Pilot's Handbook of Aeronautical Knowledge (Federal Aviation Administration)
Page 61
Figure 14-35. Runway Entrance Lights (REL).
Figure 14-36. Takeoff Hold Lights (THL).
Wind Direction Indicators
It is important for a pilot to know the direction of the wind. At facilities with an operating control tower, this information is provided by ATC. Information may also be provided by FSS personnel either located at a particular airport or remotely available through a remote communication outlet (RCO), or by requesting information on a CTAF at airports that have the capacity to receive and broadcast on this frequency.
When none of these services is available, it is possible to determine wind direction and runway in use by visual wind indicators. A pilot should check these wind indicators even when information is provided on the CTAF at a given airport because there is no assurance that the information provided is accurate.
The wind direction indicator can be a wind cone, wind sock, tetrahedron, or wind tee. These are usually located in a central location near the runway and may be placed in the center of a segmented circle, which identifies the traffic pattern direction if it is other than the standard left-hand pattern. [Figures 14-37 and 14-38]
The wind sock is a good source of information since it not only indicates wind direction but allows the pilot to estimate the wind velocity and/or gust factor. The wind sock extends out straighter in strong winds and tends to move back and forth when the wind is gusting. Wind tees and tetrahedrons can swing freely and align themselves with the wind direction. Since a wind tee or tetrahedron can also be manually set to align with the runway in use, a pilot should also look at the wind sock for wind information, if one is available.
Traffic Patterns
At airports without an operating control tower, a segmented circle visual indicator system, if installed, is designed to provide traffic pattern information. [Figure 14-38] 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. [Figure 14-38] 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).
Figure 14-37. Wind direction indicators.
Figure 14-38. Segmented circle.
Example: Key to Traffic Pattern Operations—Single Runway
1. Enter pattern in level flight, abeam the midpoint of the runway, at pattern altitude. (1,000’ AGL is recommended pattern altitude unless otherwise established.) [Figure 14-39]
2. Maintain pattern altitude until abeam approach end of the landing runway on downwind leg. [Figure 14-39]
3. Complete turn to final at least ¼ mile from the runway. [Figure 14-39]
4. After takeoff or go-around, continue straight ahead until beyond departure end of runway. [Figure 14-39]
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. [Figure 14-39]
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. [Figure 14-39]
Example: Key to Traffic Pattern Operations—Parallel Runways
1. Enter pattern in level flight, abeam the midpoint of the runway, at pattern altitude. (1,000’ AGL is recommended pattern altitude unless otherwise established.) [Figure 14-40]
2. Maintain pattern altitude until abeam approach end of the landing runway on downwind leg. [Figure 14-40]
3. Complete turn to final at least ¼ mile from the runway. [Figure 14-40]
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. [Figure 14-40]
Figure 14-39. Traffic pattern operations—single runway.
6. If remaining in the traffic pattern, commence turn to crosswind leg beyond the departure end of the runway within 300 feet of pattern altitude. [Figure 14-40]
7. 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. [Figure 14-40]
8. Do not continue on a track that penetrates the departure path of the parallel runway. [Figure 14-40]
Radio Communications
Operating in and out of a towered airport, as well as in a good portion of the airspace system, requires that an aircraft have two-way radio communication capability. For this reason, a pilot should be knowledgeable of radio station license requirements and radio communications equipment and procedures.
Radio License
There is no license requirement for a pilot operating in the United States; however, a pilot who operates internationally is required to hold a restricted radiotelephone permit issued by the Federal Communications Commission (FCC). There is also no station license requirement for most general aviation aircraft operating in the United States. A station license is required, however, for an aircraft that is operating internationally, that uses other than a VHF radio, and that meets other criteria.
Radio Equipment
In general aviation, the most common types of radios are VHF. A VHF radio operates on frequencies between 118.0 megahertz (MHz) and 136.975 MHz and is classified as 720 or 760 depending on the number of channels it can accommodate. The 720 and 760 use .025 MHz (25 kilohertz (KHz) spacing (118.025, 118.050) with the 720 having a frequency range up to 135.975 MHz and the 760 reaching up to 136.975 MHz. VHF radios are limited to line of sight transmissions; therefore, aircraft at higher altitudes are able to transmit and receive at greater distances.
In March of 1997, the International Civil Aviation Organization (ICAO) amended its International Standards and Recommended Practices to incorporate a channel plan specifying 8.33 kHz channel spacings in the Aeronautical Mobile
Service. The 8.33 kHz channel plan was adopted to alleviate the shortage of VHF ATC channels experienced in western Europe and in the United Kingdom. Seven western European countries and the United Kingdom implemented the 8.33 kHz channel plan on January 1, 1999. Accordingly, aircraft operating in the airspace of these countries must have the capability of transmitting and receiving on the 8.33 kHz spaced channels.
Using Proper Radio Procedures
Using proper radio phraseology and procedures contribute to a pilot’s ability to operate safely and efficiently in the airspace system. A review of the Pilot/Controller Glossary contained in the AIM assists a pilot in the use and understanding of standard terminology. The AIM also contains many examples of radio communications.
Figure 14-40. Traffic pattern operation—parallel runways.
ICAO has adopted a phonetic alphabet that should be used in radio communications. When communicating with ATC, pilots should use this alphabet to identify their aircraft. [Figure 14-41]
Lost Communication Procedures
It is possible that a pilot might experience a malfunction of the radio. This might cause the transmitter, receiver, or both to become inoperative. If a receiver becomes inoperative and a pilot needs to land at a towered airport, it is advisable to remain outside or above Class D airspace until the direction and flow of traffic is determined. A pilot should then advise the tower of the aircraft type, position, altitude, and intention to land. The pilot should continue, enter the pattern, report a position as appropriate, and watch for light signals from the tower. Light signal colors and their meanings are contained in Figure 14-42.
