15-1

Navigation

Chapter 15

Introduction

This chapter provides an introduction to cross-country 

flying under visual flight rules (VFR). It contains practical 

information for planning and executing cross-country flights 

for the beginning pilot.

Air navigation is the process of piloting an aircraft from 

one geographic position to another while monitoring one’s 

position as the flight progresses. It introduces the need for 

planning, which includes plotting the course on an aeronautical 

chart, selecting checkpoints, measuring distances, obtaining 

pertinent weather information, and computing flight time, 

headings, and fuel requirements. The methods used in this 

chapter include pilotage—navigating by reference to visible 

landmarks, dead reckoning—computations of direction and 

distance from a known position, and radio navigation—by 

use of radio aids.
15-2

Figure 15-1. Sectional chart and legend.

Aeronautical Charts

An aeronautical chart is the road map for a pilot flying under 

VFR. The chart provides information which allows pilots 

to track their position and provides available information 

which enhances safety. The three aeronautical charts used 

by VFR pilots are:

• Sectional 

• VFR Terminal Area 

• World Aeronautical 

A free catalog listing aeronautical charts and related 

publications including prices and instructions for ordering 

is available at the National Aeronautical Charting Group 

(NACG) web site: www.naco.faa.gov.

Sectional Charts

Sectional charts are the most common charts used by pilots 

today. The charts have a scale of 1:500,000 (1 inch = 6.86 

nautical miles (NM) or approximately 8 statute miles (SM)) 

which allows for more detailed information to be included 

on the chart.

The charts provide an abundance of information, including 

airport data, navigational aids, airspace, and topography. 

Figure 15-1 is an excerpt from the legend of a sectional 

chart. By referring to the chart legend, a pilot can interpret 

most of the information on the chart. A pilot should also 

check the chart for other legend information, which includes 

air traffic control (ATC) frequencies and information on 

airspace. These charts are revised semiannually except for 

some areas outside the conterminous United States where 

they are revised annually.

VFR Terminal Area Charts

VFR terminal area charts are helpful when flying in or near 

Class B airspace. They have a scale of 1:250,000 (1 inch 

= 3.43 NM or approximately 4 SM). These charts provide 

a more detailed display of topographical information and 

are revised semiannually, except for several Alaskan and 

Caribbean charts. [Figure 15-2]

World Aeronautical Charts

World aeronautical charts are designed to provide a standard 

series of aeronautical charts, covering land areas of the 
15-3

Figure 15-2. VFR terminal area chart and legend.

world, at a size and scale convenient for navigation by 

moderate speed aircraft. They are produced at a scale of 

1:1,000,000 (1 inch = 13.7 NM or approximately 16 SM). 

These charts are similar to sectional charts and the symbols 

are the same except there is less detail due to the smaller 

scale. [Figure 15-3]

These charts are revised annually except several Alaskan 

charts and the Mexican/Caribbean charts which are revised 

every 2 years.

Lattitude and Longitude (Meridians and 

Parallels)

The equator is an imaginary circle equidistant from the poles 

of the Earth. Circles parallel to the equator (lines running east 

and west) are parallels of latitude. They are used to measure 

degrees of latitude north (N) or south (S) of the equator. The 

angular distance from the equator to the pole is one-fourth 

of a circle or 90°. The 48 conterminous states of the United 

States are located between 25° and 49° N latitude. The arrows 

in Figure 15-4 labeled “Latitude” point to lines of latitude.

Meridians of longitude are drawn from the North Pole to the 

South Pole and are at right angles to the Equator. The “Prime 

Meridian” which passes through Greenwich, England, is 

used as the zero line from which measurements are made in 

degrees east (E) and west (W) to 180°. The 48 conterminous 

states of the United States are between 67° and 125° W 

longitude. The arrows in Figure 15-4 labeled “Longitude” 

point to lines of longitude.

Any specific geographical point can be located by reference 

to its longitude and latitude. Washington, D.C., for example, 

is approximately 39° N latitude, 77° W longitude. Chicago 

is approximately 42° N latitude, 88° W longitude.

Time Zones

The meridians are also useful for designating time zones. A 

day is defined as the time required for the Earth to make one 

complete rotation of 360°. Since the day is divided into 24 

hours, the Earth revolves at the rate of 15° an hour. Noon is 

the time when the sun is directly above a meridian; to the west 

of that meridian is morning, to the east is afternoon. 
15-4

Figure 15-4. Meridians and parallels—the basis of measuring time, 

distance, and direction.

Longitude

L

atitu

d

e

Equator

75°N

60°N

45°N

30°N

15°N

15°S

30°S

45°S

60°S

90°N

75°N

60°N

45°N

30°N

15°N

15°S

30°S

45°S

60°S

90°N

150°W

135°W

120

W°

105 W°

90 W°

75°W

60°W

45°W

30°W

15°W

Prime

m

eridian

150°W

135°W

120

W°

105 W°

90 W°

75°W

60°W

45°W

30°W

15°W

Prime

m

eridian

Figure 15-3. World aeronautical chart.

The standard practice is to establish a time zone for each 

15° of longitude. This makes a difference of exactly 1 hour 

between each zone. In the United States, there are four time 

zones. The time zones are Eastern (75°), Central (90°), 

Mountain (105°), and Pacific (120°). The dividing lines are 

somewhat irregular because communities near the boundaries 

often find it more convenient to use time designations of 

neighboring communities or trade centers.

Figure 15-5 shows the time zones in the United States. 

When the sun is directly above the 90th meridian, it is noon 

Central Standard Time. At the same time, it is 1 p.m. Eastern 

Standard Time, 11 a.m. Mountain Standard Time, and 10 

a.m. Pacific Standard Time. When Daylight Saving Time is 

in effect, generally between the second Sunday in March and 

the first Sunday in November, the sun is directly above the 

75th meridian at noon, Central Daylight Time.
15-5

Figure 15-5. Time zones.

105°

120°

90°

75°

Pacific Standard Time Mountain Standard Time Central Standard Time Eastern Standard Time

These time zone differences must be taken into account 

during long flights eastward—especially if the flight must 

be completed before dark. Remember, an hour is lost when 

flying eastward from one time zone to another, or perhaps 

even when flying from the western edge to the eastern edge 

of the same time zone. Determine the time of sunset at the 

destination by consulting the flight service stations (AFSS/

FSS) or National Weather Service (NWS) and take this into 

account when planning an eastbound flight.

In most aviation operations, time is expressed in terms of 

the 24-hour clock. ATC instructions, weather reports and 

broadcasts, and estimated times of arrival are all based on 

this system. For example: 9 a.m. is expressed as 0900, 1 p.m. 

is 1300, and 10 p.m. is 2200.

Because a pilot may cross several time zones during a flight, a 

standard time system has been adopted. It is called Universal 

Coordinated Time (UTC) and is often referred to as Zulu 

time. UTC is the time at the 0° line of longitude which passes 

through Greenwich, England. All of the time zones around 

the world are based on this reference. To convert to this time, 

a pilot should do the following:

Eastern Standard Time..........Add 5 hours

Central Standard Time..........Add 6 hours

Mountain Standard Time...... Add 7 hours

Pacific Standard Time.......... Add 8 hours

For Daylight Saving Time, 1 hour should be subtracted from 

the calculated times.

Measurement of Direction

By using the meridians, direction from one point to another 

can be measured in degrees, in a clockwise direction from 

true north. To indicate a course to be followed in flight, draw a 

line on the chart from the point of departure to the destination 

and measure the angle which this line forms with a meridian. 

Direction is expressed in degrees, as shown by the compass 

rose in Figure 15-6.
15-6

Figure 15-7. Courses are determined by reference to meridians on 

aeronautical charts.

Course A to B 065°

B

A Course B to A 245°

065°

245°

Figure 15-8. Magnetic meridians are in red while the lines of 

longitude and latitude are in blue. From these lines of variation 

(magnetic meridians), one can determine the effect of local magnetic 

variations on a magnetic compass.

MN

TN

Figure 15-6. Compass rose.

36

33

30

27

24

21

18

15

12

15

6

3

NNW

NNE

NE

N

ESE

SS

WSS

E

WSW

WNW

N

NE

E

SE

S

SW

W

NW

Because meridians converge toward the poles, course 

measurement should be taken at a meridian near the midpoint 

of the course rather than at the point of departure. The course 

measured on the chart is known as the true course (TC). This 

is the direction measured by reference to a meridian or true 

north. It is the direction of intended flight as measured in 

degrees clockwise from true north. 

As shown in Figure 15-7, the direction from A to B would 

be a true course of 065°, whereas the return trip (called the 

reciprocal) would be a true course of 245°.

The true heading (TH) is the direction in which the nose of 

the aircraft points during a flight when measured in degrees 

clockwise from true north. Usually, it is necessary to head 

the aircraft in a direction slightly different from the true 

course to offset the effect of wind. Consequently, numerical 

value of the true heading may not correspond with that of 

the true course. This is discussed more fully in subsequent 

sections in this chapter. For the purpose of this discussion, 

assume a no-wind condition exists under which heading and 

course would coincide. Thus, for a true course of 065°, the 

true heading would be 065°. To use the compass accurately, 

however, corrections must be made for magnetic variation 

and compass deviation.

Variation

Variation is the angle between true north and magnetic north. 

It is expressed as east variation or west variation depending 

upon whether magnetic north (MN) is to the east or west of 

true north (TN).

The north magnetic pole is located close to 71° N latitude, 96° 

W longitude and is about 1,300 miles from the geographic 

or true north pole, as indicated in Figure 15-8. If the Earth 

were uniformly magnetized, the compass needle would point 

toward the magnetic pole, in which case the variation between 

true north (as shown by the geographical meridians) and 

magnetic north (as shown by the magnetic meridians) could 

be measured at any intersection of the meridians.

Actually, the Earth is not uniformly magnetized. In the United 

States, the needle usually points in the general direction of 

the magnetic pole, but it may vary in certain geographical 

localities by many degrees. Consequently, the exact amount 

of variation at thousands of selected locations in the United 

States has been carefully determined. The amount and the 
15-7

Figure 15-9. Note the agonic line where magnetic variation is 

zero.

Easterly Variation Westerly Variation

Agonic Line

Figure 15-10. Effect of variation on the compass.

Zero

variation

N 33 30

W 24 21

S 15 12

E

6 3

N 33 30

W 24 21

S 15 12

E

6 3

N 33 30

W 24 21

S 15 12

E

6 3

West

variation

Eest

variation

NP

MP

SP SP

NP

MP

NP

MP

SP

direction of variation, which change slightly from time 

to time, are shown on most aeronautical charts as broken 

magenta lines, called isogonic lines, which connect points 

of equal magnetic variation. (The line connecting points at 

which there is no variation between true north and magnetic 

north is the agonic line.) An isogonic chart is shown in 

Figure 15-9. Minor bends and turns in the isogonic and agonic 

lines are caused by unusual geological conditions affecting 

magnetic forces in these areas.

On the west coast of the United States, the compass needle 

points to the east of true north; on the east coast, the compass 

needle points to the west of true north.

Zero degree variation exists on the agonic line, where 

magnetic north and true north coincide. This line runs roughly 

west of the Great Lakes, south through Wisconsin, Illinois, 

western Tennessee, and along the border of Mississippi and 

Alabama. [Compare Figures 15-9 and 15-10.] 

Because courses are measured in reference to geographical 

meridians which point toward true north, and these courses are 

maintained by reference to the compass which points along a 

magnetic meridian in the general direction of magnetic north, 

the true direction must be converted into magnetic direction 

for the purpose of flight. This conversion is made by adding 

or subtracting the variation which is indicated by the nearest 

isogonic line on the chart. 

For example, a line drawn between two points on a chart 

is called a true course as it is measured from true north. 

However, flying this course off the magnetic compass would 

not provide an accurate course between the two points due to 

three elements that must be considered. The first is magnetic 

variation, the second is compass deviation, and the third is 

wind correction. All three must be considered for accurate 

navigation.

Magnetic Variation

As mentioned in the paragraph discussing variation, the 

appropriate variation for the geographical location of 

the flight must be considered and added or subtracted as 

appropriate. If flying across an area where the variation 

changes, then the values must be applied along the route of 

flight appropriately. Once applied, this new course is called 

the magnetic course. 

Magnetic Deviation

Because each aircraft has its own internal effect upon the 

onboard compass systems from its own localized magnetic 

influencers, the pilot must add or subtract these influencers 

based upon the direction he or she is flying. The application of 
15-8

Figure 15-11. Magnetized portions of the airplane cause the 

compass to deviate from its normal indications.

N 33 30 W 24 21

S 15 12

E

6 3

N 33 30

W 24 21

S 15 12

E 6 3

N 33 30

W 24 21

S 15 12

E 6 3

Magnetic North

Magnetic North Magnetic North

ic

ic ic

Figure 15-12. Compass deviation card.

