Airports, Air traffic control, and Airspace

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1.Airport signs and markings

There are six types of signs that may be found at airports. The more complex the layout of an airport, the more important the signs become to pilots. Appendix C of this publication shows examples of some signs that are found at most airports, their purpose, and appropriate pilot action. The six types of signs are:

Mandatory instruction signs—red background with white inscription. These signs denote an entrance to a runway, critical area, or prohibited area.

Location signs—black with yellow inscription and a yellow border, no arrows. They are used to identify a taxiway or runway location, to identify the boundary of the runway, or identify an instrument landing system (ILS) critical area.

Direction signs—yellow background with black inscription. The inscription identifies the designation of the intersecting taxiway(s) leading out of an intersection.

Destination signs—yellow background with black inscription and arrows. These signs provide information on locating areas, such as runways, terminals, cargo areas, and civil aviation areas.

Information signs—yellow background with black inscription. These signs are used to provide the pilot with information on areas that cannot be seen from the control tower, applicable radio frequencies, and noise abatement procedures. The airport operator determines the need, size, and location of these signs.

Runway distance remaining signs—black background with white numbers. The numbers indicate the distance of the remaining runway in thousands of feet.

A runway holding position sign is an airport version of a stop sign. It may be seen as a sign and/or its characters painted on the airport pavement. The sign has white characters outlined in black on a red background. It is always collocated with the surface painted holding position markings and is located where taxiways intersect runways. On taxiways that intersect the threshold of the takeoff runway, only the designation of the runway may appear on the sign. If a taxiway intersects a runway somewhere other than at the threshold, the sign has the designation of the intersecting runway. The runway numbers on the sign are arranged to correspond to the relative location of the respective runway thresholds.

Noncompliance with a runway holding position marking may result in the FAA filing a Pilot Deviation against you. Runway holding position markings consist of four yellow lines, two solid and two dashed, that are painted on the surface and extend across the width of the taxiway to indicate where the aircraft should stop when approaching a runway. These markings are painted across the entire taxiway pavement, are in alignment, and are collocated with the holding position sign as described above.  As you approach the runway, two solid yellow lines and two dashed lines will be visible. Prior to reaching the solid lines, it is imperative to stop and ensure that no portion of the aircraft intersects the first solid yellow line. Do not cross the double solid lines until a clearance from ATC has been received.  When the tower is closed or when operating at a non towered airport, you may taxi onto or across the runway only when the runway is clear and there are no aircraft on final approach. You should use extreme caution when crossing or taxiing onto the runway and always look both ways.  When exiting the runway, the same markings will be seen except the aircraft will be approaching the double dashed lines. In order to be clear of the runway, the entire aircraft must cross both the dashed and solid lines. An ATC clearance is not needed to cross this marking when exiting the runway.

At most towered airports, the enhanced taxiway centerline marking is used to warn you of an upcoming runway. It consists of yellow dashed lines on either side of the normal solid taxiway centerline and the dashes extend up to 150 feet prior to a runway holding position marking. They are used to aid you in maintaining awareness during surface movement to reduce runway incursions.

Runway numbers and letters are determined from the approach direction. The runway number is the whole number nearest one-tenth the magnetic azimuth of the centerline of the runway, measured clockwise from the magnetic north. In the case where there are parallel runways, the letters differentiate between left (L), right (R), or center (C).  For example, if there are two parallel runways, they would show the designation number and then either L or R beneath it. For three parallel runways, the designation number would be presented with L, C, or R beneath it.

A relocated runway threshold is used for construction or runway maintenance, to close only a portion of a runway. When a portion of a runway is closed, the runway threshold is relocated. It is referred to as a relocated threshold and methods for identifying the relocated threshold vary. A common way for the relocated threshold to be marked is a ten foot wide white bar across the width of the runway. When the threshold is relocated, the closed portion of the runway is not available for use by aircraft for takeoff or landing, but it can be used to taxi. When a threshold is relocated, it closes a portion of the approach end of a runway and it also shortens the length of the opposite direction runway. The yellow arrow heads are depicted across the width of the runway just prior to the threshold bar.

A displaced threshold is a threshold located at a point on the runway other than the designated beginning of the runway. Displacement of a threshold reduces the length of runway available for landings. The portion of runway behind a displaced threshold is available for takeoffs in either direction, or landings from the opposite direction. A ten feet wide white threshold bar is located across the width of the runway at the displaced threshold, and white arrows are located along the centerline in the area between the beginning of the runway and displaced threshold. White arrow heads are located across the width of the runway just prior to the threshold bar.  The instrument landing system (ILS) broadcasts signals to arriving instrument aircraft to guide them to the runway. Each of these ILSs have critical areas that must be kept clear of all obstacles in order to ensure quality of the broadcast signal.

