Normal operation of a small airplane
in the vicinity of an aerodrome
requires adherence to the standard traffic pattern, described below. This is necessary because of the extremely high volume of air traffic in a very small space; if everyone is following the same plan it's easier to keep track of where everyone is.
>>>>>>>>> Wind Direction >>>>>>>>>>>>>>>>
| o~ |
+-<-Upwind--<- | -- Runway -- | ---<--Final--<---+
| ------------------------------------------- ^
| Crosswind Base |
v Abeam |
45-degree / entry
The normal traffic pattern begins and ends on the runway and has four legs. One nearly always chooses to operate from the runway most nearly aligned against the wind (in this case, runway 19 (see runway numbering)). Taking off and landing into the wind allows you to have the lowest possible ground speed for your air speed (which is determined by the type of aircraft).
From the runway, one flies along the extended runway centerline into the wind until one reaches an altitude of about 500 feet AGL. This is the upwind leg. Its purposes is to give you enough time and altitude to make a safe turn with adequate ground clearance. If you experience an engine failure on takeoff, you will immediately make a 180-degree turn and land on the runway you just took off from in the opposite direction (since there may be someone immediately behind you landing in the direction you took off from, this may be excessively exciting.)
At the end of the upwind leg you turn 90 degrees. Above we've shown a pattern with only left turns; this is called a "left pattern" and is the standard unless otherwise explicitly called out (in which case it's a "right pattern", the opposite.) This turn brings you onto crosswind, perpendicular to the runway, and you continue to climb.
The length of your crosswind leg is adjusted to put your downwind the right distance from the runway. The "right distance" is "far enough away to have time to turn, but close enough to land if your engine fails". Normally this means about 1000-2000' but it varies with aircraft and terrain.
At the end of your crosswind you make another 90-degree turn (left or right as appropriate) to your downwind, and continue to climb. Early in the downwind (or even in the crosswind if you're a high-performance aircraft) you should reach pattern altitude -- specified for each airport and runway but usually 1000' AGL. During the downwind you check all your instruments and settings.
When you're abeam the numbers -- that is, directly in line with the landing end of the runway -- you begin your descent by retarding power and, once your airspeed declines, adding flaps. You continue in the same direction.
Once you've descended to about 600' AGL or so, and are about 45 degrees off the end of the runway (that is, on the downwind intersecting an imaginary line 45 degrees off the runway heading), you turn 90 degrees again for your base leg. You contiue your descent. Because you are operating in the region of reversed command, you primarily adjust your power to control your sink rate and your pitch to adjust your airspeed. Your sink rate must be set so that you reach ground level at the end of the runway and your airspeed must match the required approach speed (and later, landing speed) for your aircraft.
Once you intersect the extended runway centerline you turn again onto your final approach. You contiue your descent while carefully adjusting course, power and pitch to get position the aircraft onto the end of the runway. This is much harder than it sounds (it took me about 200 landings to become decent at it).
Shortly before you reach the numbers (the touchdown zone or TDZ), you pitch up slightly to a level flight attitude. The is the flare and its purpose is to bring your airspeed down to an absolute minimum before touchdown. On touchdown you can either stop the aircraft and then exit the runway, or you can immediately take off again for another trip around the pattern -- the latter is called a "touch-and-go". Beginning flight students spend far more time than they might like circling the airport in this manner...
The 45 degree entry line shows how you would approach the airport to land if you were coming from elsewhere. You fly along the 45 degree entry line until you intercept the downwind at midfield and proceed from there.
It is imperative everyone in the area known where everyone else is so as to avoid hitting them (midair collisions are no fun). Therefore, (unless you're NORDO) you announce your position over the radio frequently, ideally once each leg (in practice, sometimes less often if traffic is light (but always at least once on downwind), or more often if traffic is heavy). The frequency usually used for this (at an uncontrolled airport) is called a CTAF or Common Traffic Advisory Frequency. At a controlled airport you will still ordinarily still fly a pattern, but you will do so under the direction of the tower (or they may give you different instructions).