{ light aircraft radio design evolves, provides for progressive expansion of your equipment as your training and operational needs increase. For example, if you depart under IFR from an uncontrolled airport and proceed via Victor airway to another uncontrolled airport, your communication/navigation needs may be as little as one VOR frequency and one transmitting frequency for communication with FSS.

When you progress to all-weather IFR flying in and out of unfamiliar terminal areas, your workload can be excessive unless you have sufficient standby equipment for frequent changes of communications channels. Figure 172 shows how communications equipment can be grouped for quick reference and operation with minimum distraction from the problem of aircraft control.

Radiotelephone Procedure

From the time you contact ground control for taxi instructions the effectiveness of your coordination with Air Traffic Control will depend upon your competence in communications and your knowledge of traffic procedures under Instrument Flight Rules. Many students have no serious difficulty in learning basic aircraft control and radio navigation, but stumble through even the simplest radio communications. During the initial phase of training in Air Traffic Control procedures and radiotelephone techniques, some students experience difficulty.

Why should talking and listening to a controller pose any problems? The average person takes his speaking and listening habits for granted and has had no occasion to develop specialized skills associated with radio communications. Studies of listening comprehension show that most people listen with low efficiency, even when consciously attempting to remember what they hear. The poor listener is easily distracted. From habit he tolerates conditions unfavorable to concentration. His mind wanders when he hears anything unexpected or difficult to understand. He is inclined to be more concerned with what he is about to say than with what he should be listening to. When in a confusing situation he is more easily aroused emotionally, and may have trouble comprehending

what he hears.

These deficiencies are intensified for the pilot in a busy air traffic environment. In addition to attending to cockpit duties demanding rapid division of attention, quick judgment, concentration, and careful planning, you the pilot must be continuously alert to communications from Air Traffic Control. You should be prepared to listen and to transmit in the brief and unmistakably clear terms vital to orderly control.

You attain proficiency in radiotelephone technique just as you do in developing any other skill. You should first recognize that radio communications under Instrument Flight Rules, though not difficult, require speaking and listening habits different from those you have been accustomed to. Skill in transmitting and listening will come rapidly once you have studied and practiced the basic terminology.

The FAA controller is intensively trained to speak clearly and concisely in an abbreviated terminology understandable to airmen, but somewhat unintelligible to others. He uses standard words and phrases to save time, reduce radio congestion, and lessen the chances of misunderstanding and confusion. However, the most competent controller won't "get through" to you under the best conditions unless you are ready to listen and understand.

Communication is a two-way effort, and the controller expects you to work toward the same level of competency that he strives to achieve. Tape recordings comparing transmissions by professional pilots and inexperienced or inadequately trained general aviation pilots illustrate the need for effective radiotelephone technique. In a typical instance, an airline pilot reported his position in 5 seconds; whereas a private pilot reporting the same fix took 4 minutes to transmit essentially the same information. The difference lay, not in equipment and flight experience, but in communication technique. The novice forgot to tune his radio properly before transmitting, interrupted other transmissions, repeated unnecessary data, forgot other essential information, requested instructions repeatedly, and created the general impression of cockpit disorganization. As encouragement to the novice who is embarrassed and concerned about broadcasting his inexperience, let him remember that every pilot had to make a beginning and was not expected at first to communicate like a veteran airline pilot. But the private pilot who learns and practices standardized words and phrases until they become part of his normal radio vocabulary will be able to communicate effectively even under adverse reception conditions.

Phonetic Alphabet

It is often necessary in transmitting to identify certain letters and/or groups of letters, or to spell out difficult words, since certain sounds have low intelligibility when mixed with a background of other noises. The standard phonetic alphabet (Fig. 173) identifies each letter of the alphabet with a word that is easily understood. These words are pronounced to make the message clear when individual letters are trans

Numbers are usually of extreme importance in radio messages and are difficult to hear among other noises. The standard pronunciations in Figure 173 have been adopted because they have been found most intelligible.

a. Normally, numbers are transmitted by speaking each number separately. For example, 3284 is spoken as "tree too ait fo-wer."

