90 degrees off topic...

On Tuesday, March 6, 2001 at 4:34:39 AM UTC-8, Jean Richard wrote:
Kirk Stant a écrit :

Why? While I may agree that metric units are OK for ground use, in the air
and on the sea the Nautical mile (one minute of latitude) is the preferred
unit of distance, easily measured on any chart, and is likely to remain so
for the foreseeable future. Therefore, the Knot is the most useful unit of
speed. As far as altitude, feet are just as useful as meters, why change?

I've been flying in Europe a few times and really appreciate to have
altimeter in metre and not in feet since it's a lot easier to make
glide calculations.

I would like to get rid of our feet calibrated altimeter (I'm living
and usually flying in North America...).

As so far distance is concerned on a chart, we always use metres, and
it's also a lot easier since you just take any rule to mesure distance
and convert it from centimetres to kilometres.

For soaring, using Knots for airspeed and climb is nicely consistent and
makes for easy guesstimating of instantaneous glide angle.

No ! Because your airspeed is not indicating ground speed, but airspeed.

Here, we are sometimes happy to have GPS since they all work in SI.

And since a
nautical mile is just over 6000' (6080'), one can easily use multiples of
nautical miles per 1000' for mental figuring glide distances: 36/1 is 6
nm/1000', 30/1 is 5 nm/1000', 24/1 is 4 nm/1000', and so on. Try doing
any of that with Kph, Meters, and M/Sec!

Distance in km and altitude in metres. That's all we need. Airspeed and
vario are not used for gliding calculation, just for speed to fly -
the Mac Cready (or any more sophisticated device) do the job for you.

I'm not a Europhobe

SI units is not only for Europe. It's the official unit system in all
America, except USA.

(I'm half French, and have lived in Europe many years)
but I do think that, for aviation at least, the archaic foot, nautical mile,
and Knot should remain in place indefinitely.

At first, ICAO want to discard anything except SI. But due to difficulties
in conversion (and cost), ICAO went for a « temporary » exception chart to
included some non SI units. The MPH are no more accepted (here in Canada,
selling a new airplane with MPH airspeed indicator is not legal).

Now if we could only get US
soaring pilots to stop using MPH and statute miles for speeds and distances,
instead of the Knots and NM they use in-flight, we would be getting
somewhere!

SI is easier... Weather observation (METAR) in USA are mixing knots (wind)
with statute miles (visibility), and feet (I don't know if Imperial feet
and US feet are the same), inches of mercury. What a mess !

It's bad enough having to figure if you have enough NM to make
your 500K flight, but then you have to convert that into Statute miles for
club bragging rights!

FAI distance badges are in kilometres, nothing else ;-))

Vive les pieds! A bas les Metres (une vrai connerie!)

J'ai toujours préféré les maîtres aux pieds ;-))))

Jean

International aviation standards use feet and English. All of my charts reference altitude in feet, as well as FARs. Can't speak for your European charts, however. The FAA will not be receptive to you busting airspace because your altimeter is in meters.

I have very rarely found it necessary to compute a glide angle while flying.. I always used X NM per thousand feet (X is directly related to achieved glide angle; I use 7 NM for may ASH31, which 73% of best L/D). And I still double-check my LX9000 using this same method. I just see how much distance closer I am at each 1000 ft mark. I get an instantaneous glide angle from my LX9000, but this varies so much that it is not of much value.

Tom