traffic patterns

https://forum.flyawaysimulation.com/forum/topic/21707/traffic-pattern/
https://forum.flyawaysimulation.com/forum/topic/21074/airport-legs/
https://forum.flyawaysimulation.com/forum/topic/12414/traffic-pattern-questions/

An airfield traffic pattern is a standard path followed by aircraft when taking off or landing.

Wind direction

All aircraft prefer to take off or land facing into the wind. This has the effect of reducing their speed over ground and hence reducing the distance required to perform either maneuver.

Many airfields have runways facing a variety of directions. A common scenario is to have two runways arranged at or close to 90 degrees to one another, so that aircraft can always find a suitable runway. Almost all runways are reversible, and aircraft use whichever runway in whichever direction is best suited to the wind. In light and variable wind conditions, the direction of the runway in use might change several times during the day.

The flight manuals of many aircraft may specify the maximum allowable crosswind component in which they are permitted to operate. Once that limit is exceeded, the aircraft either is not permitted to fly, or must use another runway direction which allows a more into-wind path to be used for takeoff and landing.

The exception to this rule is at Alpine airports, 'Altiports' where the runway is on a severe slope. In these instances, takeoffs are made downhill and landings uphill, with the slope aiding in acceleration and deceleration.

Layout

Trafic patterns can be defined as left-hand or right-hand, according to which way the turns in the pattern lie. They are usually left-hand because most small airplanes are piloted from the left seat (or the senior pilot or pilot in command sits in the left seat), and so the pilot has better visibility out the left window. Right-hand patterns will be set up for parallel runways, for noise abatement or because of ground features (such as terrain, towers, etc.). Helicopters are encouraged, but not required, to use an opposite pattern from fixed wing traffic due to their slower speed and greater maneuverability. Because the active runway is chosen to meet the wind at the nearest angle (upwind), the circuit orientation also depends on wind direction. Patterns are typically rectangular in basic shape, and include the runway along one long side of the rectangle. Each leg of the pattern has a particular name:

* The section extending from the runway ahead is called the climb out or upwind leg.
* The first short side is called the crosswind leg.
* The long side parallel to the runway but flown in the opposite direction is called the downwind leg.
* The short side ahead of the runway is called the base leg.
* The section from the end of base leg to the start of the runway is called the final approach or finals.
* The area of the airfield adjacent to the runway but opposite the circuit is known as the dead side.

At an airport, the pattern (or circuit in the Commonwealth of Nations) is a conventional standard path for coordinating air traffic. It differs from so-called "straight in approaches" and "direct climb outs" in that aircraft using a traffic pattern remain in close proximity to the airport. Patterns are usually employed at small general aviation (GA) airfields and military airbases. Most large airports avoid the system, unless there is GA activity as well as commercial flights. However, a pattern of sorts is used at airports in some cases, such as when an aircraft is required to go around.

While many airfields operate a completely standard pattern, in other cases it will be modified according to need. For example, military airfields often dispense with the crosswind and base legs, but rather fly these as circular arcs directly joining the upwind and downwind sections.

An aircraft taking off will usually be expected to follow the circuit in use, and one arriving at the field to land will be expected to join the circuit in an orderly fashion before landing. This is often accomplished by entering the downwind leg at a 45 degree or 90 degree angle abeam midfield, or by using an overhead join, or sometimes by high-performance types with a run-and-break. Aircraft are expected to join and leave the circuit in an orderly and safe manner. Sometimes this will be at the discretion of the pilot, while at other times the pilot will be directed by air traffic control.

There is also a procedure known as an orbit which is where an aircraft flies a 360 loop either clockwise or anticlockwise. This is usually for separation with other circuit traffic, and can be the result of a controllers instruction, else the pilot will report e.g. "G-LL making 1 left-hand orbit, will advise complete".

Contra-rotating circuit patterns

In cases where two or more parallel runways are in operation concurrently, the aircraft operating on the outermost runways are required to perform their patterns in a direction which will not conflict with the other runways. Thus, one runway may be operating with a left-hand pattern direction, and the other one will be operating with a right-hand pattern direction. This allows aircraft to maintain maximum separation during their patterns, however it is important that the aircraft do not stray past the centerline of the runway when joining the final leg, so as to avoid potential collisions. If 3 or more parallel runways exist, as is the case at Bankstown Airport in Australia, then the middle runway(s) can, for obvious reasons, only be used when either a straight in approach is used or when the aircraft joins the pattern from a very wide base leg.

An airfield will define a circuit height or pattern altitude, that is, a nominal level above the field at which pilots are required to fly while in the circuit. Unless otherwise specified, the standard pattern height is 1000 ft above ground level, although a pattern height of 800 feet above ground level is relatively common. Helicopters usually fly their pattern at 500 feet above ground level.

The use of a pattern at airfields is for air safety. Rather than have aircraft flying around the field in a haphazard fashion, by using a pattern pilots will know from where to expect other air traffic, and be able to see it and avoid it. GA pilots flying under Visual Flight Rules (VFR) will not be separated by air traffic control, and so the pattern is a vital way to keep things orderly.

A pilot undergoing training will often fly many patterns, one after another. Usually, each landing is followed immediately by a take off and further pattern; this is called a touch and go, or roller.

Helicopters also prefer to land facing the wind and are often asked to fly a pattern on arrival or departure. Many airfields operate a special pattern for helicopters to take account of their low airspeed. This is usually a mirror image of the fixed-wing pattern, and often at a slightly lower standard height above surface level; as noted above this altitude is usually 500 feet above ground level.

👍 Very nice Tartanaviation, I couldn't have given a better answer.

CRJCapt wrote:

👍 Very nice Tartanaviation, I couldn't have given a better answer.

Indeed. I was just gonna tell him he needed to take the FS09 Flight Lessons. . . 😉

Ed

i second CRJcapt