For (Magnetic)

Steer (Compass)

For (Magnetic

Steer (Compass)

E

86

W

274

60

57

240

243

N

0

S

180

30

28

210

212

120

117

300

303

150

148

330

332

deviation (taken from a compass deviation card) compensates 

the magnetic course unique to that aircraft’s compass system 

(as affected by localized magnetic influencers) and it now 

becomes the compass course. Therefore, the compass course 

when followed (in a no wind condition) takes the aircraft from 

point A to point B even though the aircraft heading may not 

match the original course line drawn on the chart. 

If the variation is shown as “9° E,” this means that magnetic 

north is 9° east of true north. If a true course of 360° is to be 

flown, 9° must be subtracted from 360°, which results in a 

magnetic heading of 351°. To fly east, a magnetic course of 

081° (090° – 9°) would be flown. To fly south, the magnetic 

course would be 171° (180° – 9°). To fly west, it would be 

261° (270° – 9°). To fly a true heading of 060°, a magnetic 

course of 051° (060° – 9°) would be flown.

Remember, if variation is west, add; if east, subtract. One 

method for remembering whether to add or subtract variation 

is the phrase “east is least (subtract) and west is best (add).”

Deviation

Determining the magnetic heading is an intermediate step 

necessary to obtain the correct compass heading for the flight. 

To determine compass heading, a correction for deviation 

must be made. Because of magnetic influences within 

an aircraft such as electrical circuits, radio, lights, tools, 

engine, and magnetized metal parts, the compass needle is 

frequently deflected from its normal reading. This deflection 

is deviation. The deviation is different for each aircraft, and it 

also may vary for different headings in the same aircraft. For 

instance, if magnetism in the engine attracts the north end of 

the compass, there would be no effect when the plane is on a 

heading of magnetic north. On easterly or westerly headings, 

however, the compass indications would be in error, as shown 

in Figure 15-11. Magnetic attraction can come from many 

other parts of the aircraft; the assumption of attraction in the 

engine is merely used for the purpose of illustration.

Some adjustment of the compass, referred to as compensation, 

can be made to reduce this error, but the remaining correction 

must be applied by the pilot. 

Proper compensation of the compass is best performed by 

a competent technician. Since the magnetic forces within 

the aircraft change, because of landing shocks, vibration, 

mechanical work, or changes in equipment, the pilot should 

occasionally have the deviation of the compass checked. The 

procedure used to check the deviation (called “swinging the 

compass”) is briefly outlined. 

The aircraft is placed on a magnetic compass rose, the engine 

started, and electrical devices normally used (such as radio) 

are turned on. Tailwheel-type aircaft should be jacked up 

into flying position. The aircraft is aligned with magnetic 

north indicated on the compass rose and the reading shown 

on the compass is recorded on a deviation card. The aircraft 

is then aligned at 30° intervals and each reading is recorded. 

If the aircraft is to be flown at night, the lights are turned on 

and any significant changes in the readings are noted. If so, 

additional entries are made for use at night.

The accuracy of the compass can also be checked by 

comparing the compass reading with the known runway 

headings.

A deviation card, similar to Figure 15-12, is mounted near 

the compass, showing the addition or subtraction required to 

correct for deviation on various headings, usually at intervals 

of 30°. For intermediate readings, the pilot should be able to 

interpolate mentally with sufficient accuracy. For example, 

if the pilot needed the correction for 195° and noted the 

correction for 180° to be 0° and for 210° to be +2°, it could 

be assumed that the correction for 195° would be +1°. The 

magnetic heading, when corrected for deviation, is known 

as compass heading. 
15-9

Figure 15-13. Motion of the air affects the speed with which aircraft 

move over the Earth’s surface. Airspeed, the rate at which an 

aircraft moves through the air, is not affected by air motion.

090°

Groundspeed 120 knots

WINDS ARE CALM

090°

Groundspeed 140 knots

WINDS 270° AT 20 KNOTS

090°

Groundspeed 100 knots

WINDS 090° AT 20 KNOTS

Effect of Wind

The preceding discussion explained how to measure a true 

course on the aeronautical chart and how to make corrections 

for variation and deviation, but one important factor has not 

been considered—wind. As discussed in the study of the 

atmosphere, wind is a mass of air moving over the surface of 

the Earth in a definite direction. When the wind is blowing 

from the north at 25 knots, it simply means that air is moving 

southward over the Earth’s surface at the rate of 25 NM in 

1 hour.

Under these conditions, any inert object free from contact 

with the Earth is carried 25 NM southward in 1 hour. This 

effect becomes apparent when such things as clouds, dust, 

and toy balloons are observed being blown along by the wind. 

Obviously, an aircraft flying within the moving mass of air 

is similarly affected. Even though the aircraft does not float 

freely with the wind, it moves through the air at the same time 

the air is moving over the ground, thus is affected by wind. 

Consequently, at the end of 1 hour of flight, the aircraft is in 

a position which results from a combination of the following 

two motions:

• Movement of the air mass in reference to the ground

• Forward movement of the aircraft through the air 

mass 

Actually, these two motions are independent. It makes no 

difference whether the mass of air through which the aircraft 

is flying is moving or is stationary. A pilot flying in a 70- 

knot gale would be totally unaware of any wind (except for 

possible turbulence) unless the ground were observed. In 

reference to the ground, however, the aircraft would appear 

to fly faster with a tailwind or slower with a headwind, or to 

drift right or left with a crosswind.

As shown in Figure 15-13, an aircraft flying eastward at an 

airspeed of 120 knots in still air has a groundspeed (GS) 

exactly the same—120 knots. If the mass of air is moving 

eastward at 20 knots, the airspeed of the aircraft is not 

affected, but the progress of the aircraft over the ground is 

120 plus 20, or a GS of 140 knots. On the other hand, if the 

mass of air is moving westward at 20 knots, the airspeed of 

the aircraft remains the same, but GS becomes 120 minus 

20, or 100 knots.

Assuming no correction is made for wind effect, if an aircraft 

is heading eastward at 120 knots, and the air mass moving 

southward at 20 knots, the aircraft at the end of 1 hour is 

almost 120 miles east of its point of departure because of its 

progress through the air. It is 20 miles south because of the 

motion of the air. Under these circumstances, the airspeed 

remains 120 knots, but the GS is determined by combining 

the movement of the aircraft with that of the air mass. GS can 

be measured as the distance from the point of departure to 

the position of the aircraft at the end of 1 hour. The GS can 

be computed by the time required to fly between two points a 

known distance apart. It also can be determined before flight 

by constructing a wind triangle, which is explained later in 

this chapter. [Figure 15-14]

The direction in which the aircraft is pointing as it flies 

is heading. Its actual path over the ground, which is a 

combination of the motion of the aircraft and the motion of 

the air, is its track. The angle between the heading and the 

track is drift angle. If the aircraft heading coincides with the 

true course and the wind is blowing from the left, the track 

does not coincide with the true course. The wind causes the 

aircraft to drift to the right, so the track falls to the right of 

the desired course or true course. [Figure 15-15]
15-10

Figure 15-15. Effects of wind drift on maintaining desired course.

Heading

Wind

Track

Drift angle Desired course

Figure 15-16. Relationship between true, magnetic, and compass 

headings for a particular instance.

Heading

TN MN CN

TH-088°

MH-078°

CH-074°

VAR 10° E

DEV 4°

Figure 15-14. Aircraft flightpath resulting from its airspeed and direction, and the wind speed and direction.

Airspeed effect (1 hour)

20 knots

Distance covered over ground (1 hour)

The following method is used by many pilots to determine 

compass heading: after the TC is measured, and wind 

correction applied resulting in a TH, the sequence TH ± 

variation (V) = magnetic heading (MH) ± deviation (D) 

= compass heading (CH) is followed to arrive at compass 

heading. [Figure 15-16]

By determining the amount of drift, the pilot can counteract 

the effect of the wind and make the track of the aircraft 

coincide with the desired course. If the mass of air is moving 

across the course from the left, the aircraft drifts to the 

right, and a correction must be made by heading the aircraft 

sufficiently to the left to offset this drift. To state in another 

way, if the wind is from the left, the correction is made by 

pointing the aircraft to the left a certain number of degrees, 

therefore correcting for wind drift. This is the wind correction 

angle (WCA) and is expressed in terms of degrees right or 

left of the true course. [Figure 15-17]
15-11

Figure 15-17. Establishing a wind correction angle that will counteract wind drift and maintain the desired course.

Heading

Wind

Track

Wind

correction

angle

Desired course

090°

075°

To summarize:

• Course—intended path of an aircraft over the ground 

or the direction of a line drawn on a chart representing 

the intended aircraft path, expressed as the angle 

measured from a specific reference datum clockwise 

from 0° through 360° to the line. 

• Heading—direction in which the nose of the aircraft 

points during flight.

• Track—actual path made over the ground in flight. (If 

proper correction has been made for the wind, track 

and course are identical.) 

• Drift angle—angle between heading and track.

• WCA—correction applied to the course to establish 

a heading so that track coincides with course. 

• Airspeed—rate of the aircraft’s progress through the 

air.

• GS—rate of the aircraft’s inflight progress over the 

ground.

Basic Calculations

Before a cross-country flight, a pilot should make common 

calculations for time, speed, and distance, and the amount 

of fuel required.

Converting Minutes to Equivalent Hours

Frequently, it is necessary to convert minutes into equivalent 

hours when solving speed, time, and distance problems. To 

convert minutes to hours, divide by 60 (60 minutes = 1 hour). 

Thus, 30 minutes is 30/60 = 0.5 hour. To convert hours to 

minutes, multiply by 60. Thus, 0.75 hour equals 0.75 x 60 

= 45 minutes.

Time T = D/GS

To find the time (T) in flight, divide the distance (D) by the 

GS. The time to fly 210 NM at a GS of 140 knots is 210 ÷ 

140, or 1.5 hours. (The 0.5 hour multiplied by 60 minutes 

equals 30 minutes.) Answer: 1:30.

Distance D = GS X T

To find the distance flown in a given time, multiply GS by 

time. The distance flown in 1 hour 45 minutes at a GS of 120 

knots is 120 x 1.75, or 210 NM.

GS GS = D/T

To find the GS, divide the distance flown by the time required. 

If an aircraft flies 270 NM in 3 hours, the GS is 270 ÷ 3 = 

90 knots.

Converting Knots to Miles Per Hour

Another conversion is that of changing knots to miles per hour 

(mph). The aviation industry is using knots more frequently 

than mph, but it might be well to discuss the conversion for 

those that use mph when working with speed problems. The 

NWS reports both surface winds and winds aloft in knots. 

However, airspeed indicators in some aircraft are calibrated 

in mph (although many are now calibrated in both miles per 

hour and knots). Pilots, therefore, should learn to convert 

wind speeds that are reported in knots to mph.

A knot is 1 nautical mile per hour (NMPH). Because there are 

6,076.1 feet in 1 NM and 5,280 feet in 1 SM, the conversion 

factor is 1.15. To convert knots to miles per hour, multiply 

speed in knots by 1.15. For example: a wind speed of 20 

knots is equivalent to 23 mph. 

Most flight computers or electronic calculators have a 

means of making this conversion. Another quick method of 

conversion is to use the scales of NM and SM at the bottom 

of aeronautical charts.
15-12

Fuel Consumption

Aircraft fuel consumption is computed in gallons per hour. 

Consequently, to determine the fuel required for a given 

flight, the time required for the flight must be known. Time 

in flight multiplied by rate of consumption gives the quantity 

of fuel required. For example, a flight of 400 NM at a GS of 

100 knots requires 4 hours. If an aircraft consumes 5 gallons 

an hour, the total consumption is 4 x 5, or 20 gallons.

The rate of fuel consumption depends on many factors: 

condition of the engine, propeller/rotor pitch, propeller/rotor 

revolutions per minute (rpm), richness of the mixture, and 

particularly the percentage of horsepower used for flight 

at cruising speed. The pilot should know the approximate 

consumption rate from cruise performance charts, or from 

experience. In addition to the amount of fuel required for the 

flight, there should be sufficient fuel for reserve.

Flight Computers

Up to this point, only mathematical formulas have been 

used to determine such items as time, distance, speed, and 

fuel consumption. In reality, most pilots use a mechanical 

or electronic flight computer. These devices can compute 

numerous problems associated with flight planning and 

navigation. The mechanical or electronic computer has an 

instruction book that probably includes sample problems so 

the pilot can become familiar with its functions and operation. 

[Figure 15-18]

Plotter

Another aid in flight planning is a plotter, which is a 

protractor and ruler. The pilot can use this when determining 

true course and measuring distance. Most plotters have a ruler 

which measures in both NM and SM and has a scale for a 

sectional chart on one side and a world aeronautical chart on 

the other. [Figure 15-18]

Pilotage

Pilotage is navigation by reference to landmarks or 

checkpoints. It is a method of navigation that can be used 

on any course that has adequate checkpoints, but it is more 

commonly used in conjunction with dead reckoning and 

VFR radio navigation.

