This information is intended for recreational radio monitoring use only and is not intended for aviation.

Welcome to my Southern California Aviation Monitoring guide
Aviation Monitoring Guide
Controlled/Uncontrolled airports
Airspace
Automated Terminal Information System ( ATIS)
Clearance
Ground
Tower
TRACON
Air Route Traffic Control Center
Altitude
Say WHAT?
Hooked on phonetics
Call-signs
Sectional Maps
Runways
Frequencies
Navigation
Emergency Locator Transmitter
Airline Company Frequencies

Aviation Monitoring Guide

Welcome to the Freq Of Nature Aviation Monitoring Guide. I'm not a pilot but I play one on the computer. After first playing Flight Sim on the old Apple II, where the runway was a single white vector line on a black and white monitor, I've been hooked on flying digital aircraft. If your interested in Flight Sims then you might want to check out www.flightsim.com. This guide is only intended to cover those aspects of aviation that would be of interest in radio monitoring. If you would like more information on aviation then I suggest you visit a pilot shop at a local general aviation airport where you can purchase books, maps and other aviation material or even learn to fly. I'll try to keep this up to date and add things as time permits. If you have any questions or comment, I love comments, please e-mail them to tracy@freqofnature.com.

Controlled/Uncontrolled airports

Controlled airports are generally larger airports that have enough traffic to justify full time air traffic controllers. Uncontrolled airports have less traffic so a full time air traffic controller is not available. Some medium size airports will have hours of operation in which the airport is controlled. The hours are normally during daylight hours. After the controllers have left for the day the airport may either close or be uncontrolled. When an airport is operational but uncontrolled then there is a UNICOM frequency that the pilots use to talk to each other. Many airports have a published UNICOM frequency but generally airports with a control tower use the UNICOM frequency 122.95MHz and those without a control tower 122.9MHz. UNICOM frequencies are frequently used at air shows for temporary air traffic control by the air show Air Boss. This allows the Air Boss to have his own frequency while the airport controllers keep their tower frequency. Control of the air space can then be handed off between the two controllers without any interruption in radio communications.

Other UNICOM Frequencies used at uncontrolled airports
122.7000	Uncontrolled airports
122.7250	Uncontrolled airports
122.8000	Uncontrolled airports
122.9750	Uncontrolled airports or above 10,000
123.0000	Uncontrolled airports
123.0500	Heliports
123.0750	Uncontrolled airports

Airspace
Airspace is divided into several different classes.
(Click above image for large view)
Class A: Airspace from 18,000-60,000 feet above sea level. Aircraft in Class A airspace normally will be talking with Center controllers. Air traffic control is divided into low altitude sectors (18,000 ft - 23,000 ft) and high altitude sectors (24,000 and above) (See ZLA Center menu item at the top of this page for detailed information on Los Angeles Class A airspace). Class B: Airspace from the surface to 10,000 feet 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 (some Class B airspace areas resemble upside-down wedding cakes), and is designed to contain all published instrument procedures once an aircraft enters the airspace. Clearance from air traffic controllers is required for all aircraft to operate in these areas. Los Angeles (LAX), San Francisco (SFO) and San Diego (SAN) are the only airports in California that are Class B airspace. Class C: Airspace from the surface to 4,000 feet above the airport elevation surrounding those airports that have an operational control tower and are serviced by a radar approach control. These are busy airports that don't qualify for Class B airspace. An example would be Burbank Airport and other airports that have enough traffic to justify Class C airspace. Although the configuration of each Class C airspace area is individually tailored, the airspace usually consists of a 5 NM radius core surface area that extends from the surface up to 4,000 feet above the airport elevation, and a 10 NM radius shelf area that extends from 1,200 feet to 4,000 feet above the airport elevation.

California Airports that are Class C
Beale AFB
Burbank-Glendale-Pasadena
Fresno Air Terminal
Monterey Peninsula
Oakland Metropolitan International
Ontario International
March AFB
Sacramento International
San Jose International
Santa Ana-John Wayne
Santa Barbara Municipal

Class D: Airspace from the surface to 2,500 feet above the airport elevation surrounding those airports that have an operational control tower. The configuration of each Class D airspace area is individually tailored but typically the airspace extends 2,500 feet above the ground and out in a 4nm radius. When instrument procedures are published, the airspace will normally be designed to contain the procedures, however, the airspace is designated Class E. Class E: Airspace is not Class A, Class B, Class C, or Class D, and it is controlled airspace, it is Class E airspace. This includes airspace above 60,000 feet above sea level. Class G: Airspace that is uncontrolled. (Click above image for large view)