At many airports, taxiways extend into the ILS critical area. Most of the time, this is of no concern; however, during times of poor weather, an aircraft on approach may depend on a good signal quality. When necessary, ATC will protect the ILS critical area for arrival instrument traffic by instructing taxiing aircraft to “hold short” of Runway (XX) ILS critical area.  The ILS critical area hold sign has white characters, outlined in black, on a red background and is installed adjacent to the ILS holding position markings. The holding position markings for the ILS critical area appear on the pavement as a horizontal yellow ladder extending across the width of the taxiway.  When instructed to “hold short of Runway (XX) ILS critical area,” you must ensure no portion of the aircraft extends beyond these markings. If ATC does not instruct you to hold at this point, then you may bypass the ILS critical area hold position markings and continue with your taxi.

Some taxiway stubs also have a runway safety area boundary sign that faces the runway and is visible to you only when exiting the runway. This sign has a yellow background with black markings and is typically used at towered airports where a controller commonly requests you to report clear of a runway. This sign is intended to provide you with another visual cue that is used as a guide to determine when you are clear of the runway safety boundary area.

2.Airport lighting

Airport beacons help a pilot identify an airport at night. The beacons are normally operated from dusk until dawn. Sometimes they are turned on if the ceiling is less than 1,000 feet and/or the ground visibility is less than 3 statute miles (VFR minimums). However, there is no requirement for this, so a pilot has the responsibility of determining if the weather meets VFR requirements. The beacon has a vertical light distribution to make it most effective from 1–10° above the horizon, although it can be seen well above or below this spread. The beacon may be an omnidirectional capacitor-discharge device, or it may rotate at a constant speed that produces the visual effect of flashes at regular intervals. The combination of light colors from an airport beacon indicates the type of airport. Some of the most common beacons are: Flashing white and green for civilian land airports, Flashing white and yellow for a water airport, Flashing white, yellow, and green for a heliport, and Two quick white flashes alternating with a green flash identifying a military airport.

Similar to runway lighting, taxiways also have various lights which help pilots identify areas of the taxiway and any surrounding runways.

Omnidirectional taxiway lights outline the edges of the taxiway and are blue in color. At many airports, these edge lights may have variable intensity settings that may be adjusted by an ATC when deemed necessary or when requested by the pilot. Some airports also have taxiway centerline lights that are green in color.

Clearance bar lights are installed at holding positions on taxiways in order to increase the conspicuity of the holding position in low visibility conditions. They may also be installed to indicate the location of an intersecting taxiway during periods of darkness. Clearance bars consist of three in-pavement steady-burning yellow lights.

Runway guard lights are installed at taxiway/runway intersections. They are primarily used to enhance the conspicuity of taxiway/runway intersections during low visibility conditions, but may be used in all weather conditions. Runway guard lights consist of either a pair of elevated flashing yellow lights installed on either side of the taxiway, or a row of in-pavement yellow lights installed across the entire taxiway, at the runway holding position marking.

Stop bar lights, when installed, are used to confirm the ATC clearance to enter or cross the active runway in low visibility conditions (below 1,200 ft Runway Visual Range (RVR)). A stop bar consists of a row of red, unidirectional, steady- burning in-pavement lights installed across the entire taxiway at the runway holding position, and elevated steady-burning red lights on each side. A controlled stop bar is operated in conjunction with the taxiway centerline lead-on lights which extend from the stop bar toward the runway. Following the ATC clearance to proceed, the stop bar is turned off and the lead-on lights are turned on. The stop bar and lead-on lights are automatically reset by a sensor or backup timer.

3.VASI

VASI installations are the most common visual glidepath systems in use. The VASI provides obstruction clearance within 10° of the extended runway centerline and up to four nautical miles (NM) from the runway threshold.  The VASI consists of light units arranged in bars. There are 2-bar and 3-bar VASIs. The 2-bar V ASI has near and far light bars and the 3-bar VASI has near, middle, and far light bars. Two-bar VASI installations provide one visual glidepath that is normally set at 3°. The 3-bar system provides two glidepaths, the lower glidepath normally set at 3° and the upper glidepath 1⁄4 degree above the lower glidepath.  The basic principle of the VASI is that of color differentiation between red and white. Each light unit projects a beam of light, a white segment in the upper part of the beam and a red segment in the lower part of the beam. The lights are arranged so the pilot sees the combination of lights to indicate below, on, or above the glidepath.

4.Airport Traffic Pattern

At airports without an operating control tower, a segmented circle visual indicator system, if installed, is designed to provide traffic pattern information. Usually located in a position affording maximum visibility to pilots in the air and on the ground and providing a centralized location for other elements of the system, the segmented circle consists of the following components: wind direction indicators, landing direction indicators, landing strip indicators, and traffic pattern indicators.