The checkpoints selected should be prominent features 

common to the area of the flight. Choose checkpoints that can 

be readily identified by other features such as roads, rivers, 

railroad tracks, lakes, and power lines. If possible, select 

features that make useful boundaries or brackets on each 

side of the course, such as highways, rivers, railroads, and 

mountains. A pilot can keep from drifting too far off course 

by referring to and not crossing the selected brackets. Never 

place complete reliance on any single checkpoint. Choose 

ample checkpoints. If one is missed, look for the next one 

while maintaining the heading. When determining position 

from checkpoints, remember that the scale of a sectional chart 

is 1 inch = 8 SM or 6.86 NM. For example, if a checkpoint 

selected was approximately one-half inch from the course 

line on the chart, it is 4 SM or 3.43 NM from the course on 

the ground. In the more congested areas, some of the smaller 

features are not included on the chart. If confused, hold the 

heading. If a turn is made away from the heading, it is easy 

to become lost.

Roads shown on the chart are primarily the well-traveled 

roads or those most apparent when viewed from the air. 

New roads and structures are constantly being built, and 

may not be shown on the chart until the next chart is issued. 

Some structures, such as antennas may be difficult to see. 

Sometimes TV antennas are grouped together in an area near 

a town. They are supported by almost invisible guy wires. 

Never approach an area of antennas less than 500 feet above 

the tallest one. Most of the taller structures are marked with 

strobe lights to make them more visible to a pilot. However, 

some weather conditions or background lighting may make 

them difficult to see. Aeronautical charts display the best 

information available at the time of printing, but a pilot should 

be cautious for new structures or changes that have occurred 

since the chart was printed.

Dead Reckoning

Dead reckoning is navigation solely by means of computations 

based on time, airspeed, distance, and direction. The products 

derived from these variables, when adjusted by wind speed 

and velocity, are heading and GS. The predicted heading takes 

the aircraft along the intended path and the GS establishes the 

time to arrive at each checkpoint and the destination. Except 

for flights over water, dead reckoning is usually used with 

pilotage for cross-country flying. The heading and GS as 

calculated is constantly monitored and corrected by pilotage 

as observed from checkpoints.

The Wind Triangle or Vector Analysis

If there is no wind, the aircraft’s ground track is the same as 

the heading and the GS is the same as the true airspeed. This 

condition rarely exists. A wind triangle, the pilot’s version 

of vector analysis, is the basis of dead reckoning.

The wind triangle is a graphic explanation of the effect of 

wind upon flight. GS, heading, and time for any flight can be 

determined by using the wind triangle. It can be applied to 

the simplest kind of cross-country flight as well as the most 

complicated instrument flight. The experienced pilot becomes 

so familiar with the fundamental principles that estimates can 

be made which are adequate for visual flight without actually 

drawing the diagrams. The beginning student, however, needs 
15-13

INSTRUCTIONS FOR USE

1. Place hole over intersection of true course and true north line.

2. Without changing position rotate plotter until edge is over true course line.

3. From hole follow true north line to curved scale with arrow pointing in direction of flight.

4. Read true course in degrees, on proper scale, over true north line. read scales counter-clockwise.

SECTIONAL CHART SIDE - 1:500,000 NAVIGATIONAL FLIGHT PLOTTER

0 

180 

270 

90

10 

190 

280 

100 

20

200 

290 

110 

30 

210 

330 

150 

340 

160 

350 

170 

300 

120 

310 

130 

320 

140 

330

150 

34

1

0

60

350 

170 

190 

10 

200 

20

210 

30 

220

40

230

50

240

60

250

70

260

80

NAUTICAL 5 MILES 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 NAUTICAL 85 MILES

0 STATUTE 5 MILES 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 

DEGREES

Mode On/Off Clr

Dist Vol Wt Wx ÷

: 7 8 9 x

Sto 4 5 6 −

Rcl 1 2 3 +

Bksp 0 . +/- =

C

M

P

TSD Alt: As Wind Wt. Bal Timer

Conv: Dist Vol Wt Wx

A Plotter

B Mechanical Flight Computer

C Electronic Flight Computer

Figure 15-18. A plotter (A), the computational and wind side of a mechanical flight computer (B), and an electronic flight computer 

(C).

to develop skill in constructing these diagrams as an aid to the 

complete understanding of wind effect. Either consciously or 

unconsciously, every good pilot thinks of the flight in terms 

of wind triangle. 

If flight is to be made on a course to the east, with a wind 

blowing from the northeast, the aircraft must be headed 

somewhat to the north of east to counteract drift. This can 

be represented by a diagram as shown in Figure 15-19. Each 

line represents direction and speed. The long blue and white 

hashed line shows the direction the aircraft is heading, and 

its length represents the distance the airspeed for 1 hour. The 

short blue arrow at the right shows the wind direction, and 

its length represents the wind velocity for 1 hour. The solid 

yellow line shows the direction of the track or the path of the 

aircraft as measured over the earth, and its length represents 

the distance traveled in 1 hour, or the GS.

In actual practice, the triangle illustrated in Figure 15-19 is 

not drawn; instead, construct a similar triangle as shown by 

the blue, yellow, and black lines in Figure 15-20, which is 

explained in the following example.

Suppose a flight is to be flown from E to P. Draw a line on 

the aeronautical chart connecting these two points; measure 

its direction with a protractor, or plotter, in reference to a 

meridian. This is the true course, which in this example is 

assumed to be 090° (east). From the NWS, it is learned that 
15-14

Heading and airspeed

Course and groundspeed

N 33 30 W

24 21

S 15 12

E

6 3

P

W

E

Wind direction and velocity

N

S

Figure 15-20. The wind triangle as is drawn in navigation practice.

080° heading and 120 knots airspeed

090° course and 110 knots groundspeed

N 33 30 W 24 21

S 15 12

E

6 3

 Wind at 20°

 direction and 

 35 knots velocity

N

S

10° 

Drift Angle

8° left correction

Figure 15-19. Principle of the wind triangle.

the wind at the altitude of the intended flight is 40 knots from 

the northeast (045°). Since the NWS reports the wind speed in 

knots, if the true airspeed of the aircraft is 120 knots, there is 

no need to convert speeds from knots to mph or vice versa.

Now, on a plain sheet of paper draw a vertical line 

representing north to south. (The various steps are shown 

in Figure 15-21.) 

Step 1

Place the protractor with the base resting on the vertical line 

and the curved edge facing east. At the center point of the 

base, make a dot labeled “E” (point of departure), and at the 

curved edge, make a dot at 90° (indicating the direction of the 

true course) and another at 45° (indicating wind direction). 

Step 2

With the ruler, draw the true course line from E, extending 

it somewhat beyond the dot by 90°, and labeling it “TC 

090°.”

Step 3

Next, align the ruler with E and the dot at 45°, and draw the 

wind arrow from E, not toward 045°, but downwind in the 

direction the wind is blowing, making it 40 units long, to 

correspond with the wind velocity of 40 knots. Identify this 

line as the wind line by placing the letter “W” at the end to 

show the wind direction. 

Step 4

Finally, measure 120 units on the ruler to represent the 

airspeed, making a dot on the ruler at this point. The units 

used may be of any convenient scale or value (such as 1⁄4 inch 

= 10 knots), but once selected, the same scale must be used 

for each of the linear movements involved. Then place the 

ruler so that the end is on the arrowhead (W) and the 120-

knot dot intercepts the true course line. Draw the line and 

label it “AS 120.” The point “P” placed at the intersection 

represents the position of the aircraft at the end of 1 hour. 

The diagram is now complete. 
15-15

Figure 15-21. Steps in drawing the wind triangle. 90 80 70 60 50 40 30 20 10

071 160 150 140 130 120 110 100 

Airspeed 120 knots

TC 090° GS 88

N 33 30 W 24 21

S 15 12

E

6 3

P

W

E

N

S

50

 40

90 0

10

W

E

N

S

TC 090°

Wind

Mid Point

STEP 1

STEP 4

STEP 2 and 3 45°

90°

Figure 15-22. Finding true heading by the wind correction angle. 90 80 70 60 50 40 30 20 10

071 160 150 140 130 120 110 100

TH 076° AS 120

TC 090° GS 88

P

W

E

N

S

80

70

76°

The distance flown in 1 hour (GS) is measured as the numbers 

of units on the true course line (88 NMPH, or 88 knots). 

The true heading necessary to offset drift is indicated by the 

direction of the airspeed line, which can be determined in 

one of two ways:

• By placing the straight side of the protractor along the 

north-south line, with its center point at the intersection 

of the airspeed line and north-south line, read the true 

heading directly in degrees (076°). [Figure 15-22]

• By placing the straight side of the protractor along 

the true course line, with its center at P, read the angle 

between the true course and the airspeed line. This is 

the WCA, which must be applied to the true course 

to obtain the true heading. If the wind blows from the 

right of true course, the angle is added; if from the 

left, it is subtracted. In the example given, the WCA 

is 14° and the wind is from the left; therefore, subtract 

14° from true course of 090°, making the true heading 

076°. [Figure 15-23]
15-16

Figure 15-23. Finding true heading by direct measurement.

90 08 07 06 50 40 30 20 10

170 160 150 140 130 21 0 11 0 0 10

TH 076° AS 120

TC 090° GS 88

P

W

E

N

S

10 

20 

14°

WCA =14° L

After obtaining the true heading, apply the correction for 

magnetic variation to obtain magnetic heading, and the 

correction for compass deviation to obtain a compass 

heading. The compass heading can be used to fly to the 

destination by dead reckoning.

To determine the time and fuel required for the flight, first 

find the distance to destination by measuring the length of 

the course line drawn on the aeronautical chart (using the 

appropriate scale at the bottom of the chart). If the distance 

measures 220 NM, divide by the GS of 88 knots, which gives 

2.5 hours, or 2:30, as the time required. If fuel consumption 

is 8 gallons an hour, 8 x 2.5 or about 20 gallons is used. 

Briefly summarized, the steps in obtaining flight information 

are as follows:

• TC—direction of the line connecting two desired 

points, drawn on the chart and measured clockwise 

in degrees from true north on the mid-meridian.

• WCA—determined from the wind triangle. (Added 

to TC if the wind is from the right; subtracted if wind 

is from the left).

• TH—direction measured in degrees clockwise from 

true north, in which the nose of the plane should point 

to make good the desired course.

• Variation—obtained from the isogonic line on the chart 

(added to TH if west; subtracted if east).

• MH—an intermediate step in the conversion (obtained 

by applying variation to true heading).

• Deviation—obtained from the deviation card on 

the aircraft (added to MH or subtracted from, as 

indicated).

• Compass heading—reading on the compass (found by 

applying deviation to MH) which is followed to make 

good the desired course.

• Total distance—obtained by measuring the length of 

the TC line on the chart (using the scale at the bottom 

of the chart).

• GS—obtained by measuring the length of the TC line 

on the wind triangle (using the scale employed for 

drawing the diagram).

• Estimated time en route (ETE)—total distance divided 

by GS.

• Fuel rate—predetermined gallons per hour used at 

cruising speed.

NOTE: Additional fuel for adequate reserve should be added 

as a safety measure.

Flight Planning

Title 14 of the Code of Federal Regulations (14 CFR) part 

91 states, in part, that before beginning a flight, the pilot in 

command (PIC) of an aircraft shall become familiar with all 

available information concerning that flight. For flights not 

in the vicinity of an airport, this must include information 

on available current weather reports and forecasts, fuel 

requirements, alternatives available if the planned flight 

cannot be completed, and any known traffic delays of which 

the pilot in command has been advised by ATC.

Assembling Necessary Material

The pilot should collect the necessary material well before the 

flight. An appropriate current sectional chart and charts for 
15-17

Figure 15-24. Airport/Facility Directory.

areas adjoining the flight route should be among this material 

if the route of flight is near the border of a chart. 

Additional equipment should include a flight computer or 

electronic calculator, plotter, and any other item appropriate 

to the particular flight. For example, if a night flight is to 

be undertaken, carry a flashlight; if a flight is over desert 

country, carry a supply of water and other necessities.

Weather Check

It is wise to check the weather before continuing with other 

aspects of flight planning to see, first of all, if the flight is 

feasible and, if it is, which route is best. Chapter 12, Aviation 

Weather Services, discusses obtaining a weather briefing.

Use of Airport/Facility Directory (A/FD)

Study available information about each airport at which a 

landing is intended. This should include a study of the Notices 

to Airmen (NOTAMs) and the A/FD. [Figure 15-24] This 

includes location, elevation, runway and lighting facilities, 

available services, availability of aeronautical advisory 

station frequency (UNICOM), types of fuel available (use 

to decide on refueling stops), AFSS/FSS located on the 

airport, control tower and ground control frequencies, traffic 

information, remarks, and other pertinent information. The 

NOTAMs, issued every 28 days, should be checked for 

additional information on hazardous conditions or changes 

that have been made since issuance of the A/FD.

