Pilotage & dead-reckoning techniques

Pilotage is flying by what you can see. Dead reckoning is flying by what you calculated. Real cross-country navigation runs both at once — the chart confirms the math, and the math predicts the chart.

Pilotage: flying by what you can see

Pilotage is navigation by reference to visible landmarks. You draw a course line on the sectional, choose checkpoints along it, and confirm your position as each one slides past the window.

The whole technique rests on good checkpoints:

• Unique and unambiguous — a town where a highway and a railroad cross a river, a distinctively shaped lake, an isolated peak. One lake among ten parallel lakes tells you nothing.
• Spaced about 5–10 NM apart — close enough to catch drift early, far enough that you're not heads-down the whole leg.

Reading the chart itself — terrain, symbols, choosing the checkpoints — is its own skill, covered in K3.

Dead reckoning: the heading-and-time computation

Dead reckoning computes your position from a known starting point using heading, true airspeed, wind, and time. It's the math that predicts where pilotage should confirm you are. Three inputs feed the computation:

• True airspeed (TAS) — indicated airspeed corrected for altitude and temperature (density altitude). TAS runs roughly 2% higher per 1,000 ft, so the higher and warmer you fly, the faster you're actually moving through the air than the airspeed indicator shows.
• Wind — forecast winds aloft give the direction and speed pushing you off your air-mass course.
• Wind correction angle (WCA) — the angle you crab into the wind to hold your desired ground track.

A quick feel for WCA: on a course of 090° at 110 kt TAS with the wind from 360° at 20 kt, that 20-knot wind is a left crosswind, so you crab a few degrees left — roughly a 10° correction — and fly a true heading near 080° to track 090°. The E6B gives the exact angle; the habit is knowing that a 20-knot crosswind on a 110-knot airplane is about ten degrees, so a computed answer of 30° tells you something's wrong.

The conversion chain — TC → TH → MH → CH:

1. True Course (TC) — measured off the sectional against true north.
2. + Wind Correction Angle → True Heading (TH) — the crab angle that holds your track in the wind.
3. ± Variation → Magnetic Heading (MH) — the offset between true and magnetic north; "East is least, West is best."
4. ± Deviation → Compass Heading (CH) — the airplane's own magnetic error, read off the compass correction card.

An E6B or an app runs the wind triangle for you. The point of knowing the chain is so a bad input — wrong wind, wrong variation — doesn't slip through unnoticed.

Groundspeed, ETE, and revising in flight

The plan gives an estimated groundspeed; the flight gives the real one. Time a leg between two checkpoints and the rest falls out — GS = distance ÷ time.

Worked example: two checkpoints 18 NM apart, planned at 10 minutes (≈108 kt). You actually cross the second at 11.5 minutes, so GS = 18 ÷ (11.5 ÷ 60) ≈ 94 kt — slower than planned. Every downstream ETE was built on 108 knots; redo them on 94 or you'll arrive late and short on the fuel estimate.

The navigation log is where this lives — a row per leg with course, heading, distance, planned vs. actual time, and fuel. In flight you fill the "actual" column, and the gap between planned and actual is your early warning. One catch: your planned groundspeed assumes a planned power setting — fly a different RPM and the GS, and every ETE built on it, is wrong. §91.103 requires you to know fuel requirements and alternatives before you launch; the in-flight GS check is how you confirm the plan still holds.

Why you run both with a GPS aboard

A GPS hands you position for free. Pilotage and dead reckoning are the backup already running when the magenta line quits — so treat the GPS as a third opinion, not the only one. The habit of cross-checking it (and the collision risk of not looking outside) is the subject of R1.