A knot is a unit of speed that equals one nautical mile per hour. This is the most common unit of measure for the airspeed of an aircraft, and it is equal to 6,080 feet, or about 1.15 miles. The unit is abbreviated kn, kt, or kts, but they all mean the same thing. Here is a simple calculation to roughly estimate miles per hour compared to knots:
1 international knot is equal to:
- 1 Nautical Mile per hour,
- 1.852 Kilometers per hour,
- 0.514 Meters per second,
- 1.1507 Miles per hour (roughly).
The origin of the word "knot" comes from ocean vessels. Until the 19th century, a ship used a "chip log" to measure their speed and distance traveled. This was done by throwing a weighted wooden panel off of the stern of the ship. The wooden panel was tied to a rope with evenly spaced knots tied to it. As the line was run out by the movement of the ship, a sailor counted the number of knots that passed by him and timed how long it took for the line to fully cast all the way out. The sailor could then calculate the speed of the ship and add the distance to the total that the ship had traveled on their current journey. He then pulled the weight back in and threw it off the back of the ship to start counting again.
While the term "knot" was originally devised for maritime vessels, it has now come to describe the speed of a craft in a fluid. Because air acts as a fluid while an aircraft moves through it, the terminology was also adopted by aviators. To make sure that there is no confusion while in the aircraft, wind speed, airspeed, and ground speed are all given in knots, while distance is given in nautical miles. This makes estimated arrival times and map reading much easier to calculate for a pilot.
Knots are a measure of speed that is accepted worldwide, as much of the terminology in the aviation industry is. This is mostly to avoid confusion or possible accidents for pilots that are flying internationally. Instead of 120 sets of rules or speeds to follow, all they have to do is go by one international code.