The sectional chart bulletin subsection should be checked for 

major changes that have occurred since the last publication 

date of each sectional chart being used. Remember, the 

chart may be up to 6 months old. The effective date of the 

chart appears at the top of the front of the chart. The A/FD 

generally has the latest information pertaining to such matters 

and should be used in preference to the information on the 

back of the chart, if there are differences.

Airplane Flight Manual or Pilot’s Operating 

Handbook (AFM/POH)

The Aircraft Flight Manual or Pilot’s Operating Handbook 

(AFM/POH) should be checked to determine the proper 

loading of the aircraft (weight and balance data). The weight 

of the usable fuel and drainable oil aboard must be known. 

Also, check the weight of the passengers, the weight of all 

baggage to be carried, and the empty weight of the aircraft to 

be sure that the total weight does not exceed the maximum 

allowable. The distribution of the load must be known to tell 

if the resulting center of gravity (CG) is within limits. Be 

sure to use the latest weight and balance information in the 

FAA-approved AFM or other permanent aircraft records, as 

appropriate, to obtain empty weight and empty weight CG 

information. 

Determine the takeoff and landing distances from the 

appropriate charts, based on the calculated load, elevation 

of the airport, and temperature; then compare these distances 

with the amount of runway available. Remember, the 

heavier the load and the higher the elevation, temperature, 

or humidity, the longer the takeoff roll and landing roll and 

the lower the rate of climb.

Check the fuel consumption charts to determine the rate of 

fuel consumption at the estimated flight altitude and power 

settings. Calculate the rate of fuel consumption, and then 

compare it with the estimated time for the flight so that 

refueling points along the route can be included in the plan.

Charting the Course

Once the weather has been checked and some preliminary 

planning done, it is time to chart the course and determine the 

data needed to accomplish the flight. The following sections 

provide a logical sequence to follow in charting the course, 

filling out a flight log, and filing a flight plan. In the following 

example, a trip is planned based on the following data and 

the sectional chart excerpt in Figure 15-25.
15-18

Figure 15-25. Sectional chart excerpt.

Checkpoint

Checkpoint

Checkpoint

Checkpoint

A

B Class C Airspace

C Class D Airspace

D Tallest obstruction

Highest elevation E

F

1

2

3

4

Route of flight: Chickasha Airport direct to Guthrie Airport

True airspeed (TAS) . . . . . . . . . . . . . . . . . . . . . 115 knots

Winds aloft . . . . . . . . . . . . . . . . . . . . . . . 360° at 10 knots

Usable fuel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 gallons

Fuel rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 GPH

Deviation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +2°

R

Course line
15-19

Figure 15-26. Pilot’s planning sheet and visual flight log.

PILOT’S PLANNING SHEET

COURSE TC TH MH DEV CH GS

From

To

From

To

Wind

Knots From

WCA

R+ LWCAR+ LTOTALMILES

TOTAL

TIME

FUEL

RATE

TOTAL

FUEL

PLANE IDENTIFICATION DATE

 Chickasha

Guthrie

031° 10 360° 3° L 28 7° E 21° +2° 23 53 106 kts 35 min 8 GPH 38 gal

N123DB

VISUAL FLIGHT LOG

WEATHER

AIRSPACE ETC.

POINT OF

DEPARTURE

Chickasha Airport

Guthrie Airport

TIME OF

DEPARTURE

DESTINATION

COURSE DISTANCE ELAPSED TIME GS CH REMARKS

NAVAID

IDENT.

FREQ.

NAVIGATION

AIDS

CHECKPOINT

#1

CHECKPOINT

#2

CHECKPOINT

#3

CHECKPOINT

#4

TO

FROM POINT TO POINT

CUMULATIVE

ACTUAL

ESTIMATED

ACTUAL

ESTIMATED

ACTUAL

ESTIMATED

11 NM

10 NM

10.5 NM

13 NM

8.5 NM

6 min

+5

6 min

6 min

7 min

5 min

106 kts

106 kts

106 kts

106 kts

023°

023°

023°

023°

21 NM

31.5 NM

44.5 NM

53 NM

Route of flight: Chickasha Airport direct to Guthrie 

Airport

 True airspeed (TAS)........................................115 knots

 Winds aloft...........................................360° at 10 knots

 Usable fuel.....................................................38 gallons

 Fuel rate...............................................................8 GPH

 Deviation..................................................................+2°

Steps in Charting the Course

The following is a suggested sequence for arriving at 

the pertinent information for the trip. As information is 

determined, it may be noted as illustrated in the example of 

a flight log in Figure 15-26. Where calculations are required, 

the pilot may use a mathematical formula or a manual or 

electronic flight computer. If unfamiliar with the use of a 

manual or electronic computer, it would be advantageous to 

read the operation manual and work several practice problems 

at this point.

First draw a line from Chickasha Airport (point A) directly 

to Guthrie Airport (point F). The course line should begin at 

the center of the airport of departure and end at the center of 

the destination airport. If the route is direct, the course line 

consists of a single straight line. If the route is not direct, it 

consists of two or more straight line segments. For example, 

a VOR station which is off the direct route, but which 

makes navigating easier, may be chosen (radio navigation 

is discussed later in this chapter).

Appropriate checkpoints should be selected along the route 

and noted in some way. These should be easy-to-locate points 

such as large towns, large lakes and rivers, or combinations of 

recognizable points such as towns with an airport, towns with 

a network of highways, and railroads entering and departing. 

Normally, choose only towns indicated by splashes of yellow 

on the chart. Do not choose towns represented by a small 

circle—these may turn out to be only a half-dozen houses. (In 

isolated areas, however, towns represented by a small circle 

can be prominent checkpoints.) For this trip, four checkpoints 

have been selected. Checkpoint 1 consists of a tower located 

east of the course and can be further identified by the highway 

and railroad track, which almost parallels the course at this 

point. Checkpoint 2 is the obstruction just to the west of the 

course and can be further identified by Will Rogers World 
15-20

Airport which is directly to the east. Checkpoint 3 is Wiley 

Post Airport, which the aircraft should fly directly over. 

Checkpoint 4 is a private, non-surfaced airport to the west of 

the course and can be further identified by the railroad track 

and highway to the east of the course.

The course and areas on either side of the planned route 

should be checked to determine if there is any type of airspace 

with which the pilot should be concerned or which has 

special operational requirements. For this trip, it should be 

noted that the course passes through a segment of the Class 

C airspace surrounding Will Rogers World Airport where the 

floor of the airspace is 2,500 feet mean sea level (MSL) and 

the ceiling is 5,300 feet MSL (point B). Also, there is Class 

D airspace from the surface to 3,800 feet MSL surrounding 

Wiley Post Airport (point C) during the time the control 

tower is in operation.

Study the terrain and obstructions along the route. This is 

necessary to determine the highest and lowest elevations 

as well as the highest obstruction to be encountered so that 

an appropriate altitude which conforms to 14 CFR part 91 

regulations can be selected. If the flight is to be flown at an 

altitude more than 3,000 feet above the terrain, conformance 

to the cruising altitude appropriate to the direction of flight 

is required. Check the route for particularly rugged terrain so 

it can be avoided. Areas where a takeoff or landing is made 

should be carefully checked for tall obstructions. Television 

transmitting towers may extend to altitudes over 1,500 feet 

above the surrounding terrain. It is essential that pilots be 

aware of their presence and location. For this trip, it should 

be noted that the tallest obstruction is part of a series of 

antennas with a height of 2,749 feet MSL (point D). The 

highest elevation should be located in the northeast quadrant 

and is 2,900 feet MSL (point E).

Since the wind is no factor and it is desirable and within the 

aircraft’s capability to fly above the Class C and D airspace 

to be encountered, an altitude of 5,500 feet MSL is chosen. 

This altitude also gives adequate clearance of all obstructions 

as well as conforms to the 14 CFR part 91 requirement to 

fly at an altitude of odd thousand plus 500 feet when on a 

magnetic course between 0 and 179°. 

Next, the pilot should measure the total distance of the 

course as well as the distance between checkpoints. The total 

distance is 53 NM and the distance between checkpoints is 

as noted on the flight log in Figure 15-26.

After determining the distance, the true course should be 

measured. If using a plotter, follow the directions on the 

plotter. The true course is 031°. Once the true heading is 

established, the pilot can determine the compass heading. 

This is done by following the formula given earlier in this 

chapter. The formula is:

TC ± WCA = TH ± V = MH ± D = CH

The WCA can be determined by using a manual or electronic 

flight computer. Using a wind of 360° at 10 knots, it is 

determined the WCA is 3° left. This is subtracted from the 

TC making the TH 28°. Next, the pilot should locate the 

isogonic line closest to the route of the flight to determine 

variation. Figure 15-25 shows the variation to be 6.30° E 

(rounded to 7° E), which means it should be subtracted from 

the TH, giving an MH of 21°. Next, add 2° to the MH for 

the deviation correction. This gives the pilot the compass 

heading which is 23°.

Now, the GS can be determined. This is done using a manual 

or electronic calculator. The GS is determined to be 106 

knots. Based on this information, the total trip time, as well 

as time between checkpoints, and the fuel burned can be 

determined. These calculations can be done mathematically 

or by using a manual or electronic calculator.

For this trip, the GS is 106 knots and the total time is 35 

minutes (30 minutes plus 5 minutes for climb) with a fuel 

burn of 4.7 gallons. Refer to the flight log in Figure 15-26

for the time between checkpoints.

As the trip progresses, the pilot can note headings and time 

and make adjustments in heading, GS, and time.

Filing a VFR Flight Plan

Filing a flight plan is not required by regulations; however, it 

is a good operating practice, since the information contained 

in the flight plan can be used in search and rescue in the event 

of an emergency.

Flight plans can be filed in the air by radio, but it is best to 

file a flight plan by phone just before departing. After takeoff, 

contact the AFSS by radio and give them the takeoff time so 

the flight plan can be activated. 

When a VFR flight plan is filed, it is held by the AFSS until 

1 hour after the proposed departure time and then canceled 

unless: the actual departure time is received; a revised 

proposed departure time is received; or at the time of filing, 

the AFSS is informed that the proposed departure time is 

met, but actual time cannot be given because of inadequate 

communication. The FSS specialist who accepts the flight 

plan does not inform the pilot of this procedure, however. 
15-21

Figure 15-27. Flight plan form.

X

N123DB C150/X 115 CHK, CHICKASHA 

AIRPORT 1400 5500

Chickasha direct Guthrie

GOK, Guthrie Airport

Guthrie, OK 35

4 45 1

Jane Smith

Aero Air, Oklahoma City, OK (405) 555-4149

Red/White

McAlester

Figure 15-27 shows the flight plan form a pilot files with the 

AFSS. When filing a flight plan by telephone or radio, give 

the information in the order of the numbered spaces. This 

enables the AFSS specialist to copy the information more 

efficiently. Most of the fields are either self-explanatory or 

non-applicable to the VFR flight plan (such as item 13). 

However, some fields may need explanation.

• Item 3 is the aircraft type and special equipment. An 

example would be C-150/X, which means the aircraft 

has no transponder. A listing of special equipment 

codes is found in the Aeronautical Information Manual 

(AIM).

• Item 6 is the proposed departure time in UTC 

(indicated by the “Z”). 

• Item 7 is the cruising altitude. Normally, “VFR” can be 

entered in this block, since the pilot chooses a cruising 

altitude to conform to FAA regulations.

• Item 8 is the route of flight. If the flight is to be direct, 

enter the word “direct;” if not, enter the actual route 

to be followed such as via certain towns or navigation 

aids.

• Item 10 is the estimated time en route. In the sample 

flight plan, 5 minutes was added to the total time to 

allow for the climb.

• Item 12 is the fuel on board in hours and minutes. This 

is determined by dividing the total usable fuel aboard 

in gallons by the estimated rate of fuel consumption 

in gallons.

Remember, there is every advantage in filing a flight plan; 

but do not forget to close the flight plan on arrival. Do this 

by telephone to avoid radio congestion.

Radio Navigation

Advances in navigational radio receivers installed in aircraft, 

the development of aeronautical charts which show the exact 

location of ground transmitting stations and their frequencies, 

along with refined flight deck instrumentation make it 

possible for pilots to navigate with precision to almost any 

point desired. Although precision in navigation is obtainable 

through the proper use of this equipment, beginning pilots 

should use this equipment to supplement navigation by visual 

reference to the ground (pilotage). This method provides the 
15-22

Figure 15-28. VHF transmissions follow a line-of-sight course.

“A” and “B” Signal

Received

Neither “A” nor “B” 

Signal Received

Only “A” Signal Received Only “B” Signal Received

VOR

Station

“A”

VOR

Station

“B”

pilot with an effective safeguard against disorientation in the 

event of radio malfunction.