A tetrahedron is installed to indicate the direction of landings and takeoffs when conditions at the airport warrant its use. It may be located at the center of a segmented circle and may be lighted for night operations. The small end of the tetrahedron points in the direction of landing. Pilots are cautioned against using a tetrahedron for any purpose other than as an indicator of landing direction. At airports with control towers, the tetrahedron should only be referenced when the control tower is not in operation. Tower instructions supersede tetrahedron indications.

Landing strip indicators are installed in pairs and are used to show the alignment of landing strips. Traffic pattern indicators are arranged in pairs in conjunction with landing strip indicators and used to indicate the direction of turns when there is a variation from the normal left traffic pattern. (If there is no segmented circle installed at the airport, traffic pattern indicators may be installed on or near the end of the runway.)

At most airports and military air bases, traffic pattern altitudes for propeller-driven aircraft generally extend from 600 feet to as high as 1,500 feet above ground level (AGL). Pilots can obtain the traffic pattern altitude for an airport from the Chart Supplement U.S. (formerly Airport/Facility Directory). Also, traffic pattern altitudes for military turbojet aircraft sometimes extend up to 2,500 feet AGL. Therefore, pilots of en route aircraft should be constantly on alert for other aircraft in traffic patterns and avoid these areas whenever possible. When operating at an airport, traffic pattern altitudes should be maintained unless otherwise required by the applicable distance from cloud criteria according to Title 14 of the Code of Federal Regulations (14 CFR) part 91, section 91.155. Additional information on airport traffic pattern operations can be found in Chapter 4, “Air Traffic Control,” of the AIM. Pilots can find traffic pattern information and restrictions, such as noise abatement in the Chart Supplement U.S. (formerly Airport/Facility Directory).

These are the steps to entering the traffic pattern with a single runway in use.

1. Enter pattern in level flight, abeam the midpoint of the runway, at pattern altitude. (1,000' AGL is the recommended pattern altitude unless otherwise established.)

2. Maintain pattern altitude until abeam the approach end of the landing runway on downwind leg.
3. Complete turn to final at least 1⁄4 mile from the runway.
4. After takeoff or go-around, continue straight ahead until beyond departure end of runway.
5. If remaining in the traffic pattern, commence turn to crosswind leg beyond the departure end of the runway within 300 feet of pattern altitude.
6. If departing the traffic pattern, continue straight out, or exit with a 45° turn (to the left when in a left-hand traffic pattern; to the right when in a right-hand traffic pattern) beyond the departure end of the runway, after reaching pattern altitude.

These are the steps to entering the traffic pattern with parallel runways in use.

1. Enter pattern in level flight, abeam the midpoint of the runway, at pattern altitude. (1,000' AGL is the recommended pattern altitude unless otherwise established.)
2. Maintain pattern altitude until abeam approach end of the landing runway on downwind leg.
3. Complete turn to final at least 1⁄4 mile from the runway.
4. Do not overshoot final or continue on a track that penetrates the final approach of the parallel runway
5. After takeoff or go-around, continue straight ahead until beyond departure end of runway.

5.LAHSO

When simultaneous operations (takeoffs and landings) are being conducted on intersecting runways, Land and Hold Short Operations (LAHSO) may also be in effect. LAHSO is an ATC procedure that may require your participation and compliance. As pilot in command (PIC), you have the final authority to accept or decline any LAHSO clearance.  If issued a land and hold short clearance, you must be aware of the reduced runway distances and whether or not you can comply before accepting the clearance. You do not have to accept a LAHSO clearance. Pilots should only receive a LAHSO clearance when there is a minimum ceiling of 1,000 feet and 3 statute miles of visibility.  Runway holding position signs and markings are installed on those runways used for LAHSO. The signs and markings are placed at the LAHSO point to aid you in determining where to stop and hold the aircraft and are located prior to the runway/runway intersection.  The holding position sign has a white inscription with black border around the numbers on a red background and is installed adjacent to the holding position markings. If you accept a land and hold short clearance, you must comply so that no portion of the aircraft extends beyond these hold markings.  If receiving “cleared to land” instructions from ATC, you are authorized to use the entire landing length of the runway and should disregard any LAHSO holding position markings located on the runway. If you receive and accept LAHSO instructions, you must stop short of the intersecting runway prior to the LAHSO signs and markings.

6.Wake Turbulence

All aircraft generate wake turbulence during flight. This disturbance is caused by a pair of counter-rotating vortices trailing from the wingtips. The vortices from larger aircraft pose problems to encountering aircraft. The wake of these aircraft can impose rolling moments exceeding the roll- control authority of the encountering aircraft. Also, the turbulence generated within the vortices can damage aircraft components and equipment if encountered at close range. For this reason, a pilot must envision the location of the vortex wake and adjust the flight path accordingly.

