RPL Exam Navigation: Charts, Compass, and Track Calculations for the CASA Test

Navigation questions in the RPL exam test your ability to read aviation charts, understand compass errors, and do basic track and heading calculations. The good news: the calculations are simple once you understand the underlying concepts. This guide covers everything CASA tests.

Aviation charts used in Australia

Two chart types are tested in the RPL exam. Understanding the scale and purpose of each will help you answer chart-reading questions quickly and accurately.

Visual Navigation Chart (VNC) — 1:500,000 scale

The Visual Navigation Chart (VNC) is used for short-distance navigation within a region. At a scale of 1:500,000, every centimetre on the chart equals 5 km on the ground. VNCs are published in folded sections covering major flying areas across Australia.

World Aeronautical Chart (WAC) — 1:1,000,000 scale

The World Aeronautical Chart (WAC) is used for longer cross-country navigation. At a scale of 1:1,000,000, every centimetre equals 10 km on the ground, allowing larger areas to be covered on a single chart.

Chart features to know

Both the VNC and WAC share common features that appear in exam questions. You should be able to identify and interpret each of the following:

• Contours — lines of equal elevation; the closer together they are, the steeper the terrain.
• Spot heights — specific peak elevations marked at a point on the chart.
• Aerodrome symbols — different symbols are used for certified aerodromes, aerodromes with control towers, water aerodromes, and helicopter landing areas.
• Airspace boundaries — marked with different colours and patterns for each airspace class.
• Isogonals — lines of equal magnetic variation, also called isogonic lines.
• Obstacles — towers, pylons, and other obstructions with heights given in feet AMSL and AGL.

Latitude and longitude

Positions on Earth are defined by latitude (north/south from the equator) and longitude (east/west from Greenwich). In Australia, latitude ranges from approximately 10°S to 44°S, and longitude from approximately 113°E to 154°E.

One degree of latitude equals approximately 60 nm (nautical miles), and one minute of latitude equals 1 nm. This relationship applies precisely to latitude only — the equivalent distance for longitude varies with latitude.

Magnetic variation

A compass points to Magnetic North, not True North. The difference between them is called magnetic variation, which changes with geographic location and also changes slowly over time. Australia has easterly variation across most of the country, meaning magnetic north lies to the east of true north.

Variation conversion formula

The CADET rule is the standard memory aid: Compass Add East to get True, or True Subtract East to get Compass (westerly variation is the opposite). Put more simply: True + West = Magnetic and True − East = Magnetic when converting a true heading to a magnetic heading.

Example: True heading = 270°, magnetic variation = 10°E → Magnetic heading = 270° − 10° = 260°. This is frequently tested in the CASA exam.

Compass deviation

Even after correcting for magnetic variation, a compass may have deviation — small errors caused by magnetic fields from the aircraft's own metal structure and electrical systems. Deviation varies depending on the heading being flown and is recorded on a compass deviation card kept in the cockpit.

The full correction sequence is: True → apply variation → Magnetic → apply deviation → Compass. Exam trap: don't confuse variation (a geographic property) with deviation (an aircraft-specific property).

Track vs heading

These two terms are frequently confused in exam questions, so it is important to understand the distinction clearly.

• Track (also called "track made good"): the actual path of the aircraft over the ground — the line drawn on the chart.
• Heading: the direction the aircraft's nose is pointed — this may differ from track due to wind.

In still air (no wind), heading equals track. In a crosswind, the pilot must angle into the wind, so heading does not equal track. The required heading to achieve a given track is called the heading to fly.

Wind effect and Wind Correction Angle (WCA)

Wind pushes the aircraft sideways, causing it to drift off the planned track. To compensate, the pilot applies a Wind Correction Angle (WCA) — pointing the nose into the wind by an amount that exactly cancels the drift.

Calculating WCA (approximation)

The exact calculation uses the wind triangle, but for the RPL exam a simplified formula is sufficient:

WCA ≈ (crosswind component ÷ TAS) × 60

Where the crosswind component equals wind speed × sin(angle between wind and track). For example: a crosswind of 20 kt perpendicular to the track with a TAS of 90 kt gives a WCA of (20 ÷ 90) × 60 = approximately 13°. The pilot points the nose 13° into the wind to maintain the planned track.

Groundspeed

Groundspeed is your actual speed over the ground, and it is affected by the headwind and tailwind components of the wind:

• A headwind reduces groundspeed: GS = TAS − headwind component.
• A tailwind increases groundspeed: GS = TAS + tailwind component.
• A pure crosswind has minimal effect on groundspeed (a slight reduction only).

Groundspeed affects your Estimated Time of Arrival (ETA) — a headwind means a longer flight time, while a tailwind means an earlier arrival.

Time and distance calculations

The core formula is: Distance = Speed × Time. Rearranged as needed:

• Time = Distance ÷ Groundspeed
• Distance = Groundspeed × Time

The CASA exam uses round numbers, so mental arithmetic is usually sufficient. For example: if groundspeed = 120 kt and distance = 30 nm, then time = 15 minutes. Practise these calculations until they feel automatic.

Fuel calculations

Fuel planning uses fuel flow (litres per hour) and flight time to determine the fuel required for a trip:

Fuel required = Fuel flow × Time + Reserve

The required reserve for day VFR is 45 minutes at cruise power. For example: a trip of 2 hours at a fuel flow of 25 L/hr requires 50 L for the trip plus 18.75 L for the reserve, giving approximately 69 L minimum. Always add a practical margin above this minimum.

Compass errors

The magnetic compass has two turning and acceleration errors that CASA tests in the RPL exam. Both are caused by the dip component of the Earth's magnetic field, which is more pronounced in the Southern Hemisphere.

Northerly Turning Error (NTE)

When turning through north in the Southern Hemisphere, the compass initially indicates a turn in the correct direction but then lags and may indicate a turn in the opposite direction. The compass "hunts" near north headings due to the dip component of the Earth's magnetic field. Exam trap: don't stop the turn too early or too late when rolling out on a northerly heading.

Acceleration error

On easterly or westerly headings, the compass indicates a heading change when the aircraft accelerates or decelerates. The mnemonic ANDS summarises the effect in the Southern Hemisphere: Accelerate North, Decelerate South (on east/west headings). For example, accelerating on an easterly heading will cause the compass to show an apparent turn towards north.

Track Error (TE) and regaining track

After departure, if the wind differs from what was planned or the heading is slightly off, the aircraft will drift from the planned track. The angle between the planned track and the actual track flown is called the Track Error (TE).

To regain the planned track, apply double the track error angle back towards the planned track. Once established on track, reduce back to the original heading (adjusted for wind correction) to maintain it.

Common navigation exam traps

The following points summarise the most common mistakes students make on navigation questions in the CASA RPL exam:

• Track is the path over the ground; heading is where the nose points — do not confuse them.
• In the Southern Hemisphere, magnetic variation is usually easterly — remember the CADET rule when converting.
• Compass deviation is small (usually less than 5°) and varies with heading — always check the deviation card.
• Northerly Turning Error causes the compass to lag when turning through north — account for this when rolling out on a northerly heading.
• Groundspeed, not TAS, determines your ETA and fuel burn over a route.

Putting it all together: practice navigation questions

Navigation questions in the RPL exam typically present a scenario — a heading, a wind, and a requirement to calculate drift, groundspeed, or ETA. Working through practice questions is the fastest way to build confidence with these calculations. See our navigation study guide for additional worked examples covering chart reading, wind correction, and compass errors in the same format as the real CASA test.

Related Resources

• Navigation Study Guide
• Crosswind Calculations Guide
• All RPL Exam Topics