ridge, MSA, fuel and aircraft certification? Which do you choose?
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Continuing VFR is rejected because visibility is 6 km against an 8 km requirement and cloud tops are unknown. Climbing is not an option: you are not IFR-certified and cannot guarantee cloud clearance. Descending below 900 m is blocked by the 2,300 ft MSA and the 1,600 ft ridge, and the cloud base would not give 300 m vertical clearance. Diverting to the destination strip VFR would still require crossing the ridge and maintaining VFR, which the present visibility does not allow. The practical option is to return to FIMP under Special VFR: it is 12 minutes away, you have 2 h 10 min fuel, and FIMP reports 6 km visibility and a 1,200 ft cloud base, which ATC can work with under SVFR. I would request SVFR back to FIMP rather than press on.
3. What conditions apply to the Special VFR clearance, and what would you tell ATC?
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SVFR is a VFR clearance in controlled airspace, not an IFR clearance. You must remain clear of cloud, keep at least the visibility ATC specifies, and comply with clearances; you cannot enter cloud or accept a clearance you cannot maintain. I would call: 'FIMP Approach, Cessna [callsign], 3,500 ft, 12 NM south, request Special VFR to FIMP, visibility 6 km, cloud base 1,200 ft, unable VFR, 2 hours 10 minutes fuel.' Then I would follow the clearance, report entering the control zone, and if the SVFR conditions cannot be met, turn away and land at a suitable aerodrome rather than press into cloud.