Dead reckoning

One of the tasks on the private pilot checkride is labeled “pilotage and dead reckoning.” Both methods of navigation require good visual conditions in order to work. Pilotage is defined in the FAA’s Pilot’s Handbook of Aeronautical Knowledge as navigation by reference to landmarks or checkpoints (except over water) that often is used in conjunction with dead (from ded, meaning deduced) reckoning. So what’s dead reckoning? In the navigation chapter you’ll find that dead reckoning is navigation solely by means of computations based on time, airspeed, distance, and direction. The key word is computations. It’s one of the things you learn in ground school.

Dead reckoning is a navigation technique that calculates an aircraft's current position based on its previous known position, heading, speed, and time. It's essentially a method of estimating where you are by accounting for the distance traveled in a specific direction.

How it works

1. Start with a known position: This could be a starting point, a checkpoint, or a previous fix.

2. Calculate the distance traveled: This is done by multiplying the groundspeed (speed over the ground) by the time elapsed.

3. Account for wind: Wind can affect the aircraft's groundspeed and heading, so it needs to be factored into the calculation.

4. Determine the new position: By combining the distance traveled with the initial position and accounting for wind, you can estimate the aircraft's current position.

When is it used?

As a backup: Dead reckoning can be used as a backup navigation method if primary navigation systems (like GPS or radio aids) fail.

In areas with limited visibility: When landmarks are obscured (e.g., in clouds, over water), dead reckoning can still provide a way to navigate.

For basic navigation: It's a valuable tool for basic cross-country flights and for learning the fundamentals of navigation.

Limitations

Accuracy decreases over time: Errors in speed or heading estimations can accumulate over time, leading to inaccuracies.

External factors: Wind, currents, and changes in terrain can affect the accuracy of dead reckoning calculations.

Need for corrections: It's important to periodically verify dead reckoning calculations with external references (like landmarks, radio aids, or GPS) to minimize errors.