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KIAS --> MPH Conversion

Pro Member Chief Captain
Jonathan (99jolegg) Chief Captain

Hi,

Does anyone know of a simple way to convert Knots Indicated Air Speed to Miles Per Hour?

Thanks 😉

16 Responses

Pro Member First Officer
Canyon (NoWorries) First Officer

1 knot = 1.15 mph

Pro Member Trainee
ger_01 Trainee

i have a site where u can type in the numbers..
http://www.digitaldutch.com/unitconverter/
make sure u select 'speed' on the left side.. the select knots as the input and miles as the output.

1 knot = 1.150779 miles/hour

Pro Member Chief Captain
Jonathan (99jolegg) Chief Captain

Ok thanks guys 🍻

Guest

99jolegg wrote:

Hi,

Does anyone know of a simple way to convert Knots Indicated Air Speed to Miles Per Hour?

Thanks 😉

Surely if it is an 'indicated' airspeed then there is no formula for it? It all depends on what height you are and wind speed blah de blah.

330KIAS at 15000ft is not the same as 330KIAS at 35000ft.......well, it would normally show as 290KIAS in the 737 I fly.

Hopefully if I am wrong someone will point me in the right direction.

Don Wood Guest

The last guest posting is correct. Indicated airspeed compared to miles per hour is akin to comparing apples to camels.

The calculatiion that does make sense is to compare groundspeed in knots to miles per hour.

Indicated airspeed is not only effected by altitude but by relative wind. If you have an indicated airspeed at any given altitude of 150 knots, your groundspeed can vary significantly depending on whether you have a head wind or tail wind and the velocity of that wind.

I was flying a Piper Cub once through the Dagget area in California. I had an indicated airspeed of 65 mph (no knot indicators on a Cub) but I was actually moving backwards over the ground due to a vicious headwind coming through Banning Pass.

Pro Member Chief Captain
Manuel Agustin Clausse (Agus0404) Chief Captain

I was always wondering what do you have to do when a person is flying backwards because of high head winds...
If you turn the airplane, the wind can make you spin around. So what do you have to do? Can you descend and slowly turn the airplane?

Don Wood Guest

Agus040: I'm not sure what you mean "the wind can make you spin around". The effect on the air foil (the wing) is not impacted by the planes movement or lack of movement over the ground. You can turn as easily in a strong wind as in no wind, although there may be more turbulance. What is effected is the airplanes track over the ground.

In the described conditions, when you turn from a head wind condition to a tail wind condition, the relative airspeed remains the same-whatever your combination of power, altitude, and attitude produces as indicated airspeed. As you begin your turn, your groundspeed increases proportionally to the completeness of the turn. Once you have a pure tailwind, your groundspeed will be the sum of your actual airspeed (indicated airspeed corrected for atmospheric conditions and instrument error) and the velocity of the tailwind.

The one condition where the wind can effect the ability of the airplane to maintain lift is wind shear. In this case, you go suddenly from a headwind to a tail wind while the aircraft remains on the same course. That is no big thing if it occurs at sufficent altitude to correct for it. It has been a major cause of accidents when it occurs close to the ground during approach and the pilot is late recognizing it or the aircraft has insufficient power to quickly overcome the loss of lift.

Pro Member Chief Captain
Manuel Agustin Clausse (Agus0404) Chief Captain

Thank you for that, Don Wood!

In this phrase: "the wind can make you spin around" I meant that the wind can make the airplane to turn over itself. What happens if a person is flying against the wind and then the person turns right the airplane with a 30° of bank angle? Can the wind make the airplane to turn over itselft because the left wing is higher than the right wing?

crosscheck9 Guest

Agus0404 - I'm not too sure of myself, so you may want some confirmation, but I don't think that can happen. First, because of the weight of the aircraft, and second, because of the wind direction in relation to the Airplane's direction. If you had a very strong crosswind, well maybe. You might want someone to check and see if I'm right.

Pro Member Chief Captain
Manuel Agustin Clausse (Agus0404) Chief Captain

You are probably right, crosscheck.

I was just wondering anyway... I'll learn that later when I start my pilot carrer.

Don Wood Guest

A too-strong cross wind on landing can definately cause an aircraft to upset. However, assuming wind conditions that any sane pilot would fly in, a turn at altitude is not a dangerous manuever. These were not the conditions posed by the original question. That question was about the propensity of an aircraft to "spin around" when it turned away from a strong wind while in cruise. My responses were also not meant to apply to cyclonic winds such as tornados, hurricanes, etc or to thunderstorms. It would be insane to try and fly in those conditions unless you are especially trained and your aircraft is specially equipped for such storm penetrations.

spuddi Guest

in theory, although I never dare try it, in a glider you can perform a "no turn" circuit. if the wind is strong enough you can take off into wind and then your ground speed is actually a minus figure so that in effect you are flying backwards then you can nose down and land again on the same runway.

Pro Member Trainee
jaapverduijn Trainee

Some guys are mixing some things up here somehow (grin)! OF COURSE you can convert KIAS to "miles per hour". The K stands for "knot", which is one nautical mile per hour, which can easily be converted to one "land mile" per hour". Height, windspeed, or whatever outside influences are irrelevant here. Simply convert from nautical miles to "land" miles (1 nautical mile = 1.150779 "land" mile), so an indicated airspeed of 100 knots is the same as an indicated airspeed of roughy 115 m.p.h.

Be well!

Jaap Verduijn.

Pro Member Trainee
jaapverduijn Trainee

Greetings Agus!

"(...) What happens if a person is flying against the wind and then the person turns right the airplane with a 30° of bank angle? Can the wind make the airplane to turn over itselft because the left wing is higher than the right wing? (...)"

No, of course not. Why would it? Or rather: why could it? As far as your aircraft is concerned, you're flying in totally still air regardless of whatever (constant) windspeed you might be in. It's only in regard to the EARTH that windspeed plays a role, but you can always think of your aircraft flying in totally still air, where only its AIRspeed is relevant to its behavior, not its GROUNDspeed.

WindsSHEAR, as a poster rightly remarked, is a different thing altogether. But that's not what this present issue is about.

Be well!

Jaap Verduijn.

Pro Member Chief Captain
Manuel Agustin Clausse (Agus0404) Chief Captain

Thank you Jaap! That was an interesting post 😉

Pro Member Trainee
jaapverduijn Trainee

You're welcome!

Jaap Verduijn.

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