Special VFR and VFR Over-the-Top

Why it matters

Two situations catch real pilots regularly. First: the airport's weather sits just below VFR — say two and a half miles in light snow — and you only need to land or leave the zone. Second: a thin, flat overcast covers the whole route, but the sky above it is crystal clear and the destination is wide open. The CARs provide a controlled, limited exception for each: Special VFR for the first, VFR over-the-top for the second. Both come with strings attached, and the strings are exactly what gets examined.

Special VFR: below the minima inside a control zone

When weather in a control zone is below the 3-mile visibility of CAR 602.114, CAR 602.117 allows special VFR flight if all of these are true:

• flight visibility is at least 1 mile (½ mile for helicopters);
• the aircraft is flown clear of cloud and with visual reference to the surface at all times;
• you request and receive an authorization from ATC — it is never offered spontaneously; the request must come from the pilot; and
• when ground visibility is reported in the zone, it is at least 1 mile (½ mile for helicopters).

ATC will grant the authorization if aerodrome traffic permits — IFR arrivals and departures come first, which is why a Special VFR clearance can involve holding outside the zone.

Two more conditions matter for aeroplanes. The aircraft must carry radio equipment capable of maintaining communication with ATC — Special VFR is a coordinated operation, not a sneak-in. And at night, Special VFR for an aeroplane is only authorized for the purpose of landing at the destination aerodrome: you may use it to get in, never to depart or transit at night.

VFR over-the-top: cruising above the layer

A VFR pilot normally owes the surface constant visual reference. CAR 602.116 lifts that one requirement — and only that one — for the cruise portion of a day flight, if the pilot holds the VFR over-the-top rating (CAR 401.45) or higher qualification and the weather cooperates on every count:

• vertical distance from cloud of at least 1,000 feet;
• when flying between two layers, the layers are at least 5,000 feet apart;
• flight visibility at cruising altitude of at least 5 miles; and
• the destination forecast shows, for the arrival window, no broken, overcast or obscured layer below 3,000 feet above the planned flight altitude, ground visibility of 5 miles or more, and no thunderstorms or precipitation.

The arrival window is defined precisely: with a TAF, from 1 hour before to 2 hours after the estimated time of arrival (using the worst of any TEMPO, BECMG or PROB condition); with only an area forecast (FA/GFA), from 1 hour before to 3 hours after ETA.

Take-off and landing still happen in ordinary VFR conditions — over-the-top only covers the cruise in between. The aircraft must also carry the additional equipment of CAR 605.15 (gyroscopic instruments, an attitude indicator, radio navigation equipment and more), because losing sight of the ground makes the flight instrument-dependent in everything but name.