Traffic Pattern, Description
1. What is the pattern (or circuit, as it's known in some countries)?
The “pattern” or “traffic pattern” is a rectangular track adjacent to the runway, laid out so that the runway forms the middle section of one side of the rectangle. Pilots arriving or departing fly along this track at a standard altitude, typically 600 or 800 feet above the level of the runway.
There are two benefits to this. First, it tends to give a systematic approach to takeoffs and landings, and second, pilots know where to look for other planes that may be near the field.
Because all planes in the pattern fly at the same altitude, a pilot at pattern altitude can expect to see another plane in the pattern at a level very near the horizon. This avoids having to look “way up” or “way down” when trying to locate another plane. But, it is good practice to always keep a sharp eye out for planes both above and below pattern altitude.
A single strip of asphalt is actually two runways, in opposite directions. Runways are numbered according to the approximate compass heading the plane will have while taking off or landing. For example, Runway 3 will correspond to a heading of 30 degrees. Runway 12 corresponds to 120 degrees. (That is, drop the zero.)
The “other end” of Runway 3 will be Runway 21 (add 180 degrees). The other end of Runway 12 will be 30. A runway oriented exactly North-South will be designated 18 and 36.
The complete pattern
The pattern, laid out for both runway directions, forms a larger rectangle of twice the width, with the runway located on a line drawn through the center of the rectangle. However, only one-half of the complete pattern will be in use at a given time.
The term “active runway” refers to the direction currently being used for takeoffs and landings. A pilot arriving at the field, while still several miles out, may make a radio call like, “What's your active and reported traffic?” With this information, the pilot can then plan the entry into the pattern and be on the lookout for other planes in the area.
Size of the pattern
The actual size of the rectangular track is not standardized, being subject to the preference of the pilot. Early on, conventional wisdom held that the pattern should be flown close enough to the runway so that, in the event of engine failure, the pilot could glide to the runway.
However, with increased engine reliability, this has given way to other considerations having more to do with time, distance, and the comfort level of the pilot. Things will happen more quickly in a tight pattern flown close to the runway as opposed to a wide pattern with much longer legs on all four sides. The size of the preferred pattern also will depend upon the size, speed, and complexity of the plane.
Left-hand vs. Right-hand traffic
There is a choice to be made in deciding which way traffic should proceed around the pattern. The most common is Left-Hand Traffic in which all turns in the pattern are made to the left. In Right-Hand Traffic, all turns are made to the right. This will be established for each runway at a given location and is one of the things a pilot must learn before going into an unfamiliar airport.
In most cases, the same traffic direction will be used for both runway directions. However, terrain or obstructions may produce a situation where, for example, Runway 6 uses left-hand traffic but Runway 24 uses right-hand traffic.
2. Names of Pattern Legs, Turns, and Positions
Suppose we take off from a runway and fly around the pattern. We take off into the wind. The names of the legs as we encounter them are as follows:
Pilots frequently are asked for their position by other aircraft. Here are typical responses with explanations:
“Downwind for 24, midfield”
“Downwind for 24, opposite the numbers”
“Short final, runway 24”
“Crossing midfield, altitude 1800 feet”
“Turning crosswind, Runway 24”
“Turning downwind, Runway 24”
“Turning base, Runway 24”
“Turning final, Runway 24”
The two ends of a runway also have names:
Approach end of Runway 24:
Departure end of Runway 24:
3. Entering the Pattern
A pilot arriving at an airport and intending to land must first enter the pattern which will then take the plane to the touchdown point. Several “favored” ways to enter the pattern are described here.
45 degree to downwind leg
This is convenient when approaching the runway from the same side as the downwind leg of the active runway. While still a mile or so from the runway, the pilot positions the plane so that when its track points directly at the center of the runway, the plane will be flying at a 45 degree angle to the downwind leg. It is preferred that the pilot be at pattern altitude at this point.
While approaching the downwind leg, the pilot should look carefully for other planes in the pattern. Especially, look for planes on the crosswind leg, or perhaps for a plane making the turn from crosswind onto the downwind leg. These are the ones most likely to create a conflict. They may appear below the horizon if they have not yet reached pattern altitude.
At the proper distance from the runway, the pilot makes a 45 degree turn to the right (for left traffic) to join the downwind leg.
Straight in to join the downwind leg
If the pilot is approaching the field in the direction exactly opposite to the direction in which the plane will be landing, a straight-in path to the downwind leg is appropriate.
Another plane just climbing out from the runway or perhaps one on the crosswind leg are most likely to come in conflict. Also, be on guard for a plane making a 45 degree entry to the same downwind leg. Look carefully, both at pattern altitude and above because the other plane may be higher but descending to pattern altitude.
Straight in to join the base leg
It is not absolutely essential to fly a downwind leg if the pilot is approaching the field from a direction that would make it convenient to enter the base leg directly. However, this represents an abbreviated pattern, and the piloting chores usually done on the downwind leg must now be done on base. This is usually not a problem because the base leg can be much longer, essentially as long as one wishes.
Look for traffic, especially in two different places where conflict is likely. (1) Planes coming downwind for the same runway. (2) Planes making a long final approach. Either of these may intersect your flight path at right angles.
