Turning radius

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▪︎This content is Not an official document and does not represent the views of Airbus or any other aviation authority.

▪︎The information provided may be incorrect or misinterpreted and should not be relied upon for decision-making. 

▪︎Always refer to official documents and consult with a qualified aviation professional before making any decisions based on the information provided in this blog post.

▪︎The information provided in this blog post is based on personal study and review.

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The turning radius is the distance the aircraft needs to turn. For example, if there’s a CB (cumulonimbus cloud) ahead and we want to deviate, but act too late, we could end up flying into it. To avoid this, we need to know how far the aircraft will travel while turning.

 

For instance, if the aircraft is flying at a certain speed, say 400 knots, and we use a 15-degree bank angle at cruising altitude, the turning radius will be 8.7 nautical miles, as we calculated. This means we need to start turning at least 10 nautical miles before the obstacle, because the aircraft will follow a circular path with a radius of 8.7 nautical miles.

 

Calculation Formula

 

To calculate the aircraft’s turning radius based on speed, the following formula is used in aviation:

R = \frac{V^2}{g \times \tan(\theta)}

Where:

•  R  is the turning radius (in meters or feet),
•  V  is the true airspeed (in m/s or ft/s),
•  g  is the acceleration due to gravity (approximately  9.81 \, m/s^2  or  32.2 \, ft/s^2 ),
•  \theta  is the bank angle of the aircraft during the turn.

This formula helps you understand how the aircraft’s speed and bank angle affect the turning radius. As airspeed increases, the turning radius increases for the same bank angle. To reduce the radius, increasing the bank angle helps, but there are limits for safety and comfort.

 

 

Turning Radius Table

 

Here’s a table of turning radius with a 15-degree bank angle at different ground speeds:

| **Ground Speed (knots)** | **Turning Radius (nautical miles)** |
|--------------------------|-------------------------------------|
| 300 kt                   | 4.9 nm                             |
| 400 kt                   | 8.7 nm                             |
| 500 kt                   | 13.6 nm                            |
| 600 kt                   | 19.5 nm                            |

 

 

When we’re on approach, the aircraft will be in its landing configuration. At this stage, the speed will typically vary between 140 knots and 200 knots. It’s important to calculate the turning radius for these speeds to know when to begin turning, whether it’s from downwind to base, base to final, or during a circling or visual approach.

 

Using the table, we can predict the turning point for these ground speeds. For example, with flaps set to configuration 2, the speed is usually between 140 and 160 knots. If the turning radius at 140 to 160 knots is about 1.2nm to 1.5 nautical miles, we know that the turn should start at least 1.2 or 1.5 nautical miles before reaching the point where the turn needs to be completed.

 

Here’s a table of turning radius with a **25-degree** bank angle at different ground speeds:

| **Ground Speed (knots)** | **Turning Radius (nautical miles)** |
|--------------------------|-------------------------------------|
| 140 kt                   | 1.2 nm                             |
| 150 kt                   | 1.4 nm                             |
| 160 kt                   | 1.5 nm                             |
| 170 kt                   | 1.7 nm                             |
| 180 kt                   | 1.9 nm                             |
| 190 kt                   | 2.1 nm                             |
| 200 kt                   | 2.3 nm                             |