There are four radio navigation systems available for use for 

VFR navigation. These are:

• VHF Omnidirectional Range (VOR)

• Nondirectional Radio Beacon (NDB)

• Long Range Navigation (LORAN-C)

• Global Positioning System (GPS)

Very High Frequency (VHF) Omnidirectional 

Range (VOR)

The VOR system is present in three slightly different 

navigation aids (NAVAIDs): VOR, VOR/DME, and 

VORTAC. By itself it is known as a VOR, and it provides 

magnetic bearing information to and from the station. When 

DME is also installed with a VOR, the NAVAID is referred 

to as a VOR/DME. When military tactical air navigation 

(TACAN) equipment is installed with a VOR, the NAVAID 

is known as a VORTAC. DME is always an integral part of a 

VORTAC. Regardless of the type of NAVAID utilized (VOR, 

VOR/DME or VORTAC), the VOR indicator behaves the 

same. Unless otherwise noted, in this section, VOR, VOR/

DME and VORTAC NAVAIDs are all referred to hereafter 

as VORs.

The prefix “omni-” means all, and an omnidirectional range 

is a VHF radio transmitting ground station that projects 

straight line courses (radials) from the station in all directions. 

From a top view, it can be visualized as being similar to 

the spokes from the hub of a wheel. The distance VOR 

radials are projected depends upon the power output of the 

transmitter.

The course or radials projected from the station are referenced 

to magnetic north. Therefore, a radial is defined as a line of 

magnetic bearing extending outward from the VOR station. 

Radials are identified by numbers beginning with 001, 

which is 1° east of magnetic north, and progress in sequence 

through all the degrees of a circle until reaching 360. To aid 

in orientation, a compass rose reference to magnetic north is 

superimposed on aeronautical charts at the station location.

VOR ground stations transmit within a VHF frequency band 

of 108.0–117.95 MHz. Because the equipment is VHF, the 

signals transmitted are subject to line-of-sight restrictions. 

Therefore, its range varies in direct proportion to the altitude 

of receiving equipment. Generally, the reception range of 

the signals at an altitude of 1,000 feet above ground level 

(AGL) is about 40 to 45 miles. This distance increases with 

altitude. [Figure 15-28]

VORs and VORTACs are classed according to operational 

use. There are three classes:

• T (Terminal)

• L (Low altitude)

• H (High altitude)

The normal useful range for the various classes is shown in 

the following table:

VOR/VORTAC NAVAIDS

Normal Usable Altitudes and Radius Distances

 Distance

 Class Altitudes (Miles)

 T 12,000' and below 25

 L Below 18,000' 40

 H Below 14,500' 40

 H Within the conterminous 48 states

 only, between 14,500 and 17,999' 100

 H 18,000'—FL 450 130

 H 60,000'—FL 450 100

The useful range of certain facilities may be less than 50 miles. 

For further information concerning these restrictions, refer to 

the Communication/NAVAID Remarks in the A/FD.
15-23

Figure 15-29. VOR indicator.

OBS

N

E

S

W

3

33

24

21

15

12

30

6

TO N

A

V

OBS knob

CDI needle

Course index

Unreliable signal flag

TO/FROM indicator Approximately 2 degrees

in the VOR mode

The accuracy of course alignment of VOR radials is 

considered to be excellent. It is generally within plus or 

minus 1°. However, certain parts of the VOR receiver 

equipment deteriorate, and this affects its accuracy. This is 

particularly true at great distances from the VOR station. The 

best assurance of maintaining an accurate VOR receiver is 

periodic checks and calibrations. VOR accuracy checks are 

not a regulatory requirement for VFR flight. However, to 

assure accuracy of the equipment, these checks should be 

accomplished quite frequently and a complete calibration 

each year. The following means are provided for pilots to 

check VOR accuracy:

• FAA VOR test facility (VOT)

• Certified airborne checkpoints

• Certified ground checkpoints located on airport 

surfaces

If an aircraft has two VOR receivers installed, a dual VOR 

receiver check can be made. To accomplish the dual receiver 

check, a pilot tunes both VOR receivers to the same VOR 

ground facility. The maximum permissible variation between 

the two indicated bearings is 4 degrees. A list of the airborne 

and ground checkpoints is published in the A/FD.

Basically, these checks consist of verifying that the VOR 

radials the aircraft equipment receives are aligned with the 

radials the station transmits. There are not specific tolerances 

in VOR checks required for VFR flight. But as a guide to 

assure acceptable accuracy, the required IFR tolerances can 

be used—±4° for ground checks and ±6° for airborne checks. 

These checks can be performed by the pilot.

The VOR transmitting station can be positively identified 

by its Morse code identification or by a recorded voice 

identification which states the name of the station followed 

by “VOR.” Many FSS transmit voice messages on the same 

frequency that the VOR operates. Voice transmissions should 

not be relied upon to identify stations, because many FSS 

remotely transmit over several omniranges, which have 

names different from that of the transmitting FSS. If the VOR 

is out of service for maintenance, the coded identification is 

removed and not transmitted. This serves to alert pilots that 

this station should not be used for navigation. VOR receivers 

are designed with an alarm flag to indicate when signal 

strength is inadequate to operate the navigational equipment. 

This happens if the aircraft is too far from the VOR or the 

aircraft is too low and, therefore, is out of the line of sight 

of the transmitting signals.

Using the VOR

In review, for VOR radio navigation, there are two 

components required: ground transmitter and aircraft 

receiving equipment. The ground transmitter is located at a 

specific position on the ground and transmits on an assigned 

frequency. The aircraft equipment includes a receiver with 

a tuning device and a VOR or omninavigation instrument. 

The navigation instrument could be a course deviation 

indicator (CDI), horizontal situation indicator (HSI), or a 

radio magnetic indicator (RMI). Each of these instruments 

indicates the course to the tuned VOR. 

Course Deviation Indicator (CDI)

The CDI is found in most training aircraft. It consists of 

(1) omnibearing selector (OBS) sometimes referred to as 

the course selector, (2) a CDI needle (Left-Right Needle), 

and (3) a TO/FROM indicator.

The course selector is an azimuth dial that can be rotated to 

select a desired radial or to determine the radial over which 

the aircraft is flying. In addition, the magnetic course “TO” 

or “FROM” the station can be determined.

When the course selector is rotated, it moves the CDI or 

needle to indicate the position of the radial relative to the 

aircraft. If the course selector is rotated until the deviation 

needle is centered, the radial (magnetic course “FROM” the 

station) or its reciprocal (magnetic course “TO” the station) 

can be determined. The course deviation needle also moves 

to the right or left if the aircraft is flown or drifting away 

from the radial which is set in the course selector.

By centering the needle, the course selector indicates either 

the course “FROM” the station or the course “TO” the station. 

If the flag displays a “TO,” the course shown on the course 

selector must be flown to the station. [Figure 15-29] If 
15-24

Figure 15-30. Horizontal situation indicator.

33

30

24

2I

I5

I2

6

3

GS GS

DC

NAV HDG

Lubber line

Compass warning flag

Glideslope deviation scale

NAV warning flag

Course deviation bar

Heading select knob

Course select pointer

Compass card

Symbolic aircraft

Heading select bug

Course select knob

Dual glideslope pointers

To/From indicator Course deviation scale

Figure 15-31. Radio magnetic indicator.

33

30

24

21

15

12

6

3

S

W

E

N

HDG

A

D

F

A

D

F

NAV NAV

“FROM” is displayed and the course shown is followed, the 

aircraft is flown away from the station. 

Horizontal Situation Indicator

The HSI is a direction indicator that uses the output 

from a flux valve to drive the compass card. The HSI 

[Figure 15-30] combines the magnetic compass with 

navigation signals and a glideslope. The HSI gives the pilot 

an indication of the location of the aircraft with relationship 

to the chosen course or radial.

In Figure 15-30, the aircraft magnetic heading displayed 

on the compass card under the lubber line is 184°. The 

course select pointer shown is set to 295°; the tail of the 

pointer indicates the reciprocal, 115°. The course deviation 

bar operates with a VOR/Localizer (VOR/LOC) or GPS 

navigation receiver to indicate left or right deviations from 

the course selected with the course select pointer; operating 

in the same manner, the angular movement of a conventional 

VOR/LOC needle indicates deviation from course. 

The desired course is selected by rotating the course select 

pointer, in relation to the compass card, by means of the 

course select knob. The HSI has a fixed aircraft symbol 

and the course deviation bar displays the aircraft’s position 

relative to the selected course. The TO/FROM indicator is a 

triangular pointer. When the indicator points to the head of 

the course select pointer, the arrow shows the course selected. 

If properly intercepted and flown, the course will take the 

aircraft to the chosen facility. When the indicator points to the 

tail of the course, the arrow shows that the course selected, if 

properly intercepted and flown, will take the aircraft directly 

away from the chosen facility.

When the NAV warning flag appears it indicates no reliable 

signal is being received. The appearance of the HDG flag 

indicates the compass card is not functioning properly.

The glideslope pointer indicates the relation of the aircraft to 

the glideslope. When the pointer is below the center position, 

the aircraft is above the glideslope and an increased rate 

of descent is required. In some installations, the azimuth 

card is a remote indicating compass; however, in others the 

heading must be checked occasionally against the magnetic 

compass and reset.

Radio Magnetic Indicator (RMI)

The RMI [Figure 15-31] is a navigational aid providing 

aircraft magnetic or directional gyro heading and very high 

frequency omnidirectional range (VOR), GPS, and automatic 

direction finder (ADF) bearing information. Remote indicating 
15-25

Figure 15-32. Tracking a radial in a crosswind.

N

1. View 

pos

2. Mov

rese

turn

N

E

S

W

3

33

24 21

15 12

30

6

TO

OBS

33 30

24

2I

I5 I2

6 3

N

E

S

W

3

33

24 21

15 12

30

6

TO

OBS

33

30

24 2I

I5 I2

6 3

N

E

S

W

3

33

24 21

15 12

30

6

TO

OBS

33

30

24 2I

I5 I2

6 3

N

E

S

W

3

33

24 21

15 12

30

6

TO

OBS

33

30

24 I 2

I5 I2

6 3

N

E

S

W

3

33

24 21

15 12

30

6

TO

OBS

33

30

24 2I

I5 I2

6 3

N

E

S

W

3

33

24 21

15 12

30

6

FROM

OBS

33

30

24 2I

I5 I2

6 3

N

E

S

W

3

33

24 21

15 12

30

6

FROM

OBS

33

30

24 2I

I5 I2

6 3

N

E

W

S

3

33

24 12

15 12

30

6

FROM

OBS

33 30

24 2I

I5 I2

3 6

3

2

1

4

5

6

7

8

0

18

27

6

BRAVO

BRA 115.0

WIND

compasses were developed to compensate for errors in and 

limitations of older types of heading indicators.

The remote compass transmitter is a separate unit usually 

mounted in a wingtip to eliminate the possibility of magnetic 

interference. The RMI consists of a compass card, a heading 

index, two bearing pointers, and pointer function switches. 

The two pointers are driven by any two combinations of a 

GPS, an ADF, and/or a VOR. The pilot has the ability to 

select the navigation aid to be indicated. The pointer indicates 

course to selected NAVAID or waypoint. In Figure 15-31

the green pointer is indicating the station tuned on the ADF. 

The yellow pointer is indicating the course to a VOR of 

GPS waypoint. Note that there is no requirement for a pilot 

to select course with the RMI, but only the NAVAID is to 

be indicated. 

Tracking With VOR

The following describes a step-by-step procedure to use when 

tracking to and from a VOR station using a CDI. Figure 15-32

illustrates the procedure.

First, tune the VOR receiver to the frequency of the selected 

VOR station. For example, 115.0 to receive Bravo VOR. Next, 

check the identifiers to verify that the desired VOR is being 

received. As soon as the VOR is properly tuned, the course 

deviation needle deflects either left or right. Then, rotate the 

azimuth dial to the course selector until the course deviation 

needle centers and the TO-FROM indicator indicates “TO.” 

If the needle centers with a “FROM” indication, the azimuth 

should be rotated 180° because, in this case, it is desired to 

fly “TO” the station. Now, turn the aircraft to the heading 

indicated on the VOR azimuth dial or course selector, 350° 

in this example.

If a heading of 350° is maintained with a wind from the right 

as shown, the aircraft drifts to the left of the intended track. 

As the aircraft drifts off course, the VOR course deviation 

needle gradually moves to the right of center or indicates the 

direction of the desired radial or track.

To return to the desired radial, the aircraft heading must be 

altered to the right. As the aircraft returns to the desired track, 

the deviation needle slowly returns to center. When centered, 

the aircraft is on the desired radial and a left turn must be 

made toward, but not to the original heading of 350° because 

a wind drift correction must be established. The amount of 

correction depends upon the strength of the wind. If the wind 

velocity is unknown, a trial-and-error method can be used 

to find the correct heading. Assume, for this example, a 10° 

correction for a heading of 360° is maintained.
15-26

Figure 15-33. Time-distance check example.