Automated Terminal Information System (ATIS)

All journeys have a beginning and for pilots it starts by monitoring ATIS. ATIS is the first frequency of many frequencies a pilot will tune on his journey. ATIS is a prerecorded message that repeats over and over and is updated several times a day. The recording contains information that the pilot needs prior to flight such as the weather, runway information and other notices of importance. Some airports have a phone number you can call to listen to their ATIS reports. Many airports use computer automation to generate ATIS reports from a text script. This produces a more accurate recording since the computer isn't susceptible to dyslexia and isn't prone to putting an extra "ah" or "umm" in with the report. The ATIS report will end with a letter in military phonetics I.E. "You have ALPHA" or "You have ZULU". This is used to insure that the pilot has the current report. If the current report is "CHARLIE" and the pilot tells the controller that he has "ALPHA" then the controller knows the pilot does not have the current report and will ask the pilot to monitor the more recent ATIS report before contacting the controller. Here is the Van Nuys Airport ATIS from September 12th, 2001. Prior to monitoring ATIS the pilot will have filed a flight plan so that air traffic controllers will know his intentions once he's in the air. While filing a flight plan is mandatory for IFR (Instrument Flight Rules) flights and those flights that will transit certain air space like Class C air space, it's optional for VFR (Visual Flight Rules). It's kind of pointless to file a flight plan if all your going to do is perform touch-and-goes at the airport.

Clearance

The Clearance Controller gives out the entire IFR clearance the pilot needs and any modifications to the pilots flight plan before flying.Once the pilot has filed a flight plan and listened to the airports ATIS he is ready to contact the Clearance Controller. This is the second of many frequencies a pilot will use throughout his journey and he has yet to move an inch. The pilot will contact the Clearance Controller with the latest ATIS report the pilot has monitored and the Clearance Controller will give the pilot flight instructions. The pilot will read back the instructions that the clearance controller just read just to make sure the pilot 'copied' the instructions correctly, then the pilot is handed off to the Ground Controller. (This FAA diagram shows the communication processes of a typical flight)

Ground

The Ground Controller is responsible for all movement on the ground at the airport.Once a pilot is ready to taxi to the runway he will contact the Ground Controller to receive instructions on which taxiways to use to arrive safely at the runway. Since Ground Controllers are responsible for all movement on the ground at the airport you will frequently hear them giving instructions to not only aircraft but other vehicles like maintenance and security vehicles. You might hear some pilots unfamiliar with the airport request 'Progressive Taxi Instruction' especially at airports with complex taxiways. Even experienced pilots like the pilots of Air Force One request such baby-step instruction. It's better to be safe than sorry. Once the pilot has safely arrived at the desired runway he will switch to the Tower Controllers frequency without so much as a 'good-day' to the Ground Controller.

Tower

The Tower Controller is responsible for the aircraft in the immediate area around the airport (Up to 3000 feet and 5 miles from the airport).When the pilot arrives at the runway and is ready for take off he will contact the Tower Controller for clearance to depart. There may be a slight delay between the time the pilot arrives at the runway and when he contacts the Tower Controller so that he can perform last minute checks and run the engine up in speed. After the last minute checks and engine run up the pilot will contact the Tower Controller informing him of what runway he's at and request permission to enter the runway for take off. Depending on what aircraft are taking off or in final approach the pilot will eventually be given permission to enter the runway and take off. Other information like the departure frequency and procedures will be given to the pilot. This information should not be new to the pilot since he also heard it from from the Clearance Controller. Many airports in busy airspace have SIDs (Standard Instrument Departure) routes. These departure instructions keep departing aircraft from venturing into unwanted obstacles like jet ways, buildings and mountains. Once the pilot leaves the airports airspace he will be handed off to either a TRACON or ARTCC controller to receive new flight instructions on his journey.

