# knots and kias

Taylor First Officer

Hello, everyone. I was just wondering if there is a difference between KIAS and Knots. I see normal planes fly at, let's just say, 450 knots but in FSX I can only go to around 340 KIAS. And, where are the knots displayed in the 737? thanks and any help is appreciated.

CRJCapt Chief Captain

Taylor wrote:

hello everyone. i was just wondering if there is a difference in kias and knots. i see normal planes fly at, lets just say, 450 knots but in fsx i can only go to around 340 kias. and where is the knots display in the 737? thanks and any help appreciated. 😀 😀

A Knot equals 1 nautical mile per hour. A nautical mile is 6076 ft. A statute mile (normal mile as in your car) is 5280 ft.

KIAS is knots indicated airspeed. It's the speed in knots that the aircrafts airspeed indicator shows and lessens as an aircraft climbs due to less dense air at higher altitudes. This value is shown on the left side of the Primary Flight Display(PFD).

KTAS(Knots true airspeed) is the true speed of the aircraft thru the air. As an aircraft climbs, the air becomes less dense and KIAS decreases. An aircraft that is traveling at 450 KTAS would only show about 290 KIAS at 30,000 ft.

Taylor First Officer

o ok thanks

Ian Stephens (ianstephens) Captain
Ian Stephens is an expert on this topic. Read his bio here.

Great question! To answer your query, let's dig a bit deeper into what these terms represent and their use in flight simulation.

Knots is a unit of speed used in aviation, equal to one nautical mile per hour. The term KIAS, on the other hand, stands for Knots Indicated AirSpeed. This refers to the speed of an aircraft as read directly from its airspeed indicator. This measurement is calibrated to reflect the speed at sea level under International Standard Atmosphere (ISA) conditions (i.e., at a temperature of 15 degrees Celsius and pressure of 1013.25 millibars).

1. In general, the KIAS is affected by air density. As you ascend, the air gets thinner (lower density) and the KIAS starts to decrease even if your actual speed (True AirSpeed or TAS) remains the same. This is why you may notice a lower KIAS at high altitudes compared to sea level.
2. The discrepancy you mentioned between normal planes flying at around 450 knots and the FSX's limit of 340 KIAS is due to this difference in air density at varying altitudes. It is not uncommon to see commercial jets like the Boeing 737 cruising at high speeds around 450 knots (TAS) at high altitudes, while their indicated airspeed (KIAS) would be significantly lower.

As for the display of knots in the 737, in both FSX and its successors Microsoft Flight Simulator 2020 and X-Plane 12, you can find this information on the Primary Flight Display (PFD), specifically on the airspeed indicator located on the left side. It displays the current speed of the aircraft in knots (KIAS).

To clarify further:

1. In the center of this gauge, you'll find a digital readout of your current KIAS.
2. The rolling scale to the left of this readout represents speed increments, with major tick marks typically indicating intervals of 10 or 20 knots.

I hope this clears up your question. Feel free to follow up if you have any other inquiries. Safe flying!