General Navigation

General navigation answers three questions on every flight: where am I, where am I going, and how long will it take? GPS answers them for you most of the time, but a pilot who understands the basics can plan a flight, check the computer's work and keep going when the screen goes blank.

1. The Earth and its grid

The Earth is almost a sphere, very slightly flattened at the poles. To give every point an address we use a grid:

• Latitude: the angle north or south of the equator, from 0° to 90° N or S. Lines of latitude are called parallels.
• Longitude: the angle east or west of the prime meridian through Greenwich, from 0° to 180° E or W. Lines of longitude are called meridians and they all meet at the poles.
• Each degree is split into 60 minutes (′). Amman Queen Alia (OJAI) is at about 31°43′N 035°59′E.

Distance from the grid

• Along a meridian, 1 minute of latitude = 1 nautical mile, so 1° of latitude = 60 NM anywhere on Earth.
• Along a parallel, meridians get closer together towards the poles. The distance is called departure: departure (NM) = change of longitude (minutes) × cos(latitude). At the equator 1° of longitude is 60 NM; at 32°N (Amman) it is about 51 NM; at 60°N only 30 NM.

2. Units

Unit	Value	Used for
Nautical mile (NM)	1,852 m	Distances in the air
Knot (kt)	1 NM per hour	Speeds and wind
Statute mile (SM)	1,609 m	Visibility in North America
Foot (ft)	0.3048 m (1 m ≈ 3.28 ft)	Altitude and elevation

Quick conversions: NM × 1.85 = km, km × 0.54 = NM, metres × 3.3 ≈ feet.

3. Direction: true, magnetic and compass

• True north is the direction of the geographic North Pole. Charts are drawn to true north.
• Magnetic north is where a compass points. The angle between them is the variation, printed on charts as lines called isogonals. In the Levant variation is small and easterly, about 4°–6° E.
• The aircraft's own metal and electrics bend the compass a little more: that error is the deviation, written on the deviation card next to the compass.

To go from true to magnetic: "Variation east, magnetic least; variation west, magnetic best." With 5° E variation, a true track of 090° is a magnetic track of 085°. The full chain is True → (variation) → Magnetic → (deviation) → Compass.

Runways, ATC headings and the semicircular cruising levels all use magnetic directions.

4. Great circles and rhumb lines

• A great circle is any circle whose centre is the centre of the Earth (the equator and every meridian are great circles). The shortest route between two points is the arc of the great circle through them, but its direction keeps changing along the way.
• A rhumb line crosses every meridian at the same angle, so you can fly it on one constant track. It is slightly longer than the great circle, except along the equator or a meridian.
• On short flights the difference is tiny; on long-haul flights airliners follow the great circle (Amman to Toronto passes over Europe and the North Atlantic, not straight west).

5. Charts

• The scale compares chart distance to real distance. On a 1:500,000 chart (the usual VFR chart), 1 cm on the chart is 5 km on the ground.
• Lambert conformal conic: the projection of most aviation charts. A straight line is very close to a great circle and the scale is almost constant over the chart.
• Mercator: a straight line is a rhumb line, but distances grow towards the poles (that is why Greenland looks huge on world maps).
• Measure tracks from the meridian nearest the middle of your route, because meridians are not parallel on a Lambert chart.

6. Time

• Aviation uses UTC (Coordinated Universal Time, "Zulu") everywhere: flight plans, METARs, NOTAMs and ATC.
• The Earth turns 360° in 24 hours: 15° of longitude = 1 hour, so 1° = 4 minutes.
• Jordan, Syria, Iraq and Saudi Arabia keep UTC+3 all year; Lebanon is UTC+2 in winter and UTC+3 in summer. Always convert to UTC before planning.