= Time in seconds between bearings

Degrees of bearing change

Minutes to station

= 12 minutes to the station

Time-Distance Check Example

For example, if 2 minutes (120 seconds) is required to fly a 

bearing change of 10 degrees, the aircraft is—

120

10

While maintaining a heading of 360°, assume that the course 

deviation begins to move to the left. This means that the wind 

correction of 10° is too great and the aircraft is flying to the 

right of course. A slight turn to the left should be made to 

permit the aircraft to return to the desired radial.

When the deviation needle centers, a small wind drift 

correction of 5° or a heading correction of 355° should be 

flown. If this correction is adequate, the aircraft remains 

on the radial. If not, small variations in heading should be 

made to keep the needle centered, and consequently keep the 

aircraft on the radial.

As the VOR station is passed, the course deviation needle 

fluctuates, then settles down, and the “TO” indication 

changes to “FROM.” If the aircraft passes to one side of the 

station, the needle deflects in the direction of the station as 

the indicator changes to “FROM.”

Generally, the same techniques apply when tracking 

outbound as those used for tracking inbound. If the intent is 

to fly over the station and track outbound on the reciprocal of 

the inbound radial, the course selector should not be changed. 

Corrections are made in the same manner to keep the needle 

centered. The only difference is that the omnidirectional 

range indicator indicates “FROM.”

If tracking outbound on a course other than the reciprocal of 

the inbound radial, this new course or radial must be set in 

the course selector and a turn made to intercept this course. 

After this course is reached, tracking procedures are the same 

as previously discussed.

Tips on Using the VOR

• Positively identify the station by its code or voice 

identification.

• Keep in mind that VOR signals are “line-of-sight.” A 

weak signal or no signal at all is received if the aircraft 

is too low or too far from the station.

• When navigating to a station, determine the inbound 

radial and use this radial. Fly a heading that will 

maintain the course. If the aircraft drifts, fly a heading 

to re-intercept the course then apply a correction to 

compensate for wind drift.

• If minor needle fluctuations occur, avoid changing 

headings immediately. Wait momentarily to see if the 

needle recenters; if it does not, then correct.

• When flying “TO” a station, always fly the selected 

course with a “TO” indication. When flying “FROM” a 

station, always fly the selected course with a “FROM” 

indication. If this is not done, the action of the course 

deviation needle is reversed. To further explain this 

reverse action, if the aircraft is flown toward a station 

with a “FROM” indication or away from a station 

with a “TO” indication, the course deviation needle 

indicates in an direction opposite to that which it 

should indicate. For example, if the aircraft drifts to 

the right of a radial being flown, the needle moves to 

the right or points away from the radial. If the aircraft 

drifts to the left of the radial being flown, the needle 

moves left or in the direction opposite to the radial.

• When navigating using the VOR it is important to fly 

headings that maintain or re-intercept the course. Just 

turning toward the needle will cause overshooting 

the radial and flying an S turn to the left and right of 

course.

Time and Distance Check From a Station

To compute time and distance from a station, first turn the 

aircraft to place the bearing pointer on the nearest 90° index. 

Note time and maintain heading. When the bearing pointer 

has moved 10°, note the elapsed time in seconds and apply 

the formulas in the following example to determine time and 

distance. [Figure 15-33]

The time from station may also be calculated by using a short 

method based on the above formula, if a 10° bearing change 

is flown. If the elapsed time for the bearing change is noted 

in seconds and a 10° bearing change is made, the time from 

the station in minutes is determined by counting off one 

decimal point. Thus, if 75 seconds are required to fly a 10° 

bearing change, the aircraft is 7.5 minutes from the station. 

When the bearing pointer is moving rapidly or when several 

corrections are required to place the pointer on the wingtip 

position, the aircraft is at station passage.

The distance from the station is computed by multiplying TAS 

or GS (in miles per minute) by the previously determined time 

in minutes. For example, if the aircraft is 7.5 minutes from 

station, flying at a TAS of 120 knots or 2 NM per minute, the 

distance from station is 15 NM (7.5 x 2 = 15).
15-27

The preceding are methods of computing approximate time 

and distance. The accuracy of time and distance checks is 

governed by existing wind, degree of bearing change, and 

accuracy of timing. The number of variables involved causes 

the result to be only an approximation. However, by flying an 

accurate heading and checking the time and bearing closely, 

the pilot can make a reasonable estimate of time and distance 

from the station.

Course Intercept 

Course interceptions are performed in most phases of 

instrument navigation. The equipment used varies, but an 

intercept heading must be flown that results in an angle or 

rate of intercept sufficient to solve a particular problem.

Rate of Intercept

Rate of intercept, seen by the aviator as bearing pointer or 

HSI movement, is a result of the following factors:

• The angle at which the aircraft is flown toward a 

desired course (angle of intercept)

• True airspeed and wind (GS)

• Distance from the station

Angle of Intercept 

The angle of intercept is the angle between the heading of the 

aircraft (intercept heading) and desired course. Controlling 

this angle by selection/adjustment of the intercept heading 

is the easiest and most effective way to control course 

interceptions. Angle of intercept must be greater than the 

degrees from course, but should not exceed 90°. Within this 

limit, adjust to achieve the most desirable rate of intercept.

When selecting an intercept heading, the key factor is the 

relationship between distance from the station and degrees 

from the course. Each degree, or radial, is 1 NM wide at 

a distance of 60 NM from the station. Width increases or 

decreases in proportion to the 60 NM distance. For example, 

1 degree is 2 NM wide at 120 NM—and 1⁄2 NM wide at 30 

NM. For a given GS and angle of intercept, the resultant rate 

of intercept varies according to the distance from the station. 

When selecting an intercept heading to form an angle of 

intercept, consider the following factors:

• Degrees from course

• Distance from the station

• True airspeed and wind (GS)

Distance Measuring Equipment (DME)

Distance measuring equipment (DME) consists of an ultra 

high frequency (UHF) navigational aid with VOR/DMEs and 

VORTACs. It measures, in NM, the slant range distance of 

an aircraft from a VOR/DME or VORTAC (both hereafter 

referred to as a VORTAC). Although DME equipment is very 

popular, not all aircraft are DME equipped. 

To utilize DME, the pilot should select, tune, and identify 

a VORTAC, as previously described. The DME receiver, 

utilizing what is called a “paired frequency” concept, 

automatically selects and tunes the UHF DME frequency 

associated with the VHF VORTAC frequency selected by 

the pilot. This process is entirely transparent to the pilot. 

After a brief pause, the DME display shows the slant range 

distance to or from the VORTAC. Slant range distance is the 

direct distance between the aircraft and the VORTAC, and 

is therefore affected by aircraft altitude. (Station passage 

directly over a VORTAC from an altitude of 6,076 feet above 

ground level (AGL) would show approximately 1.0 NM on 

the DME.) DME is a very useful adjunct to VOR navigation. 

A VOR radial alone merely gives line of position information. 

With DME, a pilot may precisely locate the aircraft on that 

line (radial).

Most DME receivers also provide GS and time-to-station 

modes of operation. The GS is displayed in knots (NMPH). 

The time-to-station mode displays the minutes remaining to 

VORTAC station passage, predicated upon the present GS. 

GS and time-to-station information is only accurate when 

tracking directly to or from a VORTAC. DME receivers 

typically need a minute or two of stabilized flight directly to 

or from a VORTAC before displaying accurate GS or timeto-station information. 

Some DME installations have a hold feature that permits 

a DME signal to be retained from one VORTAC while the 

course indicator displays course deviation information from 

an ILS or another VORTAC.

VOR/DME RNAV

Area navigation (RNAV) permits electronic course guidance 

on any direct route between points established by the pilot. 

While RNAV is a generic term that applies to a variety of 

navigational aids, such as LORAN-C, GPS, and others, this 

section deals with VOR/DME-based RNAV. VOR/DME 

RNAV is not a separate ground-based NAVAID, but a 

method of navigation using VOR/DME and VORTAC 

signals specially processed by the aircraft’s RNAV computer. 

[Figure 15-34]

NOTE: In this section, the term “VORTAC” also includes 

VOR/DME NAVAIDs.

In its simplest form, VOR/DME RNAV allows the pilot to 

electronically move VORTACs around to more convenient 

locations. Once electronically relocated, they are referred 

to as waypoints. These waypoints are described as a 
15-28

Figure 15-35. RNAV controls.

3 3 4 2 7 9

BEARING LOAD DISTANCE

OFFSET EN ROUTE

R

N

A

V

3 3

4 4

8 8

12 12

Figure 15-34. Flying an RNAV course.

Area Navigation Direct Route

combination of a selected radial and distance within the 

service volume of the VORTAC to be used. These waypoints 

allow a straight course to be flown between almost any 

origin and destination, without regard to the orientation of 

VORTACs or the existence of airways. 

While the capabilities and methods of operation of VOR/

DME RNAV units differ, there are basic principles of 

operation that are common to all. Pilots are urged to study 

the manufacturer’s operating guide and receive instruction 

prior to the use of VOR/DME RNAV or any unfamiliar 

navigational system. Operational information and limitations 

should also be sought from placards and the supplement 

section of the AFM/POH.

VOR/DME-based RNAV units operate in at least three 

modes: VOR, en route, and approach. A fourth mode, VOR 

Parallel, may also be found on some models. The units need 

both VOR and DME signals to operate in any RNAV mode. 

If the NAVAID selected is a VOR without DME, RNAV 

mode will not function.

In the VOR (or non-RNAV) mode, the unit simply functions 

as a VOR receiver with DME capability. [Figure 15-35] The 

unit’s display on the VOR indicator is conventional in all 

respects. For operation on established airways or any other 

ordinary VOR navigation, the VOR mode is used.

To utilize the unit’s RNAV capability, the pilot selects and 

establishes a waypoint or a series of waypoints to define 

a course. To operate in any RNAV mode, the unit needs 

both radial and distance signals; therefore, a VORTAC (or 

VOR/DME) needs to be selected as a NAVAID. To establish 

a waypoint, a point somewhere within the service range of 

a VORTAC is defined on the basis of radial and distance. 

Once the waypoint is entered into the unit and the RNAV en 

route mode is selected, the CDI displays course guidance to 

the waypoint, not the original VORTAC. DME also displays 

distance to the waypoint. Many units have the capability to 

store several waypoints, allowing them to be programmed 

prior to flight, if desired, and called up in flight.

RNAV waypoints are entered into the unit in magnetic 

bearings (radials) of degrees and tenths (i.e., 275.5°) and 

distances in NM and tenths (i.e., 25.2 NM). When plotting 

RNAV waypoints on an aeronautical chart, pilots find it 

difficult to measure to that level of accuracy, and in practical 

application, it is rarely necessary. A number of flight planning 

publications publish airport coordinates and waypoints with 

this precision and the unit accepts those figures. There is a 

subtle, but important difference in CDI operation and display 

in the RNAV modes.

In the RNAV modes, course deviation is displayed in terms 

of linear deviation. In the RNAV en route mode, maximum 

deflection of the CDI typically represents 5 NM on either side 

of the selected course, without regard to distance from the 

waypoint. In the RNAV approach mode, maximum deflection 

of the CDI typically represents 11⁄4 NM on either side of the 

selected course. There is no increase in CDI sensitivity as the 

aircraft approaches a waypoint in RNAV mode.

The RNAV approach mode is used for instrument approaches. 

Its narrow scale width (1⁄4 of the en route mode) permits very 

precise tracking to or from the selected waypoint. In visual 

flight rules (VFR) cross-country navigation, tracking a course 

in the approach mode is not desirable because it requires a 

great deal of attention and soon becomes tedious.

A fourth, lesser-used mode on some units is the VOR Parallel 

mode. This permits the CDI to display linear (not angular) 

deviation as the aircraft tracks to and from VORTACs. 

It derives its name from permitting the pilot to offset (or 

parallel) a selected course or airway at a fixed distance of 

the pilot’s choosing, if desired. The VOR parallel mode 

has the same effect as placing a waypoint directly over an 

existing VORTAC. Some pilots select the VOR parallel 

mode when utilizing the navigation (NAV) tracking function 

of their autopilot for smoother course following near the 

VORTAC.

Confusion is possible when navigating an aircraft with VOR/

DME-based RNAV, and it is essential that the pilot become 
15-29

Figure 15-36. ADF with fixed azimuth and magnetic compass.

N-S E-W

33

30

24

21

15

12

3 6

W

S

E

N

familiar with the equipment installed. It is not unknown for 

pilots to operate inadvertently in one of the RNAV modes 

when the operation was not intended by overlooking switch 

positions or annunciators. The reverse has also occurred with 

a pilot neglecting to place the unit into one of the RNAV 

modes by overlooking switch positions or annunciators. 

