by Jonathan M. Stern
Airport and Traffic Pattern Operations
Each runway is assigned an identifying number determined by the direction of alignment of the runway. For example, a runway aligned in a 213° direction is referred to as runway 21. The 213° is rounded down to 210° and the last 0 is omitted. A runway aligned on 36° is called runway 4, because 36° is rounded up to 40 degrees.
When an airport has more than one runway running in the same direction (parallel runways), the runways are also assigned left, right, and center labels. For example, San Francisco International Airport has runways 1R, 1L, 28L, and 28R.
Runways are generally selected for use based on the wind direction and velocity. Takeoffs and landings are made into the wind to reduce the ground speed necessary during takeoff and landing and to reduce the amount of runway necessary for each. Ideally, the wind blows straight down the runway, although there is almost always some degree of crosswind component.
A rectangular pattern is used with a particular runway to provide for the orderly flow of air traffic to and from the runway (see Figure 2.35).
Figure 2.35. The rectangular traffic pattern helps to provide for the orderly flow of traffic.
The pattern begins and ends over the runway. Each of the legs is assigned an identifying name. The leg aligned with the runway upon takeoff is called the upwind leg, because the aircraft taking off is flying upwind—into the wind.
A standard traffic pattern uses left turns. After turning left from the upwind leg, a pilot is on the crosswind leg. Another left turn places the aircraft on the downwind leg. The left turn from downwind is made onto base leg. Finally, the aircraft turning left from the base leg to line up with the landing runway is on the final approach leg. Traffic patterns are generally flown 800 to 1,000 feet above the airport elevation.
At airports with control towers, the controllers advise the pilots how and when to enter the pattern and when to takeoff and land. Likewise, while operating on the ground, a ground controller radios instructions of when and where to taxi and what taxi route to follow. In the event of two-way radio communications failure, control towers are equipped with special light guns (see Figure 2.36).
Figure 2.36. Tower controllers are trained in the use of light guns in the event of two-way radio communication failure.
Table 2.3 on the following page sets forth the meanings of different light gun signals.
At uncontrolled airports, those airports without control towers, the pilots are responsible for complying with local patterns and maintaining an orderly flow of traffic. Standard procedures are used for entering and exiting traffic patterns.
For example, a pilot who is leaving the traffic pattern should normally climb on the upwind leg until within 300 feet of pattern altitude and then make a left 45° turn and continue climbing out of the pattern. An aircraft entering the pattern should normally fly so it arrives at the midpoint of the downwind leg on a 45° intercept.
The following right-of-way rules are controlling both inside and outside the traffic pattern:
General: When weather conditions permit, regardless of whether an operation is conducted under instrument flight rules or visual flight rules, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft. When a rule of this section gives another aircraft the right of way, the pilot shall give way to that aircraft and may not pass over, under, or ahead of it unless well clear.
In Distress: An aircraft in distress has the right of way over all other air traffic.
Converging: When aircraft of the same category are converging at approximately the same altitude (except head-on, or nearly so), the aircraft to the other's right has the right of way. If the aircraft are of different categories
- A balloon has the right of way over any other category of aircraft
- A glider has the right of way over an airship, airplane, or rotor craft
- An airship has the right of way over an airplane or rotor craft
|Table 2.3 Light Gun Signals|
|Signal Color/-Type||Surface Meaning||Flight Meaning|
|Steady Green||Cleared for takeoff||Cleared to land|
|Flashing Green||Cleared to taxi||Return for landing (to be followed by steady green at proper time)|
|Steady Red||Stop||Give way to other aircraft and continue circling|
|Flashing Red||Taxi clear of runway in use||Airport unsafe; do not land|
|Flashing White||Return to starting point on airport||Not applicable|
|Alternating Red And Green||Exercise extreme caution||Exercise extreme coution|
However, an aircraft towing or refueling other aircraft has the right of way over all other engine-driven aircraft.
Approaching Head-On: When aircraft are approaching each other head-on, or nearly so, each pilot of each aircraft shall alter course to the right.
Overtaking: Each aircraft that is being overtaken has the right of way and each pilot of an overtaking aircraft shall alter course to the right to pass well clear.
Landing: Aircraft, while on final approach to land or while landing, have the right of way over other aircraft in flight or operating on the surface, except that they shall not take advantage of this rule to force an aircraft off the runway surface which has already landed and is attempting to make way for an aircraft on final approach. When two or more aircraft are approaching an airport for the purpose of landing, the aircraft at the lower altitude has the right of way, but it shall not take advantage of this rule to cut in front of another which is on final approach to land or overtake that aircraft.
Note: There are different rules that apply to operation of aircraft on water.