b. There are certain exceptions to the above rule. Figures indicating hundreds and thousands in round numbers, up to and including 9,000 are spoken in hundreds or thousands as appropriate. 500 is spoken as "fife hundred"; 1,200 as "wun thousand too hundred." Beginning with 10,000, the individual digits in thousands of feet are spoken. For 13,000, say "wun tree thousand", for 14,500, say "wun-fo-wer thousand fife hundred."

c. Aircraft identification numbers are spoken as individual digits/letters. 1234Q is spoken as "wun too tree fo-wer Keh-beck."

d. Time is stated in four digits according to the 24-hour clock. The first two digits indicate the hour; the last two, minutes after the hour (Fig. 174), as in "wun niner too zero"; "zero niner fo-wer fife."

e. Field elevations are transmitted with each number spoken separately, as in Figure 174.

Procedural Words and Phrases

The words and phrases in Figure 175 should be studied and practiced until they are readily and easily used and clearly enunciated. To pilots and controllers, their meanings are very specific. Careless or incorrect use can cause both delay and confusion.

Voice Control

Students inexperienced in the use of the microphone are usually surprised at the qualit of their own transmissions when they are taped and played back. Words quite clear when spoken directly to another person can be almost unintelligible over the radio. Effective radiotelephone technique sounds self-conscious and unnatural when you practice it, both because the terminology is new and because you are habitually more concerned with what you are saying than in how it sounds. Maximum readable radiotelephone transmissions depend on the following factors:

1. Volume.-Clarity increases with volume up to a level just short of shouting. Speaking loudly, without extreme effort or noticeably straining the voice, results in maximum intelligibility. To be understood, the spoken sound must be louder at the face of the microphone than the surrounding noises. Open the mouth so the tone will carry to the microphone. A higher-pitched tone is easier to hear than a lower one. A distinct and easily readable side tone in your earphones or speaker is a reliable index of correct volume.

2. Tempo.-Effective rate of speech varies with the speaker, the nature of the message, and conditions of transmission and reception. Note the following suggestions for improving your rate of transmission:

a. Talk slowly enough so that each word and phrase is spoken distinctly, particularly key words and phrases.

b. Talk slowly enough so the listener will have time, not only to hear, but to absorb the meaning.

3. Pronunciation and Phrasing.-As you notice the differences in the transmission of various pilots and controllers, you can readily identify those with exceptional skill. They sound nat ural and unhurried. The words are grouped for easy readability. They pronounce every word clearly and distinctly without apparent effort, without unnecessary words, and without "uh's" and "ah's." They create the impression of compe tence that any expert conveys after enough study and practice.

Practice

Many excellent audio training aids are available for practicing radiotelephone procedures. With tapes or records, a microphone, and writing materials, you can develop communications skills under excellent simulated conditions. Practice until you can transmit concisely, hear accurately, and listen critically. Hearing is largely a matter of having an adequate receiver and knowing how to tune it. Critical listening is a more compli

Out

Over

Read back

Roger

Say again Speak slower

Stand by

That is correct
Verify
Words twice

Meanings

Yes.

Proceed with your message.

Self explanatory.

Self explanatory.

That is not correct.

Self explanatory.

Self explanatory.

Self explanatory.

Check with the originator.

cated skill. You are ready to listen to a controller when you are thoroughly familiar with your communications equipment and are ready to copy his transmission, evaluate what he says, and if necessary read it back to him without neglecting any other cockpit duties that may demand your attention. Study of Air Traffic Control procedures under Instrument Flight Rules will enable you to "keep ahead" of communications-just as you keep ahead of your basic flying and navigation-by knowing what is ahead of you and attending to details in the proper sequence at the appropriate time.

Reminders on Use of Equipment

1. Maintain a "readiness" to communicate. With your flight log handy, charts in order, and other necessary materials readily available, you can eliminate fumbling and confusion. You can

not organize an intelligible message, or listen to one, in a disorganized cockpit.

2. Know your radiotelephone equipment and practice tuning it. Check the knobs, switches and selectors before you transmit. Monitor the frequency you are using before transmitting. If you hear nothing on a normally busy terminal frequency, for example, check your volume control; you may be interrupting another transmission.