As always, the prudent pilot is not only familiar with the 

equipment used, but never places complete reliance in just 

one method of navigation when others are available for 

cross-check.

Automatic Direction Finder (ADF)

Many general aviation-type aircraft are equipped with ADF 

radio receiving equipment. To navigate using the ADF, the 

pilot tunes the receiving equipment to a ground station known 

as a nondirectional radio beacon (NDB). The NDB stations 

normally operate in a low or medium frequency band of 

200 to 415 kHz. The frequencies are readily available on 

aeronautical charts or in the A/FD.

All radio beacons except compass locators transmit a 

continuous three-letter identification in code except during 

voice transmissions. A compass locator, which is associated 

with an instrument landing system, transmits a two-letter 

identification.

Standard broadcast stations can also be used in conjunction 

with ADF. Positive identification of all radio stations is 

extremely important and this is particularly true when using 

standard broadcast stations for navigation.

NDBs have one advantage over the VOR. This advantage is 

that low or medium frequencies are not affected by line-ofsight. The signals follow the curvature of the Earth; therefore, 

if the aircraft is within the range of the station, the signals 

can be received regardless of altitude.

The following table gives the class of NDB stations, their 

power, and usable range:

NONDIRECTIONAL RADIOBEACON (NDB)

(Usable Radius Distances for All Altitudes)

 Power Distance

Class (Watts) (Miles)

Compass Locator Under 25 15

MH Under 50 25

H 50–1999 *50

HH 2000 or more 75

*Service range of individual facilities may be less than 50 

miles.

One of the disadvantages that should be considered when 

using low frequency (LF) for navigation is that low frequency 

signals are very susceptible to electrical disturbances, such as 

lightning. These disturbances create excessive static, needle 

deviations, and signal fades. There may be interference from 

distant stations. Pilots should know the conditions under 

which these disturbances can occur so they can be more alert 

to possible interference when using the ADF.

Basically, the ADF aircraft equipment consists of a tuner, 

which is used to set the desired station frequency, and the 

navigational display. 

The navigational display consists of a dial upon which the 

azimuth is printed, and a needle which rotates around the dial 

and points to the station to which the receiver is tuned.

Some of the ADF dials can be rotated to align the 

azimuth with the aircraft heading; others are fixed with 0° 

representing the nose of the aircraft, and 180° representing 

the tail. Only the fixed azimuth dial is discussed in this 

handbook. [Figure 15-36]

Figure 15-37 illustrates terms that are used with the ADF 

and should be understood by the pilot. 

To determine the magnetic bearing “FROM” the station, 

180° is added to or subtracted from the magnetic bearing to 

the station. This is the reciprocal bearing and is used when 

plotting position fixes.
15-30

Figure 15-38. ADF tracking.

330° 33 30

24 12

15 12

6 3

W

S

E

N

330° 33 30

24 12

15 12

6 3

W

S

E

N

340° bearing to station

Figure 15-37. ADF terms.

Radio station

N-S E-W

33

30

24

21

15 21

6 3

W

S

E

N

Magnetic bearing to station

Relative bearing

Magnetic hea

Ma

ding

gnetic North

Keep in mind that the needle of fixed azimuth points to the 

station in relation to the nose of the aircraft. If the needle is 

deflected 30° to the left for a relative bearing of 330°, this 

means that the station is located 30° left. If the aircraft is 

turned left 30°, the needle moves to the right 30° and indicates 

a relative bearing of 0°, or the aircraft is pointing toward 

the station. If the pilot continues flight toward the station 

keeping the needle on 0°, the procedure is called homing to 

the station. If a crosswind exists, the ADF needle continues to 

drift away from zero. To keep the needle on zero, the aircraft 

must be turned slightly resulting in a curved flightpath to the 

station. Homing to the station is a common procedure, but 

results in drifting downwind, thus lengthening the distance 

to the station.

Tracking to the station requires correcting for wind drift and 

results in maintaining flight along a straight track or bearing 

to the station. When the wind drift correction is established, 

the ADF needle indicates the amount of correction to the 

right or left. For instance, if the magnetic bearing to the 

station is 340°, a correction for a left crosswind would 

result in a magnetic heading of 330°, and the ADF needle 

would indicate 10° to the right or a relative bearing of 010°. 

[Figure 15-38]

When tracking away from the station, wind corrections are 

made similar to tracking to the station, but the ADF needle 

points toward the tail of the aircraft or the 180° position on 

the azimuth dial. Attempting to keep the ADF needle on 

the 180° position during winds results in the aircraft flying 

a curved flight leading further and further from the desired 

track. To correct for wind when tracking outbound, correction 

should be made in the direction opposite of that in which the 

needle is pointing.

Although the ADF is not as popular as the VOR for radio 

navigation, with proper precautions and intelligent use, the 

ADF can be a valuable aid to navigation.

Loran-C Navigation

Long range navigation, version C (LORAN-C) is another 

form of RNAV, but one that operates from chains of 

transmitters broadcasting signals in the LF spectrum. World 

Aeronautical Chart (WAC), sectional charts, and VFR 

terminal area charts do not show the presence of LORANC transmitters. Selection of a transmitter chain is either 

made automatically by the unit, or manually by the pilot 

using guidance information provided by the manufacturer. 

LORAN-C is a highly accurate, supplemental form of 

navigation typically installed as an adjunct to VOR and 

ADF equipment. Databases of airports, NAVAIDs, and ATC 

facilities are frequently features of LORAN-C receivers. 
15-31

LORAN-C is an outgrowth of the original LORAN-A 

developed for navigation during World War II. The LORAN-C 

system is used extensively in maritime applications. It 

experienced a dramatic growth in popularity with pilots with 

the advent of the small, panel-mounted LORAN-C receivers 

available at relatively low cost. These units are frequently 

very sophisticated and capable, with a wide variety of 

navigational functions.

With high levels of LORAN-C sophistication and capability, 

a certain complexity in operation is an unfortunate necessity. 

Pilots are urged to read the operating handbooks and to 

consult the supplements section of the AFM/POH prior to 

utilizing LORAN-C for navigation. Many units offer so many 

features that the manufacturers often publish two different 

sets of instructions: (1) a brief operating guide and (2) indepth operating manual.

While coverage is not global, LORAN-C signals are suitable 

for navigation in all of the conterminous United States, and 

parts of Canada and Alaska. Several foreign countries also 

operate their own LORAN-C systems. In the United States, 

the U.S. Coast Guard operates the LORAN-C system. 

LORAN-C system status is available from: USCG Navigation 

Center, Alexandria, Virginia at (703) 313-5900.

LORAN-C absolute accuracy is excellent—position errors 

are typically less than .25 NM. Repeatable accuracy, or 

the ability to return to a waypoint previously visited, is 

even better. While LORAN-C is a form of RNAV, it differs 

significantly from VOR/DME-based RNAV. It operates in a 

90–110 kHz frequency range and is based upon measurement 

of the difference in arrival times of pulses of radio frequency 

(RF) energy emitted by a chain of transmitters hundreds of 

miles apart.

Within any given chain of transmitters, there is a master 

station, and from three to five secondary stations. LORANC units must be able to receive at least a master and two 

secondary stations to provide navigational information. 

Unlike VOR/DME-based RNAV, where the pilot must select 

the appropriate VOR/DME or VORTAC frequency, there is 

not a frequency selection in LORAN-C. The most advanced 

units automatically select the optimum chain for navigation. 

Other units rely upon the pilot to select the appropriate chain 

with a manual entry.

After the LORAN-C receiver has been turned on, the unit 

must be initialized before it can be used for navigation. While 

this can be accomplished in flight, it is preferable to perform 

this task, which can take several minutes, on the ground. 

The methods for initialization are as varied as the number 

of different models of receivers. Some require pilot input 

during the process, such as verification or acknowledgment 

of the information displayed. 

Most units contain databases of navigational information. 

Frequently, such databases contain not only airport and 

NAVAID locations, but also extensive airport, airspace, and 

ATC information. While the unit can operate with an expired 

database, the information should be current or verified to be 

correct prior to use. The pilot can update some databases, 

while others require removal from the aircraft and the services 

of an avionics technician.

VFR navigation with LORAN-C can be as simple as telling 

the unit where the pilot wishes to go. The course guidance 

provided is a great circle (shortest distance) route to the 

destination. Older units may need a destination entered in 

terms of latitude and longitude, but recent designs need only 

the identifier of the airport or NAVAID. The unit also permits 

database storage and retrieval of pilot defined waypoints. 

LORAN-C signals follow the curvature of the Earth and are 

generally usable hundreds of miles from their transmitters. 

The LORAN-C signal is subject to degradation from a 

variety of atmospheric disturbances. It is also susceptible to 

interference from static electricity buildup on the airframe 

and electrically “noisy” airframe equipment. Flight in 

precipitation or even dust clouds can cause occasional 

interference with navigational guidance from LORAN-C 

signals. To minimize these effects, static wicks and bonding 

straps should be installed and properly maintained.

LORAN-C navigation information is presented to the pilot in 

a variety of ways. All units have self-contained displays, and 

some elaborate units feature built-in moving map displays. 

Some installations can also drive an external moving map 

display, a conventional VOR indicator, or a horizontal 

situation indicator (HSI). Course deviation information is 

presented as a linear deviation from course—there is no 

increase in tracking sensitivity as the aircraft approaches 

the waypoint or destination. Pilots must carefully observe 

placards, selector switch positions, and annunciator 

indications when utilizing LORAN-C because aircraft 

installations can vary widely. The pilot’s familiarity with 

unit operation through AFM/POH supplements and operating 

guides cannot be overemphasized. 

LORAN-C Notices to Airmen (NOTAMs) should be 

reviewed prior to relying on LORAN-C for navigation. 

LORAN-C NOTAMs are issued to announce outages for 

specific chains and transmitters. Pilots may obtain LORAN-C 

NOTAMs from FSS briefers only upon request.
15-32

The prudent pilot never relies solely on one means of 

navigation when others are available for backup and crosscheck. Pilots should never become so dependent upon the 

extensive capabilities of LORAN-C that other methods of 

navigation are neglected.

Global Positioning System

The GPS is a satellite-based radio navigation system. Its 

RNAV guidance is worldwide in scope. There are no symbols 

for GPS on aeronautical charts as it is a space-based system 

with global coverage. Development of the system is underway 

so that GPS is capable of providing the primary means of 

electronic navigation. Portable and yoke mounted units are 

proving to be very popular in addition to those permanently 

installed in the aircraft. Extensive navigation databases are 

common features in aircraft GPS receivers.

The GPS is a satellite radio navigation and time dissemination 

system developed and operated by the U.S. Department of 

Defense (DOD). Civilian interface and GPS system status 

is available from the U.S. Coast Guard.

It is not necessary to understand the technical aspects of 

GPS operation to use it in VFR/instrument flight rules (IFR) 

navigation. It does differ significantly from conventional, 

ground-based electronic navigation, and awareness of those 

differences is important. Awareness of equipment approvals 

and limitations is critical to the safety of flight. 

The GPS navigation system broadcasts a signal that is used 

by receivers to determine precise position anywhere in the 

world. The receiver tracks multiple satellites and determines 

a pseudorange measurement to determine the user location. 

A minimum of four satellites is necessary to establish an 

accurate three-dimensional position. The Department of 

Defense (DOD) is responsible for operating the GPS satellite 

constellation and monitors the GPS satellites to ensure proper 

operation.

The status of a GPS satellite is broadcast as part of the data 

message transmitted by the satellite. GPS status information 

is also available by means of the U.S. Coast Guard navigation 

information service at (703) 313-5907 or online at http://

www.navcen.uscg.gov/. Additionally, satellite status is 

available through the Notice to Airmen (NOTAM) system. 

The GPS receiver verifies the integrity (usability) of the 

signals received from the GPS constellation through receiver 

autonomous integrity monitoring (RAIM) to determine if 

a satellite is providing corrupted information. At least one 

satellite, in addition to those required for navigation, must be 

in view for the receiver to perform the RAIM function; thus, 

RAIM needs a minimum of five satellites in view, or four 

satellites and a barometric altimeter (baro-aiding) to detect an 

integrity anomaly. For receivers capable of doing so, RAIM 

needs six satellites in view (or five satellites with baro-aiding) 

to isolate the corrupt satellite signal and remove it from the 

navigation solution. Baro-aiding is a method of augmenting 

the GPS integrity solution by using a nonsatellite input 

source. GPS derived altitude should not be relied upon to 

determine aircraft altitude since the vertical error can be quite 

large and no integrity is provided. To ensure that baro-aiding 

is available, the current altimeter setting must be entered into 

the receiver as described in the operating manual. 

RAIM messages vary somewhat between receivers; however, 

generally there are two types. One type indicates that there 

are not enough satellites available to provide RAIM integrity 

monitoring and another type indicates that the RAIM integrity 

monitor has detected a potential error that exceeds the limit 

for the current phase of flight. Without RAIM capability, the 

pilot has no assurance of the accuracy of the GPS position. 