Lift is generated by the creation of a pressure differential over the wing surface. The lowest pressure occurs over the upper wing surface and the highest pressure under the wing. This pressure differential triggers the rollup of the airflow aft of the wing resulting in swirling air masses trailing downstream of the wingtips. After the rollup is completed, the wake consists of two counter rotating cylindrical vortices. Most of the energy lies within a few feet of the center of each vortex.  Wake turbulence has historically been thought of as only a function of aircraft weight, but recent research considers additional parameters, such as speed, aspects of the wing, wake decay rates, and aircraft resistance to wake, just to name a few. The vortex characteristics of any aircraft will be changed with the extension of flaps or other wing configuration devices, as well as changing speed. However, as the basic factors are weight and speed, the vortex strength increases proportionately with an increase in aircraft operating weight or decrease in aircraft speed. The greatest vortex strength occurs when the generating aircraft is heavy, slow, and clean, since the turbulence from a “dirty” aircraft configuration hastens wake decay.  Trailing vortices have certain behavioral characteristics that can help a pilot visualize the wake location and take avoidance precautions. Vortices are generated from the moment an aircraft leaves the ground (until it touches down), since trailing vortices are the byproduct of wing lift. The vortex circulation is outward, upward, and around the wingtips when viewed from either ahead or behind the aircraft. Tests with large aircraft have shown that vortices remain spaced a bit less than a wingspan apart, drifting with the wind, at altitudes greater than a wingspan from the ground. Tests have also shown that the vortices sink at a rate of several hundred feet per minute, slowing their descent and diminishing in strength with time and distance behind the generating aircraft.  When the vortices of larger aircraft sink close to the ground (within 100 to 200 feet), they tend to move laterally over the ground at a speed of 2–3 knots. A crosswind decreases the lateral movement of the upwind vortex and increases the movement of the downwind vortex. A light quartering tailwind presents the worst case scenario as the wake vortices could be all present along a significant portion of the final approach and extended centerline and not just in the touchdown zone as typically expected. 

The following procedures are in place to assist pilots in vortex avoidance in the given scenario.

●      Landing behind a larger aircraft on the same runway— stay at or above the larger aircraft’s approach flight path and land beyond its touchdown point.

●      Landing behind a larger aircraft on a parallel runway closer than 2,500 feet—consider the possibility of drift and stay at or above the larger aircraft’s final approach flight path and note its touchdown point.

●      Landing behind a larger aircraft on the crossing runway— cross above the larger aircraft’s flight path.

●      Landing behind a departing aircraft on the same runway—land prior to the departing aircraft’s rotating point.

●      Landing behind a larger aircraft on a crossing runway—note the aircraft’s rotation point and, if that point is past the intersection, continue and land prior to the intersection. If the larger aircraft rotates prior to the intersection, avoid flight below its flight path. Abandon the approach unless a landing is ensured well before reaching the intersection.

●      Departing behind a large aircraft—rotate prior to the large aircraft’s rotation point and climb above its climb path until turning clear of the wake.

●      For intersection takeoffs on the same runway— be alert to adjacent larger aircraft operations, particularly upwind of the runway of intended use. If an intersection takeoff clearance is received, avoid headings that cross below the larger aircraft’s path.

●      If departing or landing after a large aircraft executing a low approach, missed approach, or touch-and-go landing (since vortices settle and move laterally near the ground, the vortex hazard may exist along the runway and in the flight path, particularly in a quartering tailwind), it is prudent to wait at least 2 minutes prior to a takeoff or landing.

●      En route, it is advisable to avoid a path below and behind a large aircraft, and if a large aircraft is observed above on the same track, change the aircraft position laterally and preferably upwind.

7.Collision Avoidance

Title 14 of the CFR part 91 has established right-of-way rules, minimum safe altitudes, and VFR cruising altitudes to enhance flight safety. The pilot can contribute to collision avoidance by being alert and scanning for other aircraft. This is particularly important in the vicinity of an airport.

Effective scanning is accomplished with a series of short, regularly spaced eye movements that bring successive areas of the sky into the central visual field. Each movement should not exceed 10°, and each should be observed for at least 1 second to enable detection. Although back and forth eye movements seem preferred by most pilots, each pilot should develop a scanning pattern that is most comfortable and then adhere to it to assure optimum scanning. Even if entitled to the right-of- way, a pilot should yield if another aircraft seems too close.

The following procedures and considerations are in place to assist pilots in collision avoidance under various situations:

• Before takeoff—prior to taxiing onto a runway or landing area in preparation for takeoff, pilots should scan the approach area for possible landing traffic, executing appropriate maneuvers to provide a clear view of the approach areas.

• Climbs and descents—during climbs and descents in flight conditions that permit visual detection of other traffic, pilots should execute gentle banks left and right at a frequency that permits continuous visual scanning of the airspace.

• Straight and level—during sustained periods of straight-and-level flight, a pilot should execute appropriate clearing procedures at periodic intervals.

