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What is ground speed versus air speed and why is the difference important? Howdo you compute one if you have the other?

Stratmando

If you are moving by Air or by Water, Currents and winds will affect your "Speed over ground", It is what a GPS will tell you,
If you are going 60 Miles per hour in a 30 mile an hour head wind, a GPS will tell you you are moving 30 MPH of Speed made Good, or Speed over ground(Civilian) This may mean you need twice as much fuel, kind of Important.
With No Islands in sight, it can SXXK
It will help in determining your arrival. VERY important.

FlyYakker

Stratmando is correct. Air speed is measured relative the the air the plane is moving in; ground speed merely measures the resulting actual velocity over the ground. Also consider that if you try to take off with a 30 MPH tail wind and your plane requires a 60 MPH air speed to gain enough lift to fly, you will have a 90 MPH ground speed before you have the lift needed to fly. It's tough on landing gear and, on a short runway, you may run out of runway before lifting off. That is why airplanes always stake off facing the wind, or as nearly so as possible depending on available runway alignment. A similar issue is present on landing, so airplanes always land heading into the wind, or a close as possible.

tanny242

i dont know what is the difference between air speed and ground speed!!like in kn or something

Stratmando

Hopefully the 2 above post will explain.
You compare both at Miles Per Hour OR
Kph.

Flying Blue Eagle

TANNY242 - THE two of them explained it very well; I will try:: IF you weere in a air plane and you had a air speed indicated on the air speed insturment as being indicated 200 mph, ok now say you have a head wind (WIND BLOWING AGAINST THE FRONT AF YOUR PLANE) AT SAY 30 MPH, YOUR GROUND SPEED OVER THE GROUND <WOULD BE (200MPH MINUS 30 MPH =170 MPH OVER$ THE GROUND:: NOW IF IT was turned around and it was atail wind you would add the 30mph to the 200mph, now that would make your travel over the gropund 230 mph:: NOW IF YOU WANT TO CHANGE MPH TO KNOTS ( MULTIPLY THE MPH x!.8 to = knotsIF YOU HAVE ANY MORE TROUBLE ON THIS QUESTION JUST COME BACK TO THIS POST<
AND HOLLER AND ONE OF US PILOTS WILL TRY TO HELP YOU OUT: HAVE A GOOD DAY AND GOD BLESS:: F.B.E. (EAGLE 1 out)