TRACON

TRACON Controllers use radar and non-radar capabilities to provide approach control services to aircraft arriving, departing or transiting airspace controlled by their facility. When an aircraft is in the departure, descent and approach phases of a flight, the aircraft is being monitored by controllers in the TRACON (Terminal Radar Approach Control). TRACONs are facilities that control air traffic in congested areas that typically cover air space around several airports. In the Los Angeles vicinity the TRACON is referred to as 'SOCAL'. Other examples of TRACONs are 'MUGU' which controls the areas around the airports in Ventura County and 'JOSHUA' which controls the areas around Edwards AFB. Some TRACONs provide part-time air traffic control so they will share air traffic control with the CENTER controllers depending on the time of day. One TRACON can handle the air traffic for several different airports in its vicinity. The airspace of a TRACON has various dimensions. Dallas-Ft. Worth TRACON, for example, monitors the air-space from 17,000 feet and below, and approximately a 40 mile radius from the Dallas-Ft. Worth airport. Approach Controller - Directs several lines of descending aircraft into one smooth flowing line of aircraft as their courses take them closer to the destination airport. This line of aircraft is commonly called 'a string of pearls' because from the vantage point of the destination airport the many aircraft landing lights resemble a string of pearls in the sky. Feeder Controller - Takes the hand-off from the Center and directs the arrival aircraft from about 40 miles out into the destination airport. Departure Controller - Routes air traffic immediately upon takeoff via a preferential departure route (PDR) leading away from the departure airport as the aircraft ascends to the en route phase of flight. Once an aircraft leaves the air space of the TRACON, either by altitude or distance, they will be handed off to the ARTCC (Air Route Traffic Control Center).

Air Route Traffic Control Center

The airspace over the United States is divided into 21 large areas called Centers. (Click map for large view) Within each Center are a number of TRACONs. TRACON is an acronym for Terminal Radar Approach CONtrol. Within each TRACON are a number of airport control towers (referred to as satellite airports). Overseeing all of this activity in the Centers and TRACONs is the Air Traffic Control System Command Center. Here "Central Flow Control" looks for situations that will create bottlenecks or other problems in the efficient flow of air traffic, and responds with a management plan to keep the air traffic flowing smoothly. It's kind of like completing a crossword puzzle which changes all the time, oh and you have a time limit. Once an aircraft is in the en route phase of its flight, it is monitored by the region's Air Route Traffic Control Center. Each Center is divided into High and Low altitude sectors. As and aircraft passes through each Center's airspace, it is handed off from Center to Center until it reaches its destination airport and prepares for descent. At this point it is handed off to the TRACON and then handed off to the destination airport's control tower. Behind the scenes are several air traffic controllers with specific duties, some of which do not involve radio communications. Radar Controller - The radar controller is in charge of the sector. This controller maintains positive separation among all aircraft under his/her control. Separation standards from a Center are defined as 5 miles laterally or longitudinally for aircraft flying at the same altitude, or 1,000 feet vertical separation below 29,000 feet and 2,000 feet vertical separation above 29,000 feet. The radar controller is responsible for all air-to-ground communications. Coordination with other sectors and facilities is a duty shared by both the radar controller and the radar associate controller. Radar Associate Controller - The radar associate controller assists the radar controller and receives flight plan information on aircraft anywhere from 5 to 30 minutes in advance of aircraft entering the sector. The associate controller works with the radar controller to plan separation of aircraft and to coordinate with other sectors and facilities. Radar Hand-off - The radar hand-off controller assists the radar team when air traffic becomes very heavy. This controller serves as another set of eyes to maintain separation of aircraft and coordinate with other controllers and facilities as necessary. This extra help also serves to maintain a smooth and efficient flow of air traffic. Five Miles And A Thousand Feet of separation is the job of these air traffic controllers. Listen to one that almost crossed that line. If you really want to get a feel for how this works then I suggest you purchase Microsoft FlightSim 2002 or 2004 which now includes virtual air traffic controllers that are controlling not just your aircraft but other aircraft. Microsoft Flight Simulator uses real world air traffic control data in it's 'game' so when you fly from New York to Los Angeles you will be handed off to the same frequencies that a real world flight would use. If that's not real enough for you, then you can join in with other virtual pilots and air traffic controllers on the Internet. Just keep in mind that you will have to go through virtual flight or air traffic control school before you can do that. As real as it can get with bits, bytes and nibbles. Virtual Los Angeles Center http://www.laartcc.org Virtual Air Traffic Control (Governing body) http://www.vatsim.net Southern California Approach [Source: LowApproach.com] - This is a live feed of SoCal and Pt. Mugu Approach. You can listen to aircraft entering Burbank (BUR), Camarillo (CMA), Oxnard (OXR), Pt. Mugu Naval Air Station (NTD) and Los Angeles International (LAX) airspace from the North/Northwest part of southern California. You will need the RealAudio Player.