• Traffic patterns—entries into traffic patterns while descending should be avoided.

• Traffic at VOR sites—due to converging traffic, sustained vigilance should be maintained in the vicinity of VORs and intersections.

• Training operations—vigilance should be maintained and clearing turns should be made prior to a practice maneuver. During instruction, the pilot should be asked to verbalize the clearing procedures (call out “clear left, right, above, and below”).

High-wing and low-wing aircraft have their respective blind spots. The pilot of a high-wing aircraft should momentarily raise the wing in the direction of the intended turn and look for traffic prior to commencing the turn. The pilot of a low- wing aircraft should momentarily lower the wing and look for traffic prior to commencing the turn.

A pilot deviation (PD) is an action of a pilot that violates any Federal Aviation Regulation. While PDs should be avoided, the regulations do authorize deviations from a clearance in response to a traffic alert and collision avoidance system resolution advisory. You must notify ATC as soon as possible following a deviation.

Pilot deviations can occur in several different ways. Airborne deviations result when a pilot strays from an assigned heading or altitude or from an instrument procedure, or if the pilot penetrates controlled or restricted airspace without ATC clearance.

To prevent airborne deviations, follow these steps:

●      Plan each flight—you may have flown the flight many times before but conditions and situations can change rapidly, such as in the case of a pop-up temporary flight restriction (TFR). Take a few minutes prior to each flight to plan accordingly.

●      Talk and squawk—Proper communication with ATC has its benefits. Flight following often makes the controller’s job easier because they can better integrate VFR and IFR traffic.

●      Give yourself some room—GPS is usually more precise than ATC radar. Using your GPS to fly up to and along the line of the airspace you are trying to avoid could result in a pilot deviation because ATC radar may show you within the restricted airspace.
Ground deviations (also called surface deviations) include taxiing, taking off, or landing without clearance, deviating from an assigned taxi route, or failing to hold short of an assigned clearance limit. To prevent ground deviations, stay alert during ground operations. Pilot deviations can and frequently do occur on the ground. Many strategies and tactics pilots use to avoid airborne deviations also work on the ground.
Pilots should also remain vigilant about vehicle/pedestrian deviations (V/PDs). A vehicle or pedestrian deviation includes pedestrians, vehicles or other objects interfering with aircraft operations by entering or moving on the runway movement area without authorization from air traffic control. In serious instances, any ground deviation (PD or VPD) can result in a runway incursion. Best practices in preventing ground deviations can be found in the following section under runway incursion avoidance.

A runway incursion is “any occurrence in the airport runway environment involving an aircraft, vehicle, person, or object on the ground that creates a collision hazard or results in a loss of required separation with an aircraft taking off, intending to take off, landing, or intending to land.” It is important to give the same attention to operating on the surface as in other phases of flights. Proper planning can prevent runway incursions and the possibility of a ground collision. A pilot should always be aware of the aircraft’s position on the surface at all times and be aware of other aircraft and vehicle operations on the airport. At times, towered airports can be busy and taxi instructions complex. In this situation, it may be advisable to write down taxi instructions. The following are some practices to help prevent a runway incursion:

• Read back all runway crossing and/or hold instructions.

• Review airport layouts as part of preflight planning, before descending to land and while taxiing, as needed.

• Know airport signage.

• Review NOTAM for information on runway/taxiway closures and construction areas.

• Request progressive taxi instructions from A TC when unsure of the taxi route.

• Check for traffic before crossing any runway hold line and before entering a taxiway.

• Turn on aircraft lights and the rotating beacon or strobe lights while taxing.

• When landing, clear the active runway as soon as possible, then wait for taxi instructions before further movement.

• Study and use proper phraseology in order to understand and respond to ground control instructions.

• Write down complex taxi instructions at unfamiliar airports.

Approximately three runway incursions occur each day at towered airports within the United States. The potential that these numbers present for a catastrophic accident is unacceptable. The following are examples of pilot deviations, operational incidents (OI), and vehicle (driver) deviations that may lead to runway incursions.

Detailed investigations of runway incursions over the past 10 years have identified three major areas contributing to these events:

●      Failure to comply with ATC instructions

●      Lack of airport familiarity

●      Nonconformance with standard operating procedures
Clear, concise, and effective pilot/controller communication is paramount to safe airport surface operations. You must fully understand and comply with all A TC instructions. It is mandatory to read back all runway “hold short” instructions verbatim.
Taxiing on an unfamiliar airport can be very challenging, especially during hours of darkness or low visibility. A request may be made for progressive taxi instructions which include step by step taxi routing instructions. Ensure you have a current airport diagram, remain “heads-up” with eyes outside, and devote your entire attention to surface navigation per ATC clearance. All checklists should be completed while the aircraft is stopped. There is no place for non-essential chatter or other activities while maintaining vigilance during taxi.