Straight in onto final approach
This is convenient if you are approaching the field more or less in line with the active runway, but it is one of the least favored because of the rapidity with which you approach the field. The other pattern entries at least get you close enough to the field to enable looking around a bit before taking the plunge onto final approach.
Be on guard for traffic on base leg that may turn onto final in front of you, or on top of you.
Cross mid-field followed by a turn onto downwind leg
If you are approaching the field from the side opposite that where the pattern for the active runway lies, you may choose to cross directly over the field and then turn directly onto the downwind leg.
If you choose this entry, look for traffic that may have just turned onto downwind from the crosswind leg, and also, check carefully for a plane that may be making a 45 degree entry onto downwind. It is likely that the plane making the “entry on a 45” will be harder to spot, but at the same time, your rate of closure for this plane will be greater.
Also, as you fly toward a point directly over the field, you will cross the downwind leg of the pattern for the opposite runway. Be sure to check for traffic in this area because someone may be planning to land in the wrong direction, or at least in the direction opposite to that you are planning. Mixups occur. Things happen.
An alternative procedure is to fly over the field at well above pattern altitude, get to the other side of the runway, go out a bit, descend to pattern altitude, and then make a 45 degree entry to the downwind leg. This procedure is preferred when traffic density is high.
Descending into the pattern
It is sometimes tempting to fly over the field at an altitude well above pattern and then descend rather steeply in a turn onto the downwind leg. This is not a preferred procedure because: (1) The pilot's visibility below the nose of the plane is usually restricted; and (2) because the pilot is above pattern altitude, other planes at pattern altitude will appear below the horizon and may not be seen because of ground clutter.
There is no law against this, but keep in mind that descending into the pattern involves greater risks, and descending turns into the pattern even more so.
4. Departing the Pattern
Generally speaking, leaving the pattern is a much less tense affair than entering. After all, when leaving, you are flying away from where the planes are thickest. Here are some favored departures:
Straight out from the active runway
This is the least exciting as it requires no turns and is convenient when your course to destination is nearly inline with the runway. Just climb out on departure leg and keep on going.
Course to pattern side of runway
Climb out on departure leg and make the crosswind turn. This will put you to within less than 90 degrees of your desired direction. Continue the climb as desired. Turn on course after you are clear of the pattern.
The advantage of making the crosswind turn is that it keeps you where other pilots expect you to be.
While on the crosswind leg, be sure to look for any traffic that may be making a straight-in approach to the downwind leg.
Course to side of runway opposite the pattern
Climb out on departure leg and make the crosswind turn. Continue to climb as desired. Turn downwind and then circle back over the runway to take up the desired heading.
Climbing out of the pattern is looked upon with more favor than descending into the pattern because the pilot can see planes above easier than planes below.
Avoid turns opposite to the traffic pattern
Suppose we're taking off on a runway headed due west (Runway 27, left traffic) and our course is to the northwest, say, to a compass heading of 320 degrees. It is very tempting to climb out on the departure leg to the point where you would normally make the crosswind turn, and then turn right on course.
If you do this, what are you in effect doing? Making a turn that takes you against the flow of traffic in the pattern for the opposite runway. You can easily meet someone face to face making the turn from base to final in the opposite direction.
So how can you make the turn safely? Fly straight out on the departure leg until well clear of the pattern, then make the turn. Simple enough. However, even though you don't make an early turn, keep an eye out for the pilot turning base to final in the wrong direction ... as always.
5. Importance of Radio
It is hard to overstate the importance of radio communications between pilots at uncontrolled fields. The radio is without a doubt the best single piece of safety equipment that can be placed on a plane. But it is good only if you use it, and use it wisely.
Pilots use the radio to report their positions and intentions. Other pilots, listening in, can develop a fairly complete and accurate picture of the traffic situation at a given field. Only infrequently will you hear a confusion or miscommunication, and even less often, a conflict arises because of it.
This is not an attempt to explain radio technique and phraseology, but here are a few tidbits to get you started.
First of all, you must have an appropriate radio, meaning one that transmits and receives on the aviation frequencies, and hopefully does it well. Small hand-held units can be purchased for a few hundred dollars.
Then you must know the frequency assigned to the airport in question. This can be found on a sectional chart, from the Airport Facilities Directory, or from the database of a GPS unit. The most popular common traffic advisory frequency (CTAF) is 122.8 MHz. Two others often encountered are 122.7 and 122.9 MHz.
Not only is the radio used for position reports and so forth, but it also gets used for such things as requesting fuel, a parking spot, and other mundane items. Generally, communications are between (1) a plane and the base station or FBO office, such as when requesting fuel, or (2) between a plane and all other planes in the area (traffic).
When calling the base station, the word Unicom is used. When making a call to all the planes in the area, use the word Traffic. It might go something like this where a pilot flying a plane with registration number E009CG is at Davidson Country Airport:
You get the idea. Note in the second communication above, that the name of the airport was repeated at the end of the transmission. Many times a pilot will miss the airport name at the beginning, and if there is more than one airport in the area using the same frequency that also has a Runway 24 ... prevents a bit of confusion every now and then.
Here's an important point: always keep radio “chatter” to a minimum. It should be strictly business. A missed position report or call to traffic could initiate a series of events that lead to disaster.
Author: Doc Green