Airports vary in complexity from small grass or sod  strips to major terminals having multiple paved runways  and taxiways. Regardless of the type of airport, the pilot  must know and abide by the rules and general operating  procedures applicable to the airport being used. These rules  and procedures are based not only on logic or common sense  but also on courtesy, and their objective is to keep air traffi c  moving with maximum safety and efficiency. The use of  any traffic pattern, service, or procedure does not alter the  responsibility of pilots to see and avoid other aircraft.  Generally, there are two types of airport operations: Airport operations is a prerequisite for reading and  understanding this chapter. The Pilot’s Handbook of  Aeronautical Knowledge (FAA-H-8083-25) chapter on  airport operations is the starting point for this subject.  Additionally, the portions of the Aeronautical Information  Manual (AIM) covering aeronautical lighting and other  airport visual aids, airspace, and air traffi c control, should  be studied prior to reading this chapter. The following airport patterns are applicable to both towered  and nontowered airport operations; however, in nontowered  airports the pilot should use the information presented in this  chapter along with the references provided in the summary to  coordinate with the other air traffic. When flying at towered  airports, the principles must be understood to understand  the air traffic controller’s instructions. The pilot is always  responsible for “see and avoid” and must continually look  for other aircraft in towered and nontowered operations. To assure that air traffi c flows into and out of an airport in  an orderly manner, an airport traffic pattern is established  appropriate to the local conditions, including the direction  and placement of the pattern, altitude to be fl own, and  procedures for entering and leaving the pattern. Unless the  airport displays approved visual markings indicating that  turns should be made to the right, pilots should make all  turns in the pattern to the left. When operating at an airport with an operating control tower,  the pilot receives by radio a clearance to approach or depart,  as well as pertinent information about the traffi c pattern. If  there is not a control tower, it is the pilot’s responsibility to  determine the direction of the traffic pattern, to comply with  the appropriate traffic rules, and to display common courtesy  toward other pilots operating in the area. The pilot is not expected to have extensive knowledge of  all traffic patterns at all airports; but if the pilot is familiar  with the basic rectangular pattern, it is easy to make proper  approaches and departures from most airports, regardless of  whether they have control towers. At airports with operating  control towers, the tower operator may instruct pilots to  enter the traffic pattern at any point or to make a straight- in approach without flying the usual rectangular pattern.  Many other deviations are possible if the tower operator and  the pilot work together in an effort to keep traffi c moving  smoothly. Jets or heavy aircraft frequently fly wider and/or  higher patterns than lighter aircraft and in many cases make  a straight-in approach for landing. The standard rectangular traffic pattern and terms are  illustrated in  Figure 10-1.  The terms of an airport in the  pattern after takeoff are described in  Figure 10-1.  Departure leg—the flightpath which begins after takeoff  and continues straight ahead along the extended runway  centerline.   Crosswind leg—a flightpath at right angles to the landing  runway off its takeoff end.   Downwind leg—a flightpath parallel to the landing runway  in the opposite direction of landing.   Base leg—a flightpath at right angles to the landing runway  off its approach end and extending from the downwind leg  to the intersection of the extended runway centerline (third  left hand 90° turn).  Final approach—a flightpath in the direction of landing  along the extended runway centerline from the base leg to  the runway.   Upwind leg—a fl ightpath parallel to the landing runway in  the direction of landing (not shown in  Figure 10-1 ).  The traffic pattern altitude is usually 1,000 feet above the  elevation of the airport surface; however, many airports use  different pattern altitudes for different types of aircraft. This  information can be found in the Airport/Facility Directory  (A/FD). The use of a common or known altitude at a given  airport is a key factor in minimizing the risk of collisions at  airports without operating control towers because aircraft can  be expected to be at a certain level making it easier to see.  Standard Airport Traffi c Patterns  Airport Operations •  Uncontrolled airports where there is no control  tower  •   Controlled airports where there is a control tower with  an air traffi c controller 10-2