Altitude

Altitudes at or above 18,000 feet are rounded to the nearest 100 and are preceded with "Flight Level" so a plane flying at 18,000 feet would be at "Flight Level One Eight Zero" while a plane at 27,500 feet would be at "Flight Level Two Seven Five".Below 18,000 feet the altitude is expressed in thousands and hundreds of feet so a plane flying at 17,500 feet would be flying at "Seventeen Thousand Five Hundred". The reason for the different altitude reporting methods is because above 17,500 feet pilots are supposed to set their altimeter barometer correction to 29.92 standard. This results in inaccurate MSL (Mean Sea Level) altitudes, but it keeps everyone out of each others' way as fast aircraft move through areas of differing barometric pressure. Thus, the term " Flight Level" instead of altitude. In conditions when barometric pressure is unusually low, there is what's known as the lowest usable flight level, to prevent the situation described above. Above 10,000 feet, the correct phraseology is to read off the numbers and then thousand; for example, "One Seven Thousand".

Say WHAT?

A good pilot thinks before he speaks. The first thing you will probably notice if your new to aeronautical radio monitoring is how fast they all talk, like they are reading from a script. There are two reasons they talk so fast. The first reason is that there is a lot of pilots talking to one or two controllers on one or two frequencies. That's a lot of radio traffic and it's almost always constant. The second reason is that they all know what to expect and it's more formality than anything else. When a pilot contacts the Clearance Controller the pilot already knows what the Clearance Controller is going to say in response. It's one big radio ballet.

Hooked on phonetics

If Andy Rooney had done a story on aviation monitoring I imagine his opening line might have been "Have you ever noticed how all pilots sound a like?"The International Civil Aviation Organization (ICAO) phonetic alphabet is used by FAA personnel when communications conditions are such that the information cannot be readily received without their use. ATC facilities may also request pilots to use phonetic letter equivalents when aircraft with similar sounding identifications are receiving communications on the same frequency. Pilots use the phonetic alphabet when identifying their aircraft during initial contact with air traffic control facilities. Additionally, use the phonetic equivalents for single letters and to spell out groups of letters or difficult words during adverse communications conditions. The Queen of England might roll her eyes at this butchery of her English language but it serves it's purpose by maintaining a standard accent that all aviators can, like for sure, understand. This way a pilot from Jamaica can understand and communicate instructions when talking with air traffic controllers in err Boston, California and Ottawa, eh? The pronunciations closely resemble the Queen's English language pronunciations so it's not very noticeable to those new to aviation monitoring, but like a popular song that gets stuck in your head, now that you've read this tutorial on aviation phonics it will be quite evident next time you tune your radio scanner to monitor air traffic on WUN TOO TREE decimal ZEE-RO TOO FIFE.

Phonetic Alphabet/Morse Code

Call-signs

All commercial and private call-signs in the United States start with the letter 'N'.Once the pilot has initiated contact with a controller the pilot will give his full call sign, after that the control may just use the last two or three digits of the call-sign to to save precious air time. This can be confusing and I've heard situations that made my blood run cold when a controller is giving instructions to one pilot and the wrong pilot confirms the instructions. One time it was so bad at a local airport that the pilots started correcting the controller. A controller might use the aircraft type then two or three of the last digits in the call-sign to identify an aircraft. So if it's a Bonanza with a call-sign of N1238 the controller might refer to the aircraft as "Bonanza Thirty Eight". This reduces the chance of confusing two aircraft of different types with similar call signs. Scheduled commercial flights are referred to with their company name and flight number so a United Airlines flight 123 would be "United One Two Three". Not all commercial airliners use their company name to identify themselves I think because some company names are similar like American West and American Airlines so they use a different name like Cactus so an American West flight 349 would be "CACTUS Three Four Niner" while and American Airline flight 349 would be "AMERICAN Three Four Niner". Military aircraft also use colorful call-signs like Air force One and Viper Three etc. Since I'm fairly new to military air monitoring I'll add new information as I go. Note of interest: It's rumored that Air force One used to use it's tail number for it's call sign like all non-scheduled flights but an air traffic controller got it confused with another aircraft so to reduce the chance for confusion in the future they started referring to the presidential aircraft as Air force One. If the President is on a Marine aircraft then it's referred to as Marine One and if it's a private aircraft the call sign is Executive One. If you would like to know what kind of aircraft and even who the owner is, there is a database at www.Landings.com. Check out their home page also for more interesting information and databases.

Sectional Maps

To make your aeronautical radio monitoring most enjoyable you should visit a pilot shop near your local airport and purchase the sectional chart for your area. Jeppesen, a private company, produces high quality maps that cost about $7.00 and it is well worth the money. In addition you can purchase terminal area charts which are at about double the scale of a sectional chart but covers less area. (Click above image for large view) There are also high and low altitude maps that cover large areas with less detail which are great for understanding the flight paths of aircraft that are controlled by the different center. Detailed maps of airports and their approach and departure procedures are also available at your local pilot shop as well as online at www.myairplane.com.