There are three major factors that increase the risk of runway confusion and can lead to a wrong runway departure:

• Airport complexity

• Close proximity of runway thresholds • Joint use of a runway as a taxiway

Not only can airport complexity contribute to a runway incursion; it can also play a significant role in runway confusion. If you are operating at an unfamiliar airport and need assistance in executing the taxi clearance, do not hesitate to ask ATC for help. Always carry a current airport diagram and trace or highlight your taxi route to the departure runway prior to leaving the ramp.

If you are operating from an airport with runway thresholds in close proximity to one another, exercise extreme caution when taxiing onto the runway. Figure 14-49 shows a perfect example of a taxiway leading to multiple runways that may cause confusion. If departing on Runway 36, ensure that you set your aircraft heading “bug” to 360°, and align your aircraft to the runway heading to avoid departing from the wrong runway. Before adding power, make one last instrument scan to ensure the aircraft heading and runway heading are aligned. Under certain circumstances, it may be necessary to use a runway as a taxiway. For example, during airport construction some taxiways may be closed requiring re- routing of traffic onto runways. In other cases, departing traffic may be required to back taxi on the runway in order to utilize the full runway length.  Since inattention and confusion often are factors contributing to runway incursion, it is important to remain extremely cautious and maintain situational awareness (SA). When instructed to use a runway as a taxiway, do not become confused and take off on the runway you are using as a taxiway.

8.ATC Traffic Advisories

Radar equipped ATC facilities provide radar assistance to aircraft on instrument flight plans and VFR aircraft provided the aircraft can communicate with the facility and are within radar coverage. This basic service includes safety alerts, traffic advisories, limited vectoring when requested, and sequencing at locations where this procedure has been established. A TC issues traffic advisories based on observed radar targets. The traffic is referenced by azimuth from the aircraft in terms of the 12-hour clock. Also, distance in nautical miles, direction in which the target is moving, and type and altitude of the aircraft, if known, are given.

An example would be: “Traffic 10 o’clock 5 miles east bound, Cessna 152, 3,000 feet.” The pilot should note that traffic position is based on the aircraft track and that wind correction can affect the clock position at which a pilot locates traffic. This service is not intended to relieve the pilot of the responsibility to see and avoid other aircraft. In addition to basic radar service, terminal radar service area (TRSA) has been implemented at certain terminal locations. TRSAs are depicted on sectional aeronautical charts and listed in the Chart Supplement U.S. (formerly Airport/Facility Directory). The purpose of this service is to provide separation between all participating VFR aircraft and all IFR aircraft operating within the TRSA. Class C service provides approved separation between IFR and VFR aircraft and sequencing of VFR aircraft to the primary airport. Class B service provides approved separation of aircraft based on IFR, VFR, and/or weight and sequencing of VFR arrivals to the primary airport(s).

9.Transponders and Transponder Codes

The transponder is the airborne portion of the secondary surveillance radar system and a system with which a pilot should be familiar. The ATC radar beacon system cannot display the secondary information unless an aircraft is equipped with a transponder. A transponder is also required to operate in certain controlled airspace.  A transponder code consists of four numbers from 0 to 7 (4,096 possible codes). There are some standard codes or A TC may issue a four-digit code to an aircraft. When a controller requests a code or function on the transponder, the word “squawk” may be used. Additional information concerning transponder operation can be found in the AIM, Chapter 4.  The 4 important transponder codes that pilots are required to know are 1200 for VFR, 7700 for an emergency, 7600 for lost communications, and 75oo for a hijacking.

10.ATIS

The automatic terminal information service is a continuous broadcast of recorded non control information in selected high activity terminal areas.  This information is essential but routine and includes information about the latest weather sequence, active runways, and other pertinent remarks.  Ceilings are typically not broadcasted if they are above 5000 feet and visibility is usually not mentioned if it is more than 5 statute miles.

11.ATC Communications

After landing, you should contact ground control only when so instructed by the tower. A clearance to taxi to the active runway is a clearance to taxi via taxiways to the active runway.  You may not cross any runway along your taxi route unless specifically cleared by ATC to do so.  When cleared to a runway, you are cleared to that runway's runup area, but not onto the active runway itself.  "Line up and wait" is the instruction to taxi onto the active runway and prepare for takeoff, but not to take off.  When notifying the tower that you are ready for departure, you must inform the controller of your location so they can positively identify you before clearing you for takeoff. When departing from a runway intersection, identify both the runway and the intersection in your request.

12.Terminal Radar Programs

Terminal radar programs for VFR aircraft are classified as basic, TRSA, class C, and class B service.  Basic radar service provides safety alerts, traffic advisories, and limited vectoring on a workload-permitting basis. TRSA service provides sequencing and separation for all participating VFR aircraft operating within a terminal radar service area.  Terminal radar program participation is voluntary for VFR traffic. 