If the transmitter becomes inoperative, a pilot should follow the previously stated procedures and also monitor the appropriate ATC frequency. During daylight hours, ATC transmissions may be acknowledged by rocking the wings and at night by blinking the landing light.
When both receiver and transmitter are inoperative, the pilot should remain outside of Class D airspace until the flow of traffic has been determined and then enter the pattern and watch for light signals.
Radio malfunctions should be repaired before further flight. If this is not possible, ATC may be contacted by telephone requesting a VFR departure without two-way radio communications. No radio (NORDO) procedure arrivals are not accepted at busy airports. If authorization is given to depart, the pilot is advised to monitor the appropriate frequency and/or watch for light signals as appropriate.
Figure 14-41. Phonetic alphabet.
If radio communication is lost, it may be a prudent decision to land at a non-towered airport with lower traffic volume, if practical. When operating at a non-towered airport, no radio communication is necessary. However, pilots should be extra vigilant when not using the radio. Other traffic may not as easily be aware of your presence when they are expecting the standard radio calls.
Air Traffic Control (ATC) Services
Besides the services provided by an FSS as discussed in Chapter 12, “Aviation Weather Services,” numerous other services are provided by ATC. In many instances a pilot is required to have contact with ATC, but even when not required, a pilot may find their services helpful.
Primary Radar
Radar is a device that provides information on range, azimuth, and/or elevation of objects in the path of the transmitted pulses. It measures the time interval between transmission and reception of radio pulses and correlates the angular orientation of the radiated antenna beam or beams in azimuth and/or elevation. Range is determined by measuring the time it takes for the radio wave to go out to the object and then return to the receiving antenna. The direction of a detected object from a radar site is determined by the position of the rotating antenna when the reflected portion of the radio wave is received.
Modern radar is very reliable and there are seldom outages. This is due to reliable maintenance and improved equipment. There are, however, some limitations that may affect ATC services and prevent a controller from issuing advisories concerning aircraft that are not under his or her control and cannot be seen on radar.
The characteristics of radio waves are such that they normally travel in a continuous straight line unless they are “bent” by atmospheric phenomena, such as temperature inversions, reflected or attenuated by dense objects such as heavy clouds and precipitation, or screened by high terrain features. Radar signals degrade over distance, cannot penetrate through solid objects such as mountains, and the fastest radar updates every 4.7 seconds. By contrast, the satellite signals used with Automatic Dependent Surveillance−Broadcast (ADS−B) do not degrade over distance, provide better visibility around mountainous terrain and allows equipped aircraft to update their own position once a second with better accuracy.
ATC Radar Beacon System (ATCRBS)
The ATC radar beacon system (ATCRBS) is often referred to as “secondary surveillance radar.” This system consists of three components and helps in alleviating some of the limitations associated with primary radar. The three components are an interrogator, transponder, and radarscope. The advantages of ATCRBS are the reinforcement of radar targets, rapid target identification, and a unique display of selected codes.
Growing air traffic in the National Airspace System (NAS) will be addressed through the use of ADS-B, which not only provides all the same information the ATCRBS, but will do so more rapidly and with significantly more accuracy. By broadcasting aircraft position information to a ground station, ADS–B can also provide coverage in areas that do not have radar coverage. In addition, ADS–B provides trajectory information that includes speed and direction of motion.
Figure 14-42. Light gun signals.
Transponder
The transponder is the airborne portion of the secondary surveillance radar system and a system with which a pilot should be familiar. The ATCRBS cannot display the secondary information unless an aircraft is equipped with a transponder. A transponder is also required to operate in certain controlled airspace as discussed in Chapter 15, “Airspace.”
A transponder code consists of four numbers from 0 to 7 (4,096 possible codes). There are some standard codes or ATC 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. Figure 14-43 lists some standard transponder phraseology. Additional information concerning transponder operation can be found in the AIM, Chapter 4.
Figure 14-43. Transponder phraseology.
Automatic Dependent Surveillance–Broadcast (ADS-B)
Automatic Dependent Surveillance−Broadcast (ADS−B) is a surveillance technology being deployed throughout the NAS to facilitate improvements needed to increase the capacity and efficiency of the NAS, while maintaining safety. ADS-B supports these improvements by providing a higher update rate and enhanced accuracy of surveillance information over the current radar-based surveillance system. In addition, ADS-B enables the expansion of air traffic control (ATC) surveillance services into areas where none existed previously. The ADS-B ground system also provides Traffic Information Services-Broadcast (TIS-B) and Flight Information Services-Broadcast (FIS-B) for use on appropriately equipped aircraft, enhancing the user’s situational awareness (SA) and improving the overall safety of the NAS.
The ADS−B system is composed of aircraft avionics and a ground infrastructure. Onboard avionics determine the position of the aircraft by using the GPS and transmit its position, along with additional information about the aircraft, to ground stations for use by ATC and nearby ADS-B equipped aircraft.
In the United States, ADS−B equipped aircraft exchange information on one of two frequencies: 978 or 1090 MHz. The 1090 MHz frequency is associated with Mode A, C, and S transponder operations. 1090 MHz transponders with integrated ADS−B functionality extend the transponder message sets with additional ADS−B information. This additional information is known as an “extended squitter” message and referred to as 1090ES. ADS−B equipment operating on 978 MHz is known as the Universal Access Transceiver (UAT).
Radar 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. ATC 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. [Figure 14-44] 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).