3. Check your clock before transmitting to Flight Service. Other pilots are listening to scheduled weather broadcasts beginning at 15 minutes past the hour.

4. Never subordinate aircraft control to communications. Don't turn your aircraft loose in your haste to transmit.

5. Learn to take notes as you listen. Make written notes of times, altitudes, and other information as you hear it. You have enough to think about in planning ahead without having to waste time thinking back.

System Details

Up to this point, your instrument training has been concerned largely with problems within the cockpit. While you have been acquiring proficiency in the use of basic flight instruments and NAV/COM equipment, your instructor has kept a watchful eye on other traffic. He has told you what maneuvers to execute, what radials to fly, when and where to go. Instrument flying would be relatively simple if your instrument training. ended with mastery of these basic techniques and with a safety pilot aboard to keep you headed in the right direction, safely separated from other traffic. Your problem now is to learn how to use the facilities, services, and procedures established by the Air Traffic System to provide directional guidance, terrain clearance, and safe

separation for aircraft operating under Instru ment Flight Rules. The extent of this system and the facilities maintained for airspace users can be appreciated by visualizing the tremendous expansion of aviation since 1903 when only one airplane used the national airspace.

Figure 176 shows the low-frequency radio facil ities serving the Los Angeles-Oakland area in 1934. The navaids provided only one route between those two terminals via the Los Angeles, Fresno, and Oakland range legs.

In 1964, 30 years later, the system in this area included the VOR facilities and routes shown in Figure 177 as well as instrument approach aids. radar coverage, and numerous other facilities and services.

By the 1960's, the Nation's air fleet approached 150,000 aircraft, with as many as 70,000 people

loft at any busy hour, most of them converging on, or departing from, major metropolitan areas. In 1969, the 2,110 navigation aids needed to keep these aircraft moving safely throughout the 50 States were listed as follows (exclusive of nondirectional homing beacons, standard broadcasting stations, precision approach radar systems, and non-Federal or special use aids):

27 Air Route Traffic Control Centers (includes 2 Center/RAPCONS and 1 Center/Tower).

90 Air Route Surveillance Radar (ARSR). 155 Airport Surveillance Radar (ASR) - (includes 36 military radars which provide service for civil airports).

952 VOR/VORTACS-(includes 27 non-Federal and 42 military which have been incorporated into the "Common System").

279 Instrument Landing Systems (ILS).

256 Approach Light Systems with Sequence Flashers (ALS).

351 Towers and Combined Station/Towers (CS/Tincludes 30 non-Federal).

The airways system resembles its automotive counterpart in many ways. Whether you travel by Federal airway or Federal highway, the system must provide a controlling agency, procedural rules, directional guidance, highways between population centers, and a means of access between highways and terminals. The components of the Air Traffic System, the controlling agency, and the procedures established for your use of the system are discussed in this and the following chapter. In a later chapter, you will apply what you have learned to a sample flight planning problem.

The Federal airways network is based upon the electronic aids already discussed. The navigation system has three component parts: the pilot, the airborne receiver, and the ground navigation facility. When the recognized errors which each contributes are considered, a total system accuracy can be determined. When this accuracy is applied, the area in which obstruction clearance should be provided becomes apparent. Inherent in this concept is the premise that the pilot fly, as closely as possible, the prescribed courses and altitudes.

Obstruction clearance criteria are based on the airborne receiver contributing not more than ±4.2° error to the total system error. Pilot performance must assure a tracking accuracy within ±2.5° (quarter scale) needle deflection. Where these standards are not assured by the pilot, the safety and accuracy normally provided by the criteria are impaired. The VOR and VORTAC facilities are the foundation of the system (Fig. 178). Connecting these facilities is the network of routes forming the Victor Airway System.

Each Federal Airway is based on a centerline that extends from one navigation aid or intersection to another navigation aid (or through several navigation aids or intersections) specified for that airway. The infinite number of radials transmitted by the VOR permits 360 possible separate airway courses to or from the facility, one for each degree of azimuth. Thus, a given VOR located within approvimately 100 miles of several other VORS may be used to establish