Ask Experts Questions for FREE Help !
    educ8tor1's Avatar
    educ8tor1 Posts: 1, Reputation: 1
    New Member

    Dec 31, 2008, 05:29 PM
    air speed versus ground speed
    What is ground speed versus air speed and why is the difference important? Howdo you compute one if you have the other?
    Stratmando's Avatar
    Stratmando Posts: 11,188, Reputation: 508
    Uber Member

    Dec 31, 2008, 06:14 PM

    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's Avatar
    FlyYakker Posts: 378, Reputation: 41
    Full Member

    Jan 1, 2009, 06:38 PM

    Stratmando is correct. Air speed is measured relative 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's Avatar
    tanny242 Posts: 1, Reputation: 1
    New Member

    Feb 1, 2009, 12:39 PM

    I don't know what is the difference between air speed and ground speed! like in kn or something
    Stratmando's Avatar
    Stratmando Posts: 11,188, Reputation: 508
    Uber Member

    Feb 1, 2009, 01:14 PM

    Hopefully the 2 above post will explain.
    You compare both at Miles Per Hour OR
    Flying Blue Eagle's Avatar
    Flying Blue Eagle Posts: 2,056, Reputation: 225
    Ultra Member

    Feb 2, 2009, 07:03 PM

    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<
    amit_shukla's Avatar
    amit_shukla Posts: 1, Reputation: 1
    New Member

    Oct 16, 2010, 04:48 AM
    see it like this... wind speed is speed of air with respect to ground and airspeed is speed of aircraft with respect to the wind and ground speed is speed of aircraft with respect to ground... so, ground speed=vector sum of airspeed and wind speed.
    if airspeed=60 kph and there is a tail wind of 40 kph, it means that aircraft is moving through the air with a speed of 60 kph... but the air is also moving in the same direction with a speed of 40 kph... so the aircraft would have to move faster to catch up with the wind and maintain an airspeed of 60 kph, thus increasing its ground speed...
    qadarmunir's Avatar
    qadarmunir Posts: 1, Reputation: 1
    New Member

    Dec 1, 2010, 01:37 PM
    its so simple'
    Airspeed=ground speed (+ --) wind speed
    let suppose air craft speed is 5 km/hr on the ground in the direction of the wind and wind speed is 2 km/hr the result will be
    air speed= 5+2=7 km/hr
    similarly if the air craft is moving in opposite direction of the wind,the result will be
    air speed=5--2=3 km/hr
    simply if the moving body is in the same direction of the wind we should add the wind speed or in opposite direction we should subtract the wind speed.
    DavidDegallier's Avatar
    DavidDegallier Posts: 6, Reputation: 1
    New Member

    Jan 15, 2011, 11:51 AM
    Another way to look at it is: If you were standing still in a 20 mph wind, your ground speed is zero but you do have a wind speed of 20 mph. Technically, an aircraft can take off and fly and not get anywhere fast. An aircraft that flies slowly say at 40 mph flies into a 40 mpg wind and is "still" over the ground. This is one reason why planes parked at an airport need to be tied to the ground. If you're still not confused: air's speed is measured in ground speed but airspeed and ground speed are only equal when the wind vector is zero.

Not your question? Ask your question View similar questions


Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.

Check out some similar questions!

Difference between true air speed and equivalent air speed [ 4 Answers ]

What is the difference between the two and when an aircraft is flying at altitude what is its actual speed

Variable Speed vs. Single Speed Blower [ 1 Answers ]

Questions: Getting 2 new heat pump systems installed. 1.5 ton upstairs and 4 ton downstairs. Decided on Comfortmaker. Heat Load calc performed on sizes. Going 2 stage with variable speed downstairs with Honeywell IQ Pro stat. Was going to go one stage with variable speed upstairs with...

High-speed Cable/low Speed Operation [ 1 Answers ]

I had Time Warner Cable(TWC) Road Runner service(high-speed cable) installed recently on my Panasonic CF-47 Laptop. It turns out that it operates two times SLOWER than Dial-Up!! I have a W98 O/S. The High-speed cable into the computer measures normal(as measured by a super-tech with TWC). After he...

View more questions Search