7. Speeds

Speed	What it is
IAS – indicated airspeed	What the airspeed indicator shows; used for flying the aircraft (stall, flap and gear limits).
CAS – calibrated airspeed	IAS corrected for instrument and position errors.
TAS – true airspeed	The real speed through the air. Thinner air at altitude makes TAS higher than IAS: roughly +2% per 1,000 ft.
GS – ground speed	Speed over the ground: TAS plus or minus the wind. This is what decides your flight time.

Example: 120 kt IAS at 6,000 ft is about 134 kt TAS (120 + 12%).

8. The wind triangle

The aircraft moves through the air while the air itself moves over the ground. Three vectors make a triangle:

• Heading and TAS: where the nose points and how fast the aircraft moves through the air.
• Wind direction and speed: always given as the direction the wind blows from.
• Track and ground speed: the actual path and speed over the ground.

The angle between heading and track is the drift. To fly a chosen track you turn the nose into the wind by the wind correction angle.

Mental rules of thumb

• Maximum drift (wind straight across) ≈ wind speed × 60 ÷ TAS. A 20 kt crosswind at 120 kt TAS gives up to 10° of drift.
• For a wind at an angle: 30° off the nose gives about half of the maximum, 45° about 70% and 60° about 90%.
• Headwind component: wind 30° off the nose costs about 85% of its speed as headwind, 60° off about 50%.

Worked example: you want a track of 360°, TAS 120 kt, wind 090°/20 kt (from the right). Maximum drift is 20 × 60 ÷ 120 = 10°, so steer about 010° into the wind. The wind is almost straight across, so ground speed stays close to 120 kt.

9. The 1-in-60 rule

At 60 NM from a point, 1° of angle is about 1 NM sideways. It makes off-track corrections easy:

1. Track error = distance off track × 60 ÷ distance flown. 3 NM off after 30 NM flown = 6° error.
2. Closing angle = distance off track × 60 ÷ distance to go. With 60 NM still to go, 3 NM off = 3°.
3. To reach the destination, turn by track error + closing angle: 6° + 3° = 9° towards the planned track.

10. Time, speed, distance and fuel

Everything follows from distance = speed × time:

• Time (minutes) = distance ÷ ground speed × 60. 90 NM at 120 kt GS = 45 minutes.
• A quick trick: at 120 kt you cover 2 NM per minute; at 180 kt, 3 NM per minute; at 240 kt, 4 NM per minute.
• Fuel = burn per hour × time. A 45-minute leg at 30 litres/hour uses 22.5 litres, plus your reserve.

11. Dead reckoning in practice

1. Plan: draw the track, measure it (true, then magnetic), note distances and pick checkpoints every 10–15 minutes, easy to see from the air (lakes, motorways, towns, coastlines).
2. Calculate heading and ground speed with the forecast wind, then the time and ETA for each leg.
3. Fly the heading, note the time over each checkpoint and compare it with the plan.
4. Correct: off track? Use the 1-in-60 rule. Early or late? Work out the real ground speed and revise the ETA.

Flying it at Levant

SimBrief and the flight management computer solve the wind triangle for you, but the numbers on the OFP use exactly these ideas: magnetic tracks, TAS and ground speed, the winds aloft and time and fuel per leg. Compare the OFP's times with your progress in flight, and try a short VFR hop – Amman to Aqaba along the Desert Highway – with only a chart, a clock and the 1-in-60 rule.

Check yourself

1. How many nautical miles is 1° of latitude? 60 NM.
2. True track 180°, variation 5° E. What is the magnetic track? 175° (east is least).
3. TAS 150 kt, crosswind 25 kt. What is the maximum drift? 25 × 60 ÷ 150 = 10°.
4. After 40 NM you are 2 NM left of track, with 80 NM to go. How much do you turn? Track error 3° + closing angle 1.5° ≈ 4.5° to the right.
5. 120 NM at a ground speed of 160 kt: how long? 45 minutes.
6. The time is 14:30 local in Amman. What is it in UTC? 11:30 UTC (Jordan is UTC+3).

This lesson is simulation training material based on standard PPL navigation theory. Variation values and time zones change: always use current charts and publications.