Runways

Have you ever wondered how they come up with the numbers for runways? Imagine the runway is the needle of a compass. If the runway were pointing at 90 degrees of magnetic north then the runway would be runway 9 and the other end of the runway would be runway 27 (270 degrees, the last digit is dropped). If runways parallel each other then they are called runway left and runway right so you might have runway 9L/27R and runway 9R/27L. Even though runways don't always exactly line up to these rounded off degrees they are rounded off to the nearest. So runway 27 might actually be 273 degrees. Close enough for government work but don't despair, the actual degree of the runway is listed on the approach plates used by pilots.Taxiways are normally assigned letters of the alphabet and are in order from A to Z. Some larger airports might have more than 26 taxiways so they will assign them numbers at the end (Taxiway H1 and H2). Each airport's taxiway scheme is different (some more unusual than others) so you will want to visit Jeppesen's Online Publications for a database of airport diagrams. (Click above image for large view)

Frequencies

The general aviation air band is between 108MHz and 136.975MHz.The frequencies between 108MHz and 117.975MHz are used for navigational radios so there is not much there to monitor unless you get your kicks from reading Morse Code. Some of these navigational aid frequencies double as FSS (Flight Service Station) frequencies so you might hear the occasional conversation between FSS and a pilot. If that is the case then point your browser to www.AirNav.com where you will find a database of navigational radio sites along with their Call Letters. The Military or UHF air band is between 225MHz and 400MHz. You will find many ATCs broadcasting to both the VHF and UHF bands so if you don't have the UHF frequency plugged in then you might only hear the controllers side of the conversation.

Navigation

The frequencies between 108MHz and 117.975MHzare mostly navigational aids.Some stations will broadcast their call signs in mores code or broadcast weather information on the same frequency that is being used for navigation but that's about it. There are basically two kinds of navigational systems, VOR (VHF Omni directional Range) sometimes called VORTAC (VHF Omni directional Range Tactical Air Navigation) and NDB (Non Directional Beacon). Either of these navigation aids might have a DME (Distance Measuring Equipment). A NDB is simply a radio broadcast that the equipment inside the aircraft picks up and displays a needle pointing in the direction of the transmission relative to the aircrafts heading. NDBs transmit in the Military Air Band while VORs transmit in the Civilian Air Band between 108MHz and 117.975MHz. A VOR is a little more complicated and much much more valuable during instrument navigation. A VOR has several radials (I don't know anything about the technical workings of the equipment) that allows the aircraft to tell not just what direction the transmission is relative to the aircraft but also what radial the aircraft is on. You can pin point your exact location by tuning in to two VORs and drawing a line out from each radial until they intersect .. presto you know where you are. These navigational aids also compute the distance to the station as well as air speed. If you would like to try a VOR simulation online then check out this URL http://www.relia.net/~george/aviation/sim How does it work? Marc Toh was kind enough to provide the following explanation of how these navigational aids work. VOR is VOR, VORTAC is a VOR with a TACAN co-located. TACAN is used by the military, but civilian aircraft can get distance information from the TACAN. VORTACs always have DME, whereas VORs may or may not have DME. NDBs transmit on the frequency range just below AM radio. ADFs, the instrument in the aircraft to tune in the NDBs, have the ability to tune in AM stations. Helps in reliving the boredom of a long flight. The VOR works by sending out 2 signals, a reference and a phase, and the airborne receiver compares the time difference between receiving the signals to determine the radial it is on. The most common analogy used is the lighthouse. Assume the light takes 360 seconds to make one complete sweep. At 0 seconds the light begins it's rotation from north, at the same time a reference light goes off to indicate 0 seconds. Someone due east will see the reference light go off. 90 seconds later, he will see the rotating light sweep by. Someone due west will see the light sweep by 270 seconds after seeing the reference light. Of course, VORs work at a much faster rate than that.

Emergency Locator Transmitter (ELT)

ELT's of various types have been developed as a means of locating downed aircraft and are required for most General Aviation airplanes. These electronic, battery operated transmitters emit a distinctive downward swept audio tone on 121.5 MHz and 243.0 MHz. If "armed" and when subject to crash generated forces they are designed to automatically activate and continuously emit these signals. The transmitters will operate continuously for at least 48 hours over a wide temperature range. A properly installed and maintained ELT can expedite search and rescue operations and save lives. Aircraft Emergency Location Transmitter (ELT) WAV file on 121.5 AM

Special thanks to Marc Toh for contributing information.

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