Well, it was meant to be a humorous play on words, Andrew :-)
There is no point in declaring the maximum groundspeed of an aircraft
because it varies with the strength of the wind. If I fly at 560
knots true airspeed (TAS) into a wind of 100kts my groundspeed will
be 460kts. If I fly with that wind "up my chuff" it will be 660kts.
Now the speed of sound at sea level is 660kts in a standard
atmosphere, but having a groundspeed of 660kts does not mean that I
am supersonic.
As an example, I once flew a Tornado GR1 from RAF Marham in Norfolk
to RAF Laarbruch in Germany. With a jetstream from the southwest at
our cruising altitude of around 30,000ft, we had a groundspeed of
nearly 1,000kts (according to the nav kit) but we were flying
subsonic, at around M0.85.
I suppose "effective" speed depends on what you are trying to
achieve. If you are trying to get somewhere, the groundspeed is your
effective speed. But if you are trying to catch another aircraft to
wreak destruction on it, TAS or Mach Number is your effective speed.
You will both be affected equally by the wind and your groundspeeds
are immaterial. Finally, if you are trying to make your best climb
angle, you will fly at the recommended indicated airspeed or Mach
Number to achieve that goal.
Does that make sense? :-)
Chris
~~ >-)-
C M I Barker
Cambridgeshire, Great Britain.
+44 (0)7092 251126
www.threeshoes.net
homepage.mac.com/zuiko
On 10 Mar 2007, at 08:46, Andrew Fildes wrote:
>
> I hope that's a joke - I have enough trouble with reality as it is!
> If the earth is moving with the wind (or even my wind, being a
> certified old fart) then I'm in serious trouble.
> Surely groundspeed is effective speed?
> Andrew Fildes
> afildes@xxxxxxxxxxxxx
>
>
>
> On 10/03/2007, at 6:07 PM, Chris Barker wrote:
>
>> Groundspeed is immaterial, in
>> general terms, because it changes with the wind ... ;-)
>
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