Radio Communications

When most people hear pilots or air traffic controllers speak on the radio, they think they're hearing another language!  In this edition of Spotting 101, we will dispel that myth, and show you how easy it is to follow what they are saying, what they intend to do, and how they do it in as little time as is required.

Basics

The first thing you will need is a VHF communications receiver to listen in on the action.  These are more commonly known as scanners.  They are available from electronic supply shops for anywhere from $75-$100, and can go much higher.  Many scanners have different bands that they can pick up.  A band is a range of frequencies that are all grouped together for specific purposes.  The main requirement is that your scanner be able to pick up the "aircraft band", that is 108.0 MHZ to 136.975 MHZ.  There are two types of signals used in aviation, communication and navigation.

Type	From	To
Navigation	108.000 MHZ	117.950 MHZ
Communications	118.000 MHZ	136.975 MHZ

The range we will be concerned with is the communications range, as this is where pilots and air traffic control speak back and forth.  The navigation range is used for VHF radio navigation.  You can pick up signals from VOR's on your scanner with no problem, however, those signals are usually directed toward the sky, and are difficult to pick up near the ground.  If you do tune one in, you can expect to hear the morse code identifier of that VOR, and possibly a voice-over on top of that, broadcasting some type of weather information, such as HIWAS (hazardous inflight weather advisory service).  The VOR at KIAH is an example of this.  You have to be fairly close, but if you are nearby, tune in 116.6 on your scanner and you will pick this up.

Once you have a scanner that can pick up the aircraft band, its time to start listening in.  The first thing you'll need is frequencies.  Airnav.com has all of the frequencies, plus a lot more information, of each airport in the US.  HoustonSpotters has compiled a list of the most commonly used frequencies in the Houston area, on the Frequency guide page.  There are also links to airport diagrams, if the FAA has provided them.

When you are on the ground, it is not uncommon to only hear one side of the conversation.  You may hear a transmission, then nothing for about 5 seconds.  This is due to the fact that you are just too far away from the other transmitting station (either tower or plane), and the 5 seconds of silence is the other side responding to the transmission you just heard.  There are some areas where you can hear both sides, but you usually get good reception on one side, or poor on both, but very seldom get good reception on both sides of the conversation, without a large antenna to boost the signal, or a high vantage point, close to the airport.

Once you have all of the frequencies you want to listen to, program them into your scanner.  The scanner will loop through each frequency very quickly until it finds activity on a particular frequency, when it does, it will stop and let you listen to it.

Now that we are prepared for listening in, lets talk about what they are actually saying.

There are different people that a pilot will talk to, and knowing which person the pilot is talking to will make it easier to understand, and even anticipate, what the pilot will say next!

Every transmission made in aviation follows a simple flow of four steps.  The words pilots use, and the order in which they use them is all standardized.  This helps to reduce errors and people on both sides of the conversation know what the other is trying to say. Even if they don't receive the entire transmission because of radio noise, they would still get the main intention of the  transmission.  Of course if they just plain don't understand what was said, there are 3 magic words that can save you: "Say again please".

The flow is as follows:

Who to	(Who you are calling)
Who from	(Who you are)
Where	(Your location)
What	(Your request and additional information)

Each transmission will follow this flow.  Some may vary slightly but in general, every transmission will have this information, in this order.  When ATC issues a command to a pilot, they are usually required to read back the information to verify that the intention was clear as to what ATC wants the pilot to do.

There are some basic rules for speaking on the radio:

• Speak clearly and concisely, and as quickly a possible, but take the time you need to get your message across.

• When spelling out letters, use the phonetic alphabet (see below)

• When saying frequencies or headings, or altitudes, always say out each number individually (see the examples below)

Phonetic Alphabet

Each letter in the alphabet has a phonetic word associated with it.  These words are meant to be spoken in lieu of saying a, b, c, etc.  This is to reduce the chance that your transmission is not recieved correctly.  For example, if you speak the following letters:

B, C, D, E, G, P, Z

They all have the same phonetic sound to them, and if you're transmitting this on the radio, it could get very confusing.  However, if you say this:

Bravo, Charlie, Delta, Echo, Golf, Papa, Zulu

Then the chance of miscommunication is greatly reduced, and none of those words sound alike, unlike saying only the letters above.

Lets look at some examples of each category of tranmission, and what they might sound like:

Remember, all letters use the phonetic alphabet, and all numbers are spoken out individually.

For example:

ATIS

ATIS is a listen only transmission.  ATIS codes are given a letter from the phonetic alphabet for each time they are updated.  They are usually updated once per hour, near 50 minutes past, unless severe weather requires an update before then.

ATIS:

"Hobby airport information sierra, two two five zero Zulu weather, wind one five zero at eight, visibility one zero, sky condition, few clouds at three thousand, temperature two eight, dew point two six, altimeter two niner niner eight."

Ground

Pilot:	"Hooks Ground Cessna November one two three four, at the T hangars, request taxi, north departure with Sierra"
Ground Control:	"Cessna November one two three four, Hooks ground, taxi to runway one seven right, via taxiway Kilo, Charlie."
Pilot:	"Taxi to runway one seven right, via taxiway Kilo, Charlie, Cessna November one two three four"

Clearance Delivery

Pilot:	"Sugar land clearance delivery, Cessna November one two three four, IFR to San Antonio."
Clearance Delivery:	"Cessna November one two three four cleared to San Antonio airport as filed, climb and maintain two thousand, expect six thousand one zero minutes after departure, departure frequency is one one Niner point seven."
Pilot:	"Cleared to San Antonio airport as filed, climb and maintain two thousand, expect six thousand one zero minutes after departure, departure frequency is one one niner point seven."
Clearance Delivery:	"Cessna November one two three four, read back correct, contact ground on one two one point four."

Tower

Pilot:	"Hobby tower, Cessna November one two three four ready for departure, one seven right at golf intersection"
Tower:	"Cessna November one two three four, Hobby tower, cleared for takeoff, one seven right at golf"
Pilot:	"Cleared for takeoff, one seven right at golf, Cessna November one two three four"

Approach

Pilot:	"Houston approach, Continental two two five three, with you, six thousand, heading two seven zero"
Approach:	"Continental two two five three, Houston approach, radar contact, descend and maintain three thousand, turn left heading two four zero."
Pilot:	"Descend and maintain three thousand, turn left heading two four zero, Continental two two five three"

Departure

Pilot:	"Houston departure, Jetlink two one eight five with you, one thousand five hundred for four thousand"
Departure:	JetLink two one eight five, Houston departure, roger, climb and maintain one zero thousand, turn left heading zero one zero, proceed on course."
Pilot:	"Climb and maintain one zero thousand, turn left heading zero one zero, Jetlink two one eight five"

Center

Pilot:	"Houston center, Continental three five heavy with you, flight level three five zero, heading two three zero"
Ground Control:	"Continental three five heavy, Houston center, roger, contact Houston approach on one three four point zero"
Pilot:	"Going to one three four point zero, Continental three five heavy."

For a more in depth discussion of radio communications, visit the FAA's AIM chapter on Radio Communications Phraseology and Techniques