Selective Availability

Selective Availability (SA) is a method by which the accuracy 

of GPS is intentionally degraded. This feature is designed 

to deny hostile use of precise GPS positioning data. SA was 

discontinued on May 1, 2000, but many GPS receivers are 

designed to assume that SA is still active.

The GPS constellation of 24 satellites is designed so that a 

minimum of five satellites are always observable by a user 

anywhere on earth. The receiver uses data from a minimum of 

four satellites above the mask angle (the lowest angle above 

the horizon at which a receiver can use a satellite). 

VFR Use of GPS 

GPS navigation has become a great asset to VFR pilots, 

providing increased navigation capability and enhanced 

situational awareness, while reducing operating costs due 

to greater ease in flying direct routes. While GPS has many 

benefits to the VFR pilot, care must be exercised to ensure 

that system capabilities are not exceeded.

Types of receivers used for GPS navigation under VFR are 

varied, from a full IFR installation being used to support a 

VFR flight, to a VFR only installation (in either a VFR or IFR 

capable aircraft) to a hand-held receiver. The limitations of 

each type of receiver installation or use must be understood 

by the pilot to avoid misusing navigation information. In all 

cases, VFR pilots should never rely solely on one system 

of navigation. GPS navigation must be integrated with 

other forms of electronic navigation as well as pilotage 

and dead reckoning. Only through the integration of these 

techniques can the VFR pilot ensure accuracy in navigation. 
15-33

Some critical concerns in VFR use of GPS include RAIM 

capability, database currency and antenna location. 

RAIM Capability

Many VFR GPS receivers and all hand-held units have no 

RAIM alerting capability. Loss of the required number of 

satellites in view, or the detection of a position error, cannot 

be displayed to the pilot by such receivers. In receivers 

with no RAIM capability, no alert would be provided to the 

pilot that the navigation solution had deteriorated, and an 

undetected navigation error could occur. A systematic crosscheck with other navigation techniques would identify this 

failure, and prevent a serious deviation. 

In many receivers, an up-datable database is used for 

navigation fixes, airports, and instrument procedures. 

These databases must be maintained to the current update 

for IFR operation, but no such requirement exists for VFR 

use. However, in many cases, the database drives a moving 

map display which indicates Special Use Airspace and the 

various classes of airspace, in addition to other operational 

information. Without a current database the moving map 

display may be outdated and offer erroneous information to 

VFR pilots wishing to fly around critical airspace areas, such 

as a Restricted Area or a Class B airspace segment. Numerous 

pilots have ventured into airspace they were trying to avoid 

by using an outdated database. If there is not a current data 

base in the receiver, disregard the moving map display when 

making critical navigation decisions.

In addition, waypoints are added, removed, relocated, or renamed as required to meet operational needs. When using 

GPS to navigate relative to a named fix, a current database 

must be used to properly locate a named waypoint. Without 

the update, it is the pilot’s responsibility to verify the 

waypoint location referencing to an official current source, 

such as the A/FD, sectional chart, or en route chart. 

In many VFR installations of GPS receivers, antenna location 

is more a matter of convenience than performance. In IFR 

installations, care is exercised to ensure that an adequate 

clear view is provided for the antenna to see satellites. If an 

alternate location is used, some portion of the aircraft may 

block the view of the antenna, causing a greater opportunity 

to lose navigation signal. 

This is especially true in the case of hand-helds. The use of 

hand-held receivers for VFR operations is a growing trend, 

especially among rental pilots. Typically, suction cups are 

used to place the GPS antennas on the inside of aircraft 

windows. While this method has great utility, the antenna 

location is limited by aircraft structure for optimal reception 

of available satellites. Consequently, signal losses may occur 

in certain situations of aircraft-satellite geometry, causing a 

loss of navigation signal. These losses, coupled with a lack 

of RAIM capability, could present erroneous position and 

navigation information with no warning to the pilot. 

While the use of a hand-held GPS for VFR operations is not 

limited by regulation, modification of the aircraft, such as 

installing a panel- or yoke-mounted holder, is governed by 14 

CFR part 43. Pilots should consult with a mechanic to ensure 

compliance with the regulation and a safe installation. 

Tips for Using GPS for VFR Operations

Always check to see if the unit has RAIM capability. If no 

RAIM capability exists, be suspicious of a GPS displayed 

position when any disagreement exists with the position 

derived from other radio navigation systems, pilotage, or 

dead reckoning. 

Check the currency of the database, if any. If expired, update 

the database using the current revision. If an update of an 

expired database is not possible, disregard any moving map 

display of airspace for critical navigation decisions. Be aware 

that named waypoints may no longer exist or may have 

been relocated since the database expired. At a minimum, 

the waypoints planned to be used should be checked against 

a current official source, such as the A/FD, or a Sectional 

Aeronautical Chart. 

While a hand-held GPS receiver can provide excellent 

navigation capability to VFR pilots, be prepared for 

intermittent loss of navigation signal, possibly with no RAIM 

warning to the pilot. If mounting the receiver in the aircraft, 

be sure to comply with 14 CFR part 43. 

Plan flights carefully before taking off. If navigating to userdefined waypoints, enter them before flight, not on the fly. 

Verify the planned flight against a current source, such as a 

current sectional chart. There have been cases in which one 

pilot used waypoints created by another pilot that were not 

where the pilot flying was expecting. This generally resulted 

in a navigation error. Minimize head-down time in the aircraft 

and keep a sharp lookout for traffic, terrain, and obstacles. 

Just a few minutes of preparation and planning on the ground 

makes a great difference in the air. 

Another way to minimize head-down time is to become very 

familiar with the receiver’s operation. Most receivers are not 

intuitive. The pilot must take the time to learn the various 

keystrokes, knob functions, and displays that are used in 

the operation of the receiver. Some manufacturers provide 

computer-based tutorials or simulations of their receivers. 

Take the time to learn about the particular unit before using 

it in flight. 
15-34

In summary, be careful not to rely on GPS to solve all VFR 

navigational problems. Unless an IFR receiver is installed in 

accordance with IFR requirements, no standard of accuracy 

or integrity has been assured. While the practicality of 

GPS is compelling, the fact remains that only the pilot can 

navigate the aircraft, and GPS is just one of the pilot’s tools 

to do the job. 

VFR Waypoints 

VFR waypoints provide VFR pilots with a supplementary 

tool to assist with position awareness while navigating 

visually in aircraft equipped with area navigation receivers. 

VFR waypoints should be used as a tool to supplement current 

navigation procedures. The uses of VFR waypoints include 

providing navigational aids for pilots unfamiliar with an area, 

waypoint definition of existing reporting points, enhanced 

navigation in and around Class B and Class C airspace, and 

enhanced navigation around Special Use Airspace. VFR 

pilots should rely on appropriate and current aeronautical 

charts published specifically for visual navigation. If 

operating in a terminal area, pilots should take advantage of 

the Terminal Area Chart available for that area, if published. 

The use of VFR waypoints does not relieve the pilot of any 

responsibility to comply with the operational requirements 

of 14 CFR part 91. 

VFR waypoint names (for computer entry and flight plans) 

consist of five letters beginning with the letters “VP” 

and are retrievable from navigation databases. The VFR 

waypoint names are not intended to be pronounceable, 

and they are not for use in ATC communications. On VFR 

charts, a stand-alone VFR waypoint is portrayed using the 

same four-point star symbol used for IFR waypoints. VFR 

waypoint collocated with a visual checkpoint on the chart is 

identified by a small magenta flag symbol. A VFR waypoint 

collocated with a visual checkpoint is pronounceable based 

on the name of the visual checkpoint and may be used for 

ATC communications. Each VFR waypoint name appears in 

parentheses adjacent to the geographic location on the chart. 

Latitude/longitude data for all established VFR waypoints 

may be found in the appropriate regional A/FD. 

When filing VFR flight plans, use the five-letter identifier as 

a waypoint in the route of flight section if there is an intended 

course change at that point or if used to describe the planned 

route of flight. This VFR filing would be similar to VOR use 

in a route of flight. Pilots must use the VFR waypoints only 

when operating under VFR conditions. 

Any VFR waypoints intended for use during a flight should 

be loaded into the receiver while on the ground and prior to 

departure. Once airborne, pilots should avoid programming 

routes or VFR waypoint chains into their receivers. 

Pilots should be especially vigilant for other traffic while 

operating near VFR waypoints. The same effort to see 

and avoid other aircraft near VFR waypoints is necessary, 

as is the case when operating near VORs and NDBs. In 

fact, the increased accuracy of navigation through the use 

of GPS demands even greater vigilance, as off-course 

deviations among different pilots and receivers is less. 

When operating near a VFR waypoint, use whatever ATC 

services are available, even if outside a class of airspace 

where communications are required. Regardless of the class 

of airspace, monitor the available ATC frequency closely for 

information on other aircraft operating in the vicinity. It is 

also a good idea to turn on landing light(s) when operating 

near a VFR waypoint to make the aircraft more conspicuous 

to other pilots, especially when visibility is reduced. 

Lost Procedures

Getting lost in an aircraft is a potentially dangerous situation 

especially when low on fuel. If a pilot becomes lost, there 

are some good common sense procedures to follow. If a 

town or city cannot be seen, the first thing to do is climb, 

being mindful of traffic and weather conditions. An increase 

in altitude increases radio and navigation reception range, 

and also increases radar coverage. If flying near a town or 

city, it might be possible to read the name of the town on a 

water tower.

If the aircraft has a navigational radio, such as a VOR or ADF 

receiver, it can be possible to determine position by plotting 

an azimuth from two or more navigational facilities. If GPS 

is installed, or a pilot has a portable aviation GPS on board, 

it can be used to determine the position and the location of 

the nearest airport.

Communicate with any available facility using frequencies 

shown on the sectional chart. If contact is made with a 

controller, radar vectors may be offered. Other facilities may 

offer direction finding (DF) assistance. To use this procedure, 

the controller requests the pilot to hold down the transmit 

button for a few seconds and then release it. The controller 

may ask the pilot to change directions a few times and repeat 

the transmit procedure. This gives the controller enough 

information to plot the aircraft position and then give vectors 

to a suitable landing site. If the situation becomes threatening, 

transmit the situation on the emergency frequency 121.5 MHz 

and set the transponder to 7700. Most facilities, and even 

airliners, monitor the emergency frequency.

Flight Diversion

There probably comes a time when a pilot is not able to 

make it to the planned destination. This can be the result of 

unpredicted weather conditions, a system malfunction, or 
15-35

poor preflight planning. In any case, the pilot needs to be 

able to safely and efficiently divert to an alternate destination. 

Before any cross-country flight, check the charts for airports 

or suitable landing areas along or near the route of flight. 

Also, check for navigational aids that can be used during a 

diversion.

Computing course, time, speed, and distance information in 

flight requires the same computations used during preflight 

planning. However, because of the limited flight deck space, 

and because attention must be divided between flying the 

aircraft, making calculations, and scanning for other aircraft, 

take advantage of all possible shortcuts and rule-of-thumb 

computations.

When in flight, it is rarely practical to actually plot a course 

on a sectional chart and mark checkpoints and distances. 

Furthermore, because an alternate airport is usually not 

very far from your original course, actual plotting is seldom 

necessary.

A course to an alternate can be measured accurately with a 

protractor or plotter, but can also be measured with reasonable 

accuracy using a straightedge and the compass rose depicted 

around VOR stations. This approximation can be made on the 

basis of a radial from a nearby VOR or an airway that closely 

parallels the course to your alternate. However, remember 

that the magnetic heading associated with a VOR radial 

or printed airway is outbound from the station. To find the 

course TO the station, it may be necessary to determine the 

reciprocal of that heading. It is typically easier to navigate 

to an alternate airport that has a VOR or NDB facility on 

the field.

After selecting the most appropriate alternate, approximate 

the magnetic course to the alternate using a compass rose 

or airway on the sectional chart. If time permits, try to start 

the diversion over a prominent ground feature. However, 

in an emergency, divert promptly toward your alternate. 

Attempting to complete all plotting, measuring, and 

computations involved before diverting to the alternate may 

only aggravate an actual emergency.

Once established on course, note the time, and then use the 

winds aloft nearest to your diversion point to calculate a 

heading and GS. Once a GS has been calculated, determine 

a new arrival time and fuel consumption. Give priority to 

flying the aircraft while dividing attention between navigation 

and planning. When determining an altitude to use while 

diverting, consider cloud heights, winds, terrain, and radio 

reception.

Chapter Summary

This chapter has discussed the fundamentals of VFR 

navigation. Beginning with an introduction to the charts that 

can be used for navigation to the more technically advanced 

concept of GPS, there is one aspect of navigation that remains 

the same. The pilot is responsible for proper planning and the 

execution of that planning to ensure a safe flight. 
15-36