VFR Navigation Log

VFR Navigation Log glossary

Key terms behind the nav log's fields and computed columns.

Leg

A single segment of your route between two consecutive checkpoints, planned and flown as one unit, and the nav log computes heading, time, and fuel one leg at a time so small errors stay contained instead of compounding across the whole flight.

Checkpoint (Fix)

An identifiable landmark or defined position (a town, lake, VOR, or intersection) that marks the start or end of a leg, used to confirm you are on course and on time.

Nautical Mile (NM)

The standard aviation unit of distance, equal to one minute of latitude (about 1.15 statute miles or 6,076 feet), and leg distances are measured in NM so they pair directly with knots (nautical miles per hour) for time and fuel math.

True Course (TC)

The intended direction of a leg measured against true north, read straight off the sectional chart with a plotter, and it is the starting input from which every heading on the nav log is derived.

Winds Aloft

The forecast wind direction (in degrees true) and speed at your cruise altitude, taken from the winds and temperatures aloft forecast, and because wind pushes the airplane sideways and speeds it up or slows it down, it drives the wind correction angle and ground speed.

True Airspeed (TAS)

Your actual speed through the air after correcting indicated airspeed for altitude and temperature, and combined with the winds aloft it determines your ground speed and the heading needed to hold course.

Magnetic Variation (VAR)

The local angular difference between true north and magnetic north (shown on charts as isogonic lines, east or west), applied to true heading because your compass points to magnetic north, not true north.

Compass Deviation (DEV)

The small error caused by the airplane's own metal and electrical systems pulling on the compass, listed on the compass correction card, and it is the final adjustment applied to get the heading you actually fly on the wet compass.

Wind Correction Angle (WCA)

The number of degrees you turn into the wind so the airplane tracks the desired course instead of drifting downwind, computed by the nav log from the winds aloft and your true airspeed and added to or subtracted from true course.

True Heading (TH)

The direction the airplane's nose must point relative to true north to stay on course, found by applying the wind correction angle to the true course, and it is the first computed heading in the chain toward what you actually fly.

Magnetic Heading (MH)

True heading corrected for magnetic variation, giving the direction relative to magnetic north that matches your heading indicator and most published headings.

Compass Heading (CH)

Magnetic heading corrected for compass deviation, and this is the final number you actually fly and steer by on the magnetic compass.

Ground Speed (GS)

Your true speed over the ground in knots after the wind is accounted for (a headwind lowers it, a tailwind raises it), and it is the value that turns leg distance into time en route and fuel burned.

Estimated Time En Route (ETE)

The predicted time to fly a leg (or the whole route), computed from leg distance divided by ground speed, and it feeds both your arrival estimate and your fuel planning.

Estimated Time of Arrival (ETA)

The clock time you expect to reach a checkpoint or destination, found by adding each leg's ETE to your takeoff or checkpoint time, and comparing actual arrival to ETA is how you catch wind or planning errors in flight.

Leg Fuel and Fuel Remaining

Leg fuel is the amount burned on a segment (leg ETE times your fuel burn rate in gallons per hour) and fuel remaining is what is left in the tanks after it, and tracking both leg by leg confirms you will land with your required VFR reserves (30 minutes day, 45 minutes night at normal cruise) plus a safety margin.

Dead Reckoning (DR)

Navigating by calculation, using known heading, airspeed, wind, and time to predict where you will be and when, and the nav log's headings, ground speeds, and ETAs are all products of dead reckoning.

Pilotage

Navigating by visually identifying landmarks and comparing them to the chart, used to verify each checkpoint and confirm the dead reckoning plan is actually working.