The Navigation Log, the Five-Step Chain from True Course to Compass Heading, and the Pre-Cross-Country Planning Foundation GPS Made Students Think They Could Skip

The navigation log converts a line drawn on a sectional chart into a heading you can actually fly, a groundspeed you can use, and a fuel plan you can trust. There are five distinct corrections between your chart measurement and the number you dial into your heading indicator. Most student pilots approaching their first solo cross-country can explain two or three of them. This article covers all five - and why each one exists.

What Is a Navigation Log and What Do All Those Columns Mean?

The nav log form looks like alphabet soup the first time you see it: TC, Var, MC, Dev, CC, TAS, WCA, GS, Dist, Time, Fuel. Each column represents a translation - a conversion from one frame of reference to another. The chain only works if you understand what each conversion is actually doing.

Working through a nav log from scratch isn’t just a training exercise. It’s the process that forces you to make real decisions before you ever start the engine.

How Do You Measure True Course From a Sectional Chart?

Pull out your sectional and a plotter. Draw your route, then measure each leg against the lines of longitude printed on the chart. Longitude lines run exactly north to south relative to true north - the geographic north pole, the top of Earth’s rotational axis - so measuring against them gives you a true direction.

A leg that measures out to 120 degrees is 120 degrees true. That’s your starting point for every downstream calculation.

What Is Magnetic Variation and How Do You Apply It?

True north and magnetic north are not in the same place. Magnetic north is where the planet’s magnetic field converges - currently somewhere in northern Canada - and the angular difference between true north and magnetic north, measured from your location, is called magnetic variation. It changes depending on where you are.

On the sectional, look for faint lines running roughly north to south with degree values printed on them. Those are isogonic lines - they connect points of equal magnetic variation. Flying in the eastern United States, you might cross lines labeled 7 or 8 degrees west. In western Montana, you might see 15 or 16 degrees east.

The memory aid: east is least, west is best. East variation, subtract it. West variation, add it. In a 10 degrees west area: 120° true + 10° west variation = 130° magnetic. That’s step one - you’ve accounted for the difference between the geographic axis and the magnetic field.

What Is Compass Deviation and Where Do You Find It?

Your magnetic compass doesn’t read the magnetic field perfectly either. The airplane generates its own local magnetic interference - the engine block, the alternator, the avionics, the wiring. All of it nudges the needle by a small amount that’s unique to your specific aircraft and can vary depending on which direction you’re headed.

Look for the compass correction card mounted near the compass in the cockpit. It’s a small printed table listing something like: steer 360 to indicate north, steer 092 to indicate east. Interpolate between those values for headings in between. If the card shows +2 degrees for your heading, add two. Minus one, subtract one.

On a magnetic course of 130 degrees with a deviation of +2, compass course becomes 132 degrees. Running tally: true course 120 → variation +10 → magnetic course 130 → deviation +2 → compass course 132.

How Do You Use the E6B to Calculate Wind Correction Angle and Groundspeed?

Your airplane moves through the air at its true airspeed (TAS). But the air is itself moving over the ground. If a crosswind pushes from the left while you’re pointing toward your destination, your actual track over the ground curves right of your intended course. The angular offset you angle into the wind to compensate is the wind correction angle (WCA).

The E6B’s wind side - the circular slide rule also called the Dalton computer - calculates this with a rotating disc, a transparent slide card with a grid, and a center grommet. Set the wind direction on the outer ring, mark a dot for wind velocity, rotate the disc to align your true course with the index, then slide the card until the dot aligns with the arc matching your TAS. The dot’s left-right offset gives you the WCA. The arc value where the dot sits is your groundspeed.

With winds from 200° at 22 knots, a TAS of 110 knots, and a true course of 120°, the wind triangle produces a correction angle of about 7 degrees left and a groundspeed of roughly 126 knots - that wind has a tailwind component. Those numbers change everything downstream.

How Do Time and Fuel Flow From Groundspeed?

Groundspeed is the number your entire time and fuel calculation depends on. At 126 knots over the ground on a 90 nautical mile leg, you cover that distance in about 43 minutes. At a fuel burn of 8 gallons per hour, that leg costs roughly 5.7 gallons.

Change the winds, change the groundspeed, change the time and fuel. Do this calculation for every leg, add it up with your reserves, and you have a complete nav log.

How Do You Choose Checkpoints for a Cross-Country Flight?

The nav log isn’t just a planning document - it’s your in-flight position-keeping system. Space checkpoints roughly every 10 to 15 minutes of flight time. A good checkpoint is unambiguous: you can’t mistake it for something similar along the same route, it’s visible from cruise altitude, and you can find it on the sectional before you leave the ground.

Highways work if they have a distinctive interchange. Airports are excellent because you can verify them by identifier. Railroads, reservoirs with distinctive shapes, rivers with unusual bends, ridgelines with specific contours - all are valid if they meet the unambiguous test.

Before your first solo cross-country, pull up a satellite overlay in your planning tool and spend 15 minutes looking at each checkpoint from above. The sectional is an abstraction. The more exposure you have to what a landmark actually looks like from altitude, the faster you’ll spot it from the cockpit.

How Do You Use Checkpoints to Catch Wind Forecast Errors in Flight?

Mark your estimated time over each checkpoint in the nav log. When you cross it in flight, write down the actual time. Arriving early means better groundspeed than planned. Arriving late means you’re slower. Use the first leg as a calibration gate, not just a waypoint - update your fuel estimate before the second leg.

If the winds are significantly different from the forecast, you want to know that within the first 20 minutes of flight - not over the mountains two hours in.

What Does the Checkride Evaluator Look for in Your Navigation Planning?

The Airman Certification Standards (ACS) for the private pilot certificate require you to demonstrate navigation by pilotage and dead reckoning without relying on the moving map as a primary reference. The evaluator may ask you to set aside the GPS and locate your position using the chart, elapsed time, and visual landmarks. Your navigation log is what makes that possible.

The evaluator is also reviewing your complete planning package: weather briefing documentation, weight and balance, performance calculations for departure and destination, and the nav log itself. Bring everything and show your work on every calculation. The evaluation checks whether you planned this flight before you got in the airplane.

How Much Fuel Reserve Should You Actually Plan?

The FAA requires 30 minutes of fuel reserve at cruise power for daytime VFR operations and 45 minutes for night. Those numbers assume everything went according to plan - winds matched the forecast, no weather reroutes, no holds for traffic. They are a legal floor, not a planning target.

A more conservative practice: plan to land with at least one hour of fuel remaining. If a fuel stop adds 30 minutes to your trip but eliminates a potential fuel emergency over unfamiliar terrain, that’s 30 minutes well spent. The nav log is where you make that decision at the kitchen table, before it becomes a cockpit judgment call.

Key Takeaways

• The five-step chain - true course → apply variation → magnetic course → apply deviation → compass course → apply wind correction → compass heading - must be completed in order; each step corrects for a different source of error.
• East is least, west is best: subtract east variation, add west variation to convert true course to magnetic course.
• Compass deviation is aircraft-specific and heading-dependent; always check the correction card in that airplane.
• Groundspeed, not airspeed, drives all time and fuel calculations - work the wind triangle on the E6B before you commit to any fuel plan.
• The first checkpoint after departure is a calibration gate: compare actual time to estimated time and update your fuel math before the next leg.