13.Airspace

Class A airspace is generally the airspace from 18,000 MSL up to and including flight level 60,000, including the airspace overlying the waters within 12 nautical miles of the coast of the 48 contiguous states and Alaska.  The operating rules and equipment that are required in Alpha airspace is an IFR clearance to enter and operate within class A airspace is mandatory, pilots must be also instrument rated to act as PIC of an airplane in class A airspace. There are no VFR weather minimums in Alpha Airspace because all aircraft are on IFR flight plans. 

Class B airspace is generally the airspace from the surface to 10,000 feet MSL surrounding the nation’s busiest airports.  The configuration of each class B airspace area is individually tailored and consists of a surface area and two or more layers.  It will look like an upside down wedding cake.  The operating rules and equipment that are required in Bravo airspace is an ATC clearance is required prior to operating within class B airspace, two-way radio communication capability is required,  an operating ATC 4096 code or mode S transponder and automatic altitude reporting equipment are required within and above the lateral limits of class B airspace and within 30 nautical miles of the primary airport.  ADSB out equipment that either operates on the frequency of 1090 MHz or operates using a universal access transceiver on the frequency of 978 MHz is required, and the PIC must be at least a private pilot but a student or recreational pilot certificate holder may fly solo in class B airspace only if they have met the requirements and an endorsement.  For IFR operations, an operable VOR is required in addition to a two-way radio and mode C transponder.  The maximum indicated airspeed authorized when operating an airplane in the airspace underlying class B airspace is 200 knots.  If the minimum safe airspeed for any particular operation is greater than the maximum airspeed prescribed in 14 CFR part 91, the airplane may be operated at that speed.  In such cases, pilots are expected to advise ATC of the airspeed that will be used.  The mode C veil is the airspace within 30 nautical miles of a class b primary airport from the surface up to 10,000 MSL.  Unless otherwise authorized by ATC aircraft operating within the airspace must be equipped with a mode C transponder and ADSB out equipment as required in class B airspace. 

Class C airspace surrounds airports that have an operational control tower, are serviced by a radar approach control, and have a certain number of IFR operations or passenger enplanements.  Class C airspace normally consists of a surface area with a 5 nautical mile radius that extends from the surface to 4000 feet AGL.  A shelf area with a 10 nautical mile radius that extends from 1200 feet to 4000 feet AGL. The outer area which is between 10 and 20 nautical miles from the primary class C airport is not considered class C airspace.  Radar services in this area are available but not mandatory.  Operating rules and equipment are two way radio communications must be established and maintained with ATC before entering and while operating in class C airspace, a 4096 code transponder with mode C capability, two way radio communication capability and ADSB out equipment that either operates on the frequency of 1090 MHz or operates using a UAT on the frequency of 978 MHz.  When departing from a satellite airport without an operating control tower pilots must contact ATC as soon as practicable after takeoff.  Unless otherwise authorized or required by ATC, the maximum indicated airspeed permitted when at or below 2500 feet AGL within 4 nautical miles of a class C or class D primary airport is 200 Knots. 

Class Delta airspace surrounds airports that have both operating control tower and weather services available not associated with class b and class c airspace.  Airspace at an airport with a part-time control tower is classified as Class D airspace only when the control tower is operating. When a part-time control tower at the primary airport in Class D airspace is not in operation, the airspace at the surface becomes either Class E or Class G with an overlying Class E area beginning at 700 ft. AGL. Class D airspace normally extends from the surface up to and including  2,500 ft. AGL. The lateral dimensions of Class D airspace are based on local needs.  The operating rules and equipment are two-way communications must be established and maintained with ATC prior to entering and while operating in Class D airspace, when departing from a non-towered satellite airport within Class D airspace, and pilots must establish and maintain two-way radio communication with the primary airport's control tower.  The primary airport is the airport for which the Class D is designated.  A satellite airport is any other airport within the Class D airspace area.

Class E airspace is any controlled airspace that is not Class A, B, C, or D airspace. Except for 18,000 ft. MSL (the floor of Class A airspace), Class E airspace has no defined vertical limit but extends upward from either the surface or a designated altitude to the overlying or adjacent controlled airspace.  In most areas, the Class E airspace base is 1,200 ft. AGL. In many other areas, the Class E airspace base is either the surface or 700 ft. AGL.  Some Class E airspace begins at an MSL altitude depicted on the charts instead of an AGL altitude.  The federal airways are Class E airspace areas. Unless otherwise specified, they extend upward from 1,200 ft. AGL to, but not including, 18,000 ft. MSL.  There are no minimum pilot certification requirements to operate under VR in Class E airspace. ADS-B Out equipment that either operates on the frequency of 1090 MHz or operates using a UAT on the frequency of 978 MHz is required in Class E airspace.  Above 10,000 ft. MSL over the 48 states and D.C., excluding airspace at and below 2,500 ft. AGL, and over the Gulf of Mexico at and above 3,000 ft. MSL within 12 NM of the coastline of the United States.

