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THE

PILOT

general
navigation
ATPL
STUDENT
pilot
resume

all info you need to pass atpl exams

GNAV

The solar system:
st
1 law Kepler: Planets move in elliptical orbits with the sun at one of the foci
nd
2 law Kepler: Radius vector sun-earth sweeps out equal areas in equal time
Sun’s declination:
Angle between earth’s equator & sun rays
Northerly: Daylight in S hemisphere shorter
Angular distance of the sun N/S of the celestial equator
Sun’s position relative to the plane of the Equator
Plane of ecliptic:
o
Plane of which the earth travels around the sun, the earth’s axis is 23
...
5 inclination with the ecliptic plane
Yearly apparent path of the SUN around the EARTH
Inclination is the main reason for occurrence of the seasons
Apparent sun: Visible sun, always in the plane of ecliptic
Mean sun: Fictitious sun coinciding each year at spring equinox & travelling along celestial equator at uniform/constant speed
Difference between mean sun & apparent sun highest in February & November
Midnight sun: Sun visible for 24 hours
Perihelion: Closest, beginning of January [Highest speed of earth’s orbit]
Aphelion: Furthest, beginning of July
o
Cancer/Capricorn: 23
...
5N/S
Equinoxes: Length of day/night & rate of change of declination of the sun highest
Spring: Declination = 0
Autumn: Declination = 0
Earth’s rotation: Viewed from above North Pole = Counter clockwise
Solstice: Summer/winter, point when sun reaches its highest/lowest declination
Sidereal day: Describe a relationship concerning the stars
Apparent solar day: Varies continuously due to tilt of Earth’s axis & elliptical orbit around the sun
Solar system doesn’t include stars
The earth:
1NM = 1
...
Diameter = 12700km
Circumference: 21600NM
Halfway between two points, GCT = RLT
Convergence of meridians: Angular difference between meridians
Convergence angle: Angular difference between RLT & GCT
Great circle track (Orthodrome, radio bearings)
Rhumb line closer to equator
GC run through area of higher latitude
GC shorter than RL
Small circle: Does not pass earth’s axis
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E
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E
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5deg) has the least effect on the amount of daylight with latitude
change
Directions:
NH
SH
PW
E
W
PE
W
E
First convert reference meridian to 000 prime meridian (Grid track + reference)
Convergency east true least, convergency west true best
True track increase NH, decreases SH
Grid convergence = Difference in direction between Grid North & True North
Grid convergence westerly: TN west of GN/for positions East of the grid datum meridian on NH
Grid convergence easterly: TN east of GN
Wind correction: R is (+) & L is (-)
True north: Direction of observer’s meridian to the North Pole, orientation of local meridian
o
Magnetic North moves 1 in 5 years
Earth is a magnet with the blue pole at the North Pole (North Canada) and direction of magnetic force straight down to earth’s
surface
Field direction is from magnet’s red pole to the magnet’s blue pole
Magnetic compass most effective midway between magnetic poles
Force acting on a needle of a DRC is directly proportional to horizontal component of the earth’s magnetic field
Total magnetic force strongest at the poles
Directive force: Resultant magnetic force in the horizontal plane in the position where the compass is installed
Increasing magnetic latitude = Increasing inclination & vertical component of the field
Horizontal component of the Earth’s magnetic field:
Maximum at magnetic equator
Very small at the poles
o
o
Approximately the same at 50 N & 50 S
Equals to total strength at magnetic equator
o

Magnetic variation is max at 180
Magnetic variation westerly is negative (-), easterly is positive (+)
Variation is east when MN is east of TN
Magnetic equator: Horizontal & total strength of magnetic field are the same
Magnetic meridian: Horizontal direction of the Earth’s magnetic field in that position, toward the magnetic north pole
Deviation changes because the undesired magnetic pole is moved relative to the direction of the earth’s magnetic field
Compass deviation is a force in direction perpendicular to the compass needle
Compass deviation applied to compass heading to get magnetic heading [Important]
Compass deviation affected by: Magnetic latitude, aircraft heading & aircraft electronic equipment
Compass deviation decrease as latitude decrease as horizontal component becomes stronger
Compass free from extraneous magnetic influence: Magnetic heading
Compass affected by extraneous magnetic influence: Compass heading
Compass needle marked red is north seeking pole
Compass needle will align itself with the direction of the magnetic lines of force
Purpose of GRID: Provide a system for directions where a great circle has a constant direction even if true direction varies
Grid lines are all parallel to the reference meridian

GRIVATION: Grid convergence + variation/ difference between GH & MH
Agonic line:
Follows separate paths out of the North Polar Regions, one running through Western Europe, & another through US
o
Positions that have 0 variation
Positions where magnetic & true meridians are parallel
Isogonals:
Lines of equal magnetic variation
Converge at N & S geographic & magnetic poles
Isoclinals: Lines of equal magnetic dip
Aclinic: Line of zero magnetic dip
Isogrives: Lines of equal grivation
Strength of horizontal component: Tesla x cos (dip)
-1
Dip angle = cos (H/T)
Magnetic track angle: Direction of a line referenced to Magnetic North
Distances:
1NM = 1
...
28ft
1 inch = 2
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54cm
General:
Aeronautical charts: Exact scale vary within the chart
“Scale”: The ratio of chart length compared to the Earth’s distance that it represents
Mercator chart:
Scale varies with 1/cosine latitude (secant)
Expands with secant of latitude
Based on a cylindrical projection
It’s a cylindrical projection but it is in fact mathematically produced
o
Convergency is 0
Not possible to represent N/S poles
Scale increases with increasing distance from the equator
Chart convergence = earth convergence at equator
Lamberts:
Chart convergence is constant & does not change with latitude
Chart convergence d

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