General Navigation is one of the most calculation-heavy DGCA papers — which is exactly why examiners return to the same handful of ideas year after year. Get comfortable with these five, and a large share of the paper stops being a surprise.
This is the single most useful shortcut in air navigation. It states that 1° of track error equals roughly 1 nautical mile of off-track distance for every 60 nautical miles flown. In other words, if you're 2 NM off track after flying 60 NM, you've drifted about 2° off your intended heading.
DGCA loves this rule because it turns messy trigonometry into simple division. Practice the two common question types: (a) working out how far off-track you are given a heading error, and (b) working out the heading correction needed to regain track and also reach your destination — this second type combines a "regain track" correction with a "closing angle" correction, so don't stop halfway.
A Rhumb Line crosses every meridian at the same angle — it looks like a straight line on a Mercator chart, but it isn't the shortest path over the earth's curved surface. A Great Circle is the shortest distance between two points, but on a Mercator chart it appears as a curve bending toward the pole.
Key exam point: in the Northern Hemisphere, the Great Circle track is greater than the Rhumb Line track at the point of departure, and less than it at the destination. This is why long-haul flights fly a Great Circle route broken into a series of Rhumb Line legs — it's efficient to fly, but simple to plot.
PET is the point along a route where it takes exactly the same time to continue to the destination as it does to return to the departure point — factoring in wind. It answers "if something happens right now, is it faster to go on or turn back?"
PSR is the furthest point along the route from which the aircraft can still return to a suitable aerodrome with the required fuel reserves intact. It answers a fuel question, not a time question — don't mix the two formulas up. Most numerical mistakes here come from using ground speed instead of the correct out/home speeds, so always double-check which speed belongs in which half of the formula.
Chart scale is expressed as a ratio (e.g. 1:500,000) meaning 1 unit on the chart equals 500,000 of the same units on the ground. Convert carefully between nautical miles, statute miles and kilometres — DGCA numericals frequently disguise a straightforward scale question inside unit-conversion traps. Memorise: 1 NM = 1.15 statute miles = 1.852 km.
Every heading exists in three forms: True (relative to the geographic North Pole), Magnetic (relative to magnetic North, found by applying variation to True), and Compass (what the aircraft's compass actually shows, found by applying deviation to Magnetic). The conversion order matters: True → apply Variation → Magnetic → apply Deviation → Compass. Going the other direction, reverse both the order and the sign. A simple way to remember the sign convention: "variation west, magnetic best; variation east, magnetic least" — and the same rhyme applies to deviation and compass.
These five ideas — the 1-in-60 rule, Rhumb Line vs Great Circle, PET/PSR, scale conversions, and the True–Magnetic–Compass chain — cover a disproportionate share of General Navigation numericals. Drill each one until the formula is automatic, then move on to timed past-paper practice so you're applying them under exam pressure, not just in isolation.
Practice real DGCA-style Navigation questions and track your progress topic by topic.
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