Class G airspace is airspace that has not been designated as class A,B,C, D, or E airspace.  Class G airspace exists beneath the floor of controlled airspace in areas where the controlled airspace does not extend down to the surface.  No minimum pilot certification or airplane equipment is required in class G airspace. When approaching to land at an airport without an operating control tower in class G airspace, pilots should make all turns to the left, unless otherwise indicated.

Except when operating under a special VFR clearance, you may not operate your airplane beneath the ceiling under VFR within the lateral boundaries of the surface areas of Class B, C, D, or E airspace designated for an airport when the ceiling is less than 1000 feet. You may not take off, land, or enter the traffic pattern of an airport in Class B, C. D or E airspace unless the ground visibility is at least 3 SM. If ground visibility is not reported, flight visibility must be at least 3 statute miles. With some exceptions, special VFR clearances can be requested in Class B, C, D, or E airspace areas. You must remain clear of clouds and have visibility of at least 1 Statute Miles.  Flight under special VFR clearance at night is only permitted if the pilot has an instrument rating and the aircraft is IFR equipped.  Special VFR is an ATC clearance obtained from the control tower. If there is no control tower, obtain the clearance from the appropriate air traffic control facility.

14.Radio Phraseology

When contacting a Flight Service Station to open, close, or file a flight plan, the proper call sign is the name of the FSS followed by "radio";for example McAlester Radio.  Civilian aircraft should state their aircraft call sign with the make or model aircraft. For example: Cessna 44WH or Baron 22D. When a make or model is used, the initial November is dropped from the call sign.  Pilots should state each digit of the call sign individually. For example: 6449U equals six, four, four, niner, Uniform. When calling out altitudes up to, but not including, 18,000 ft., state the separate digits of the thousands, plus the hundreds, if appropriate. For example: 4,500 ft. means four thousand five hundred.

15.ELTs and VHF/DF

Older ELTs transmit simultaneously on 121.5 and 243.0 MHz, while newer ELTs transmit on 406 MHz. For older ELTs, you can monitor either 121.5 or 243.0 MHz during flight and before shutdown (after landing) to ensure your ELT has not been activated. The manufacture, importation, or sale of 121.5 MHz ELTs is prohibited. However, this rule does not preclude the continued use and maintenance of 121.5 MHz ELTs that are installed on aircraft before the rule's effective date. The VHF/Direction Finder facility is a ground operation that displays the magnetic direction of the airplane from the station each time the airplane transmits a signal to it. In order to take advantage of VHF/DF radio reception for assistance in locating a position, an airplane must have both a VHF transmitter and a receiver. The transmitter and receiver are necessary to converse with a ground station having VHF/DF facilities. The transmitter is also needed to send the signal that the Direction Finder identifies in terms of magnetic heading from the facility.

16.Emergency Radio Frequency

Whenever a pilot encounters an emergency condition in an aircraft, they can obtain assistance simply by contacting the air traffic control facility or other agency in whose area of responsibility the aircraft is operating, stating the nature of the emergency, the pilot's intentions, and the assistance desired.  If the pilot is not in contact with ATC, they should broadcast on radio frequency 121.5.  If the pilot must make an emergency landing, they should set the transponder on 7700. The distress or urgency message should consist of the following: If distress, begin with "MAYDAY, MAYDAY, MAYDAY", If urgency, begin with "PAN-PAN, PAN-PAN, PAN-PAN", Station name or "any station", Aircraft identification and type, present position and heading (if lost, last known position, time, and heading since that position), nature of the emergency, and pilot's intentions and any requests.  Other information that may be broadcast with the previous items (depending on the situation) include the following: weather conditions (if applicable), altitude or flight level, fuel remaining in minutes, number of people on board, and any other useful information.

17.ATC Light Signals

In the absence of radio communications, the tower can communicate with you by light signals. Light signal meanings depend on whether you are on the ground or in the air. Acknowledge light signals in the air by rocking wings in daylight and blinking lights at night.  If your radio fails and you wish to land at a tower-controlled airport, remain outside or above the airport's traffic pattern until the direction and flow of traffic has been determined, then join the traffic pattern and maintain visual contact with the tower to receive light signals.

In the air, these are what these light gun signals mean. 

Steady green - cleared to land

Flashing green - return for landing

Steady red - give way to other aircraft and continue circling

Flashing red - airport unsafe, do not land

Alternating red and green - exercise extreme caution

On the ground, these are what these light gun signals mean. 

Steady green - cleared to take off

Flashing green - cleared to taxi

Steady red - stop

Flashing red - Taxi clear of the runway in use

Flashing white - return to the starting point on the airport