VFR Weather Minima in Controlled Airspace

Why it matters

Visual flight rules only work if you can see: see the ground to navigate, see other aircraft in time to give way, see the terrain in time to avoid it. The weather minima are the legal definition of "enough to see". In controlled airspace they are also what lets ATC mix IFR traffic descending through cloud with VFR traffic staying out of it — the controller separates IFR aircraft from each other, and counts on every VFR aircraft remaining far enough from cloud that nobody bursts out of a cloud base into a windshield.

The numbers in this unit are among the most-tested facts on the PPAER, and the pattern continues on the PSTAR. Learn them as a picture, not a list.

The three conditions in controlled airspace

CAR 602.114 makes VFR flight in controlled airspace legal only when all of the following hold:

• the aircraft is flown with visual reference to the surface;
• flight visibility is at least 3 miles; and
• the aircraft stays at least 500 feet vertically and 1 mile horizontally from cloud.

"Visual reference to the surface" means you can actually see the ground or water and use it — a solid deck below you kills VFR in controlled airspace even in perfect sunshine on top (the over-the-top exception is a separate rating, covered later in this chapter).

Visibility in the CARs is always in statute miles, and the distance figures pair up asymmetrically on purpose: cloud directly above you hides descending traffic, so the vertical buffer is tight but mandatory; cloud beside you hides converging traffic that closes much faster, so the lateral buffer is a full mile.

Flight visibility versus ground visibility

Two different measurements appear in the minima, and the exam loves the difference:

• Flight visibility is what you see forward from the cockpit in flight. It is the pilot's own estimate, and it is the visibility that the 3-mile rule regulates everywhere in controlled airspace.
• Ground visibility is what a weather observer reports at an aerodrome (in a METAR, for instance). It only enters the rules where a reporting station exists.

Extra rules inside a control zone

A control zone is controlled airspace wrapped around an aerodrome, so CAR 602.114 adds two conditions there:

• when ground visibility is reported, it must be at least 3 miles, in addition to your own 3 miles of flight visibility; and
• except when taking off or landing, the aircraft must stay at least 500 feet above the surface.

The second point works together with cloud clearance: to be 500 feet above the ground and 500 feet below cloud, you need a ceiling of at least 1,000 feet. That is why a "1,000-foot ceiling and 3 miles" rule of thumb circulates for VFR in a control zone — the CARs never state it in those words, but the arithmetic produces it.