Aerodrome traffic pattern description[PDF]
Standard circuit parameters
The standard circuit parameters are:
- All turn angles are 90°.
- All turns shall be taken to the left: that’s left hand circuit.
- The circuit shall be performed at 1000ft above the ground (AGL) or airfield elevation.
- You have no charts of the airfield.
- Some parameters are not published on charts.
Parameters published on charts
Be careful, sometimes on charts, all or part of the parameters can be published:
- Circuit pattern form (angles of turn on some legs) cannot always be rectangular.
- Turn orientation can be left, right or both.
- Specific Altitude or height (AMSL or AGL) can be different than 1000ft AGL.
- Specific touchdown points.
Some situations, such as terrain, noise-sensitive areas, cities, natural parks, require all turns in the aerodrome traffic circuit to be made to the right. This is then called a right hand pattern.
It is not unusual to find a runway served by a standard (left) pattern when used in the one direction and by a right hand pattern in the opposite direction, thus the pattern will always be on the same side of the runway.
ATC:”D-ECHO, enter right downwind runway 34” This will be the right downwind of the runway.
Circuit pattern legs
- Upwind leg
- Crosswind leg
- Downwind leg
- Base leg
This chapter will study the circuit pattern legs with a light aircraft (step by step).
We will continue climbing straight ahead to gain sufficient altitude before the 90-degree turn to the crosswind leg. Notice that the upwind leg is identical for a standard and non-standard pattern.
You are now entering the traffic side of the circuit: watch for aircraft joining the circuit on crosswind or on beginning of downwind.
The crosswind leg is a flight path at a 90° angle to the take-off direction. After making a left turn from the upwind leg one enters the crosswind leg. This turn is made at a safe height, while the climb is continued towards the indicated or cleared circuit altitude.
The downwind leg is a flight path at a 180° angle (opposite) to the take-off direction.
The pilot must check the crosswind drift against selected landmarks and adjust heading to track parallel to the runway, perform the appropriate downwind cockpit checks and hold altitude and appropriate traffic spacing.
The downwind leg will be flown at moderate speed, adjusted to avoid overtaking preceding aircraft, and holding a constant height. He must set adequate power and trim the aircraft to maintain an airspeed which allows time to plan the landing without unnecessarily delaying other traffic – probably around 1.7 × Vso.
The pilot shall maintain visual separation with outside landmarks and keep the runway in sight. In the last third of the downwind, approach configuration is set.
The base leg is a flight path at a 90° angle to the landing runway direction and connects the downwind leg to the final approach leg. During base leg, the pilot initiates the descent to reach about 500ft AGL at the end of the leg.
The pilot holds airspeed but reduces power so that a descent is started.
The time spent flying the base leg is most important, providing the opportunity to set up the aircraft in the approach attitude:
- to establish a power and flap setting [and trim] for the required rate of descent
- to check for conflicting traffic both airborne and on the ground and particularly any traffic on a straight-in approach or very wide circuit;
- to assess the crosswind component along the landing path
- to decide the touchdown technique appropriate for the conditions and to review the pre-landing checks.
During final, the pilot prepares his plane for landing: flaps configuration, speed near 1.3 x Vso (stall speed).
The final approach leg is a flight path in the direction of landing from the base leg to the runway.
Summary of the traffic pattern
- Take off point on the runway
- End of climb out on upwind leg
- Crosswind leg
- Downwind leg
- Turning on base leg (end of downwind)
- Base leg
- Turning on final (end of base leg)
- Short final
- VID 150259 - Creation
- VID 435695 - Wiki integration
DATE OF SUBMISSION
- 06:23, 14 November 2019
- This documentation is copyrighted as part of the intellectual property of the International Virtual Aviation Organisation.
- The content of this documentation is intended for aviation simulation only and must not be used for real aviation operations.