What is the difference between a great circle and a rhumb line?

A great circle is the shortest distance between two points on the surface of the Earth. Great circle tracks constantly change direction as they cross successive meridians, curving toward the poles. A rhumb line crosses all meridians at the same angle and maintains a constant track direction. On a Mercator chart, rhumb lines appear as straight lines, but they are longer than the great circle route (except at the equator).

What are the properties of Mercator, Lambert Conformal and Polar Stereographic chart projections?

Mercator: rhumb lines are straight, great circles are curves, conformal, scale expands with latitude. Used for equatorial regions. Lambert Conformal Conic: great circles are approximately straight lines — the key navigation advantage, conformal, two standard parallels, used for mid-latitude en-route charts. Polar Stereographic: used for polar regions above 78N/S, great circles approximately straight, meridians are straight lines from the pole.

How do you solve triangle of velocities problems?

The triangle of velocities relates three vectors: Heading/TAS (aircraft direction through air), Wind velocity, and Track/Ground Speed (actual path over ground). Track/GS = Heading/TAS + Wind. Drift angle is the difference between heading and track.

What is dead reckoning navigation?

Dead reckoning (DR) is estimating current position from a known starting position using heading, speed, elapsed time and wind correction. DR accuracy degrades over time as wind estimation errors accumulate. The 1 in 60 rule states a 1 degree track error produces 1 nm off-track per 60 nm flown.

ATPL Theory — General Navigation

Master General Navigation for your ATPL theory exam

Free practice questions covering great circles, chart projections, triangle of velocities, variation and deviation, CRP-5, dead reckoning, time calculations and position fixing — with detailed explanations for every answer.

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10 Topic areas

75% EASA pass mark

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Questions

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Syllabus Coverage

Topics covered in this question bank

All major General Navigation topic areas from the EASA ATPL syllabus, from Earth geometry through to operational navigation planning.

⊙The Earth & Great Circles

⊙Chart Projections

⊙Distance & Direction

⊙Variation & Deviation

⊙Speed — TAS, IAS, GS, Mach

⊙Triangle of Velocities

⊙Dead Reckoning

⊙CRP-5 Navigation Computer

⊙Time — UTC, LMT, Standard

⊙Position Fixing

Key Reference — Chart Projections

Mercator, Lambert and Polar Stereographic — properties compared

Chart projection properties are directly tested and must be memorised precisely. The key exam question is always which chart shows great circles as straight lines.

Projection	Rhumb Lines	Great Circles	Primary Use
Mercator	Straight lines ✓	Curved (except equator & meridians)	Equatorial regions, plotting rhumb tracks
Lambert Conformal	Curved	Approximately straight ✓	Mid-latitude en-route charts (most used)
Polar Stereographic	Curved	Approximately straight ✓	Polar regions above 78°N/S

True → Magnetic → Compass Conversion

True ± Variation = Magnetic ± Deviation = Compass CADET mnemonic: Compass ADd East variation for True. Variation W = subtract from True to get Magnetic. Variation E = add.

EASA Exam Format

What to expect on the real exam

General Navigation contains a high proportion of calculation questions — triangle of velocities, time conversions, distance/speed/time problems and drift/heading problems on the CRP-5. Many questions give you a diagram or scenario and require you to extract values and calculate. Practise with actual numbers, not just theory.

~60

Questions in exam

75%

Pass mark required

120 min

Exam duration

About This Subject

Why General Navigation is a core ATPL skill

Navigation underpins all flying. Understanding how to determine position, plan tracks, account for wind, convert between direction types, and interpret charts is fundamental to safe flight operations worldwide. General Navigation builds the conceptual foundation that Radio Navigation and Flight Planning build upon.

Questions are aligned with the EASA ATPL syllabus and cover the complete range from Earth geometry and chart theory through to operational dead reckoning, time zone calculations and the practical use of navigation computers.

Sample Question

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General Navigation — Sample Question

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