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I'm tracking a flight--what does ground speed 390 KTS mean?

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candy Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:24 PM
Original message
I'm tracking a flight--what does ground speed 390 KTS mean?
Just curious!
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Catch22Dem Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:26 PM
Response to Original message
1. 390 knots = approx. 450 mph
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candy Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:30 PM
Response to Reply #1
6. Thanks
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DS1 Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:27 PM
Response to Original message
2. knots
449 of em, give or take
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candy Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:31 PM
Response to Reply #2
8. Thanks
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candy Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:39 PM
Response to Reply #2
11. thanks
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LastDemocratInSC Donating Member (580 posts) Send PM | Profile | Ignore Thu Nov-25-04 10:27 PM
Response to Original message
3. 390 knots ground speed, may be different from air speed
It means that the aircraft is traveling at 390 knots over the ground. If flying into a headwind the airspeed may be greater - if flying with a tailwind the airspeed may be less.

A knot is 1.17 mph, 1 mph is .622 knot.
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candy Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:31 PM
Response to Reply #3
9. Thanks
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karlrschneider Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 11:07 PM
Response to Reply #3
19. Back in the early 70s when I got my first flying job, I had a groundspeed
of over 380 Kt in a plane (Cessna 310) that did well to achieve 190 airspeed...from somewhere in Ohio to Virginia, AFAIR...the DME was going berserk. Jetstream was way low that day. :D
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kdmorris Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:27 PM
Response to Original message
4. I think KTS is knots
1 KTS = 1.17 MPH
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candy Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:32 PM
Response to Reply #4
10. Thanks
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mhr Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:28 PM
Response to Original message
5. 390 Nautical Miles Per Hour = 450 Miles Per Hour
eom
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candy Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:41 PM
Response to Reply #5
13. Thanks
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Silverhair Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:31 PM
Response to Original message
7. It means
That you are moving, relative to the earths surface, at 390 nautical miles per hour. A nautical mile is used for aircraft as it is equal to one minute of latitude, which makes for easier calculations.

In ordinary terms, a nautical mile per hour, (called a knot. Never, ever call knots per hour) is 6,080 feet. That is about 1.15151 miles, or about 450 miles per hour.
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A HERETIC I AM Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:40 PM
Response to Reply #7
12. I had always thought a Nautical mile was 2000 yards.......
or 6000 feet, which, if i am not mistaken, is the distance to the horizon when viewed from sea level.

Ever heard this? Or am I laboring under a flawed understanding of the facts?
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Pepperbelly Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:42 PM
Response to Reply #12
15. In the Navy, 2000 yards was a nautical mile.
Exactly.
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Silverhair Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:47 PM
Response to Reply #12
16. Actual figure is 6,076 feet. Link included in text.
http://people.howstuffworks.com/question79.htm

Sorry about the 6,080 figure. I was a bit off on that one too, and I spent 5 years in the US Navy, and was a navigation officer. (Red face from embarrassment)
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Silverhair Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:48 PM
Response to Reply #16
18. Embarrassed from wrong figure, NOT from Naval Service. Proud of that. NT
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billyoc Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 11:16 PM
Response to Reply #18
20. Navy here too, Merchant Marine after that
different values have been used. The value 1852 meters (6076.1 ft.) has been adopted internationally.
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candy Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:42 PM
Response to Reply #7
14. Thanks
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karlrschneider Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 10:47 PM
Response to Original message
17. It's 448.5 MPH to be exact. 1 Kt (Nautical Mile) is 1.15 Statute miles
Edited on Thu Nov-25-04 11:04 PM by karlrschneider
Us pilots have to deal with this minutia often. :D
edit: technically, it's one arc minute of the equatorial circumference (which we obviously don't even know precisely) that according to the best guess is actually 1.15756 statute miles...which derives from ancient measurements that relied on the length of the foot of some kings) :eyes:
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Festivito Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Nov-25-04 11:56 PM
Response to Original message
21. I my defense , I took a nap today.
1.15 or 1.152 miles per nautical mile.

The diameter of the earth is too oft said to be 8000 miles. Commercial planes often travel five miles up making the diameter 8010 giving that 1.17 figure some people use.

A closer diameter comes from the definition of a meter as one-ten-thousandth the distance of 45 degrees of latitude which extrapolates the worlds circumfrence to an exacting 80,000 km. So,

80,000
/2 /pi diameter in km
*1000 dia in m
*100 dia in cm
/2.54 dia in inches (inexplicably exact)
/12 dia in feet
/5280 dia in miles
7911.54373915808358033503158417414 miles of earth diameter
*pi circumfrence in miles
/360 miles per degree
/60 miles per minute of a degree, i.e. per nautical mile
1.15068739303209994373598923030244
For the fun of it:
*5280
6075.62943520948770292602313599689 feet in a nautical mile...
... despite the 6000 ruling used in the military.

Add 10 miles to the 7911 figure to get the 1.152 in case the plane is measuring its air speed five miles up while you'd use ground distances between cities. But, speed by any other name would not be so fast...

Knots used to measure speed at sea using the number of equidistant knots that would freely drop from the stern of a ship divided by the time they took -- all at sea level back then.

I imagine your friend's plane has arrived by now.
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ladjf Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Nov-26-04 04:23 AM
Response to Original message
22. The plane is covering ground at 390 knots. The number is
used by pilots to predict flight time between points on the ground. It factors in the wind component.
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