Navigating The Skies A Comprehensive Guide to Calculating 68 Knots

How to calculate 68 knots


Navigating the vast expanses of the sky is an intricate art that demands precision and a keen understanding of various aviation concepts. One such critical skill is calculating airspeed, often measured in knots. In this article, we will delve into the world of aviation and explore how to calculate a specific airspeed, 68 knots, while offering valuable insights into its significance and practical applications.

Understanding Knots

Before we dive into the specifics of calculating 68 knots, it’s essential to understand what a knot is. A knot, in aviation terms, is a unit of speed equivalent to one nautical mile per hour. A nautical mile is slightly longer than a regular mile (1.15078 statute miles), making knots a more suitable measurement for aviation due to its consistency across the globe.

Why 68 Knots?

Airspeed is a fundamental parameter in aviation, and pilots frequently use various speeds for different phases of flight. So, why is 68 knots significant? One of the primary uses of this speed is in the context of general aviation, where it often represents the approach speed for smaller aircraft during landing. Calculating 68 knots is crucial for ensuring a safe and controlled landing.

The Formula for Calculating True Airspeed (TAS)

To calculate 68 knots, we first need to understand the concept of True Airspeed (TAS). TAS is the actual speed of an aircraft relative to the air mass in which it is flying. It takes into account factors such as altitude, temperature, and pressure. The formula to calculate TAS is as follows:

\[TAS = IAS \times \sqrt{\frac{\rho}{\rho_{0}}}\]


TAS = True Airspeed

IAS = Indicated Airspeed (the speed shown on the aircraft’s airspeed indicator)

ρ = Air density at the current altitude and temperature

ρ0 = Standard air density at sea level (approximately 1.225 kg/m³)

Now, let’s break down the steps to calculate 68 knots

Determine the Indicated Airspeed (IAS)

The first step in calculating 68 knots is to determine the Indicated Airspeed (IAS) your aircraft is currently flying at. This is the speed displayed on your airspeed indicator in the cockpit.

Find the Air Density (ρ)

Air density varies with altitude and temperature. To calculate TAS accurately, you’ll need to obtain the air density at your current altitude and temperature. This information is typically available from onboard instruments or weather reports.

Calculate Standard Air Density (ρ0)

Standard air density (ρ0) is the air density at sea level and is approximately 1.225 kg/m³. This value remains constant for most calculations.

Apply the Formula

Now, plug the values from Steps 2 and 3 into the TAS formula

\[TAS = IAS \times \sqrt{\frac{\rho}{\rho_{0}}}\]

For our target of 68 knots, plug in the value of 68 knots for IAS. Keep in mind that you’ll need to convert knots into meters per second to match the units of airspeed (m/s) with the units of air density (kg/m³) used in the formula. The conversion factor is 1 knot ≈ 0.514444 m/s.

Example Calculation

Let’s say your IAS is 68 knots, and the air density at your current altitude and temperature corresponds to 1.05 kg/m³. Applying the formula:

\[TAS = 68 \times 0.514444 \times \sqrt{\frac{1.05}{1.225}}\]

Solving this equation will give you the True Airspeed (TAS) in knots.

Frequently Asked Questions

How do you calculate knots?

One knot equals one nautical mile per hour, or roughly 1.15 statute mph. The term knot dates from the 17th century, when sailors measured the speed of their ship using a device called a “common log.”

What does 15 knots mean?

One Knot = One nautical mile per hour. Light Winds – Wind speeds of 1 – 14 knots (1-16 mph or 1-26 km/h) Moderate Winds – Wind speeds of 15 – 19 knots (17-22 mph or 28-35 km/h) Strong Winds – Wind speeds of 20 – 33 knots (24-37 mph or 39-54 km/h) Gale – Wind speeds of 34 – 47 knots (39-54 mph or 63-87 km/h)


Navigating the skies is an art that requires a deep understanding of various aviation concepts, including airspeed calculations. Calculating 68 knots, specifically in the context of approach and landing, is crucial for ensuring a safe and controlled descent for smaller aircraft. By mastering the formula for True Airspeed (TAS) and following the steps outlined in this article, pilots can confidently calculate and maintain this essential speed, contributing to safer and more precise flights in the world of aviation.

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