Time and Distance Calculations

The Speed, Distance, Time Formula

The core formula for time and distance calculations in aviation is:

• Time = Distance ÷ Speed
• Distance = Speed × Time
• Speed = Distance ÷ Time

This relationship is used throughout flight planning and navigation, whether calculating leg times, estimating arrival, or verifying fuel requirements. For example, if you know your groundspeed and the distance between two waypoints, you can quickly find the time it will take to fly that segment.

Units and Conversions

Aviation distances are usually measured in nautical miles (NM), but you may encounter kilometres (km), statute miles (SM), or feet (ft). Remember:

• 1 NM = 1.852 km = 1.1508 SM = 6,076 ft Always use consistent units in your calculations to avoid errors.

Air Distance vs. Ground Distance

• Air Distance (NAM): The distance flown through the air, affected by true airspeed (TAS).
• Ground Distance (NM): The actual distance covered over the ground, affected by groundspeed (GS).

The conversion formula is:
NAM = NM × TAS / GS This accounts for wind and altitude effects, ensuring accurate fuel and time planning.

Calculating New Positions

When given a starting latitude/longitude and a distance flown north-south or east-west, you can determine your new position. For same meridian (longitude), only latitude changes; for same parallel (latitude), only longitude changes. Calculations must consider the convergence of meridians as you move away from the equator.

Time Zones and LMT/UTC

Pilots must convert between Local Mean Time (LMT) and Coordinated Universal Time (UTC) for accurate flight logs and ATC communication. Crossing the International Date Line requires adjusting the date forward or backward by one day, depending on direction.

Practical Use: Navigation Computers

Flight computers (like the CRP-5) streamline these calculations. By aligning scales for speed and time, you can quickly solve for any unknown variable, which is a common exam and operational task.