15.2 Pilotage and Dead Reckoning
Key Takeaways
- Pilotage is navigation by reference to visible landmarks. Dead reckoning is navigation by time, speed, heading, and distance from the last known position.
- PAR and ACS PA.VI.A expect both methods on the same flight: pick checkpoints you can actually see, compute an ETA to each one, and treat a late or early arrival as drift or groundspeed error — not as a reason to stare at the GPS and stop looking outside.
- A useful checkpoint is unique, charted, and visible from several miles at your altitude: a shoreline bend, a town-plus-rail-plus-highway intersection, a lake with a distinctive shape. “The next cornfield” is not a checkpoint.
- At night, unlighted roads, rivers, and small towns disappear. Plan lighted airports, cities, beacons, and shorelines; carry more time between fixes; and do not invent a checkpoint from a dark hole in the windshield.
- An electronic flight bag (ACS PA.I.D.K1a) is a supplement. You still have to understand the chart, the wind triangle, and the fuel numbers when the battery, the database, or the own-ship symbol fails.
ACS PA.VI.A.K1 is one sentence that fails people who treat “GPS direct” as a method: pilotage and dead reckoning. PA.VI.A.K4 then asks you to select a route, altitudes, and checkpoints. PA.VI.A.K7 asks what you do when the planned numbers and the airplane disagree. This section is the how. The magnetic/E6B arithmetic is 15.3; the fuel-reserve and flight-plan paperwork is 15.4.
Two methods, one cockpit
Pilotage is navigation by matching the world outside to the chart: fly from a recognizable landmark to the next one. You are never more lost than the distance to the last thing you positively identified. Dead reckoning is navigation by computation from a known position: hold a heading, hold a true airspeed, apply the wind you planned, and after a measured time you should be a measured distance along the course. PHAK Chapter 16 is blunt that dead reckoning without a visual check is how a 10-degree heading error becomes a 10-mile miss after 60 miles.
You combine them on every VFR cross-country that PAR cares about. Before takeoff you plot the true course, apply wind to get a heading and a groundspeed, and write an estimated time of arrival at each checkpoint (dead reckoning). In the air you look at the checkpoint when the clock says you should (pilotage). If the town is still two miles left of the nose, you have drift. If the town is on the nose but three minutes late, you have a groundspeed error. You fix the heading or revise the ETA — you do not “average” a 15-degree error and hope the destination airport appears.
| Method | What you use | What fails it |
|---|---|---|
| Pilotage | Unique, charted, visible landmarks | Night, haze, snow, flat terrain, looking at the moving map instead of the window |
| Dead reckoning | Heading, time, TAS/GS, last known fix | Uncorrected compass, wrong wind, no clock, no log |
| Combined (the ACS answer) | Planned heading and ETA, confirmed by the next checkpoint | Either method used alone for the whole trip |
Checkpoints that actually work
PA.VI.A.K4c is selection, not “any town.” A checkpoint should be:
- Unique. One isolated lake with a dam is better than the fifth rectangular field.
- Charted at a scale you can see. A water tower that is on the sectional is useful; a water tower that exists only in the real world is a trap.
- Visible from several miles at your altitude. A 4-lane highway/rail/river junction works at 3,500 MSL. A dirt road does not.
- Spaced so the clock means something. Roughly 10 to 15 nautical miles (about 6–10 minutes at trainer groundspeeds) is the usual training interval. Sixty miles with no intermediate fix is how you discover the error after you are already lost.
First checkpoint after takeoff is often top of climb onto the first course, not the departure end of the runway. Last checkpoint before the destination is something that still works if you have to break off into the pattern or divert — a town or a shoreline before the Class D ring, not the rotating beacon you will only see if you already found the airport.
When the checkpoint is early, late, or off to one side, PA.VI.A.K7 is the skill: planned versus actual. A consistent left miss means a left wind you did not plan or a heading you are not holding. A consistent late arrival means more headwind or less TAS than planned. Change one thing, write the new ETA, and look at the next fix. Do not stack three silent corrections and then wonder why the fuel remaining no longer matches the nav log.
Drift, ETA, and the log
Dead reckoning gives you a true heading and a groundspeed. The heading is what you put on the heading indicator after you set it to the compass in straight, unaccelerated flight. The groundspeed times the remaining distance is the time to the next fix. Add that time to the time you were over the last fix and you have the ETA. If you cross the checkpoint 4 minutes late, the next ETA moves 4 minutes unless you also change groundspeed (a climb, a new wind, a power change). Students who “make up” the four minutes by staring harder at the GPS still have a 4-minute fuel error.
A paper or EFB nav log is how you notice the error. Opening a moving map and watching the airplane icon is not the same as knowing whether you are on the planned line. If the icon dies, the last time/heading/distance you wrote down is your position.
Night — the checkpoint list shrinks
Unlighted terrain goes black. Roads, small rivers, and even medium towns vanish unless they throw light. What still works: lighted airports and their beacons, larger cities, shorelines against a moonlit lake or the ocean, and sometimes a well-lit interstate. What does not work: “the bend in the creek,” a water tower, a small village, a ridgeline. Plan longer legs between lighted fixes, a higher cruise if terrain and 91.159 allow (more glide, more radio line-of-sight, more time to see a beacon), and a personal night minimum tighter than the legal 91.155 night numbers. If your entire route is dark farmland between two 2,000-foot unlighted strips, that is a routing problem, not a “fly the heading harder” problem.
Night also lies. A distant bright town looks closer than it is. Ground lights and stars mix. Fly the heading, fly the time, and do not descend toward a cluster of lights until you have identified the airport — lost procedures in Chapter 16 exist because people chase the wrong glow.
Electronic flight bags are a supplement
ACS PA.I.D.K1a added EFB use as a knowledge element; PA.I.D.R7 added EFB risk. The 2024 ACS note even allows a computer-generated flight plan on the practical test. None of that retires pilotage or dead reckoning.
An EFB is current only if you confirmed the chart cycle, the obstacle database, and the download before engine start. Own-ship position is a GPS estimate, not a checkpoint. A dimmed tablet on a 20 °C night dies about the time you most wanted the next airport diagram. ForeFlight or any other brand does not know your personal fuel-flow conservatism, does not file or activate a VFR flight plan unless you tell it to, and will happily draw a magenta line through a hot restricted area if you never looked.
Use the EFB to build the log, brief the SUA and TFRs, and cross-check the next checkpoint. Then look outside and fly the heading. If you cannot explain the true course, the wind correction, and the 91.151 fuel number without the glass, you do not yet understand the trip — and that is what PAR and the DPE are testing.
PAR scenario: you planned 12 minutes to a T-shaped lake at 5,500 MSL. At 12 minutes the lake is a mile right of the nose. That is drift, not a broken clock. Note the time you actually arrived, turn a few degrees right to recapture the line, and write a new ETA for the next town. Do not twist 20 degrees and then chase the magenta line on the tablet. The lake was the truth; the tablet is the suggestion.
A private pilot is navigating VFR by holding a computed heading and using a clock and planned groundspeed from the last identified town. Which method is that, and what must be added to satisfy ACS PA.VI.A?
Why does a night VFR cross-country need a different checkpoint plan than the same route by day?
ACS PA.I.D.K1a addresses use of an electronic flight bag. What is the knowledge-test-level role of an EFB on a VFR cross-country?