Perfect Circles

Stand at any training airfield anywhere in the world and you will see pilots practicing circuits. It is a truism that take-offs and landings are the most dangerous phases of flight, and circuits provide an efficient way of practicing important skills.

In fact, circuits encapsulate much of the pilot training syllabus: take-offs, climbs, climbing turns, medium level turns, straight and level, descending, descending turns, slow flight and landing.

We might start with a definition: a circuit is a standard airfield traffic path followed by aircraft when taking off or landing. In non-Commonwealth countries, circuits are called “patterns”. The use of a standard circuit is principally for safety; the risk of collision is reduced. There are two common types of circuits: rectangular (or square) and oval. Rectangular circuits have six (or arguably five) legs: departure, crosswind, downwind, base, final, and upwind (although some argue that upwind and departure are the same thing).

Oval circuits have the same legs, but the crosswind and base legs are transitional; you pass through those legs while turning from upwind to downwind and downwind to final. As the names imply, legs are named in relation to the direction of the wind.

Circuits also have a standard height. A common circuit height is 1000 ft above ground level, or 500 ft for helicopters. At large airports, the circuit height for airliners may be 2000 ft AGL. By default, circuits are left-hand, but local conditions (or multiple runways) can sometimes require right-hand circuits. Left-hand circuits are the default direction because it affords