Metric Soaring

Clearly metric is a superior system for most expressions
of measurement, but it seems surprisingly inefficient
for flying (especially soaring) in it's current form,
which brings me to my question(s).
Why do metric variometers read in m/s, instead of kph
when the metric airspeed is in kph? Would it not make
more sense to use kph on the vario too so quick mental
L/D calculations could be done (for those who do not
use a flight computer etc to think for them)?
After doing a little homework, I figured out a 5 m/s
is 18kph (1m/s is 3.6 kph). If I used metric to fly
(I'm just plane knots) I would much rather have a vario
that went up/down to 20kph, and was hash marked on
single kilometers with numbers every 5th hash mark
for the main vario.
For a weak lift unit it would be hash marked for 1/5
kilometers but numbered every whole kilometer up/down
to 5kph.
Strong lift versions would be up/down to 30 or 40kph,
hashed every second kilometer and numbered every 5th
hash mark...Just a thought, but makes me curious.

Paul Hanson
"Do the usual, unusually well"--Len Niemi

Paul Hanson wrote:
Why do metric variometers read in m/s, instead of kph
when the metric airspeed is in kph? Would it not make
more sense to use kph on the vario too so quick mental
L/D calculations could be done (for those who do not
use a flight computer etc to think for them)?

Well, altitude is usually measured in meters, and meters/second is the
preferred SI unit for speed. Which does bring up a related mystery.
When I was first flying gliders in the northeast US from the late 60s
through the mid 70s, pretty much all of the ASIs were in MPH and the
varios were in FPM. When I restarted flying gliders in California
during the late 80s, pretty much all of the ASIs and varios were in
knots. Was this a regional thing, or did some sort of cataclysmic shift
take place while I was off doing other silly things?

Marc

Because 1 or 2 km/hour is really slow, but 1 or 2 meters per second is
not. (Imagine the ASI in meters/second.)

At 00:18 15 September 2007, Marc Ramsey wrote:
Paul Hanson wrote:
Why do metric variometers read in m/s, instead of
kph
when the metric airspeed is in kph? Would it not make
more sense to use kph on the vario too so quick mental
L/D calculations could be done (for those who do not
use a flight computer etc to think for them)?

Well, altitude is usually measured in meters, and meters/second
is the
preferred SI unit for speed. Which does bring up a
related mystery.
When I was first flying gliders in the northeast US
from the late 60s
through the mid 70s, pretty much all of the ASIs were
in MPH and the
varios were in FPM. When I restarted flying gliders
in California
during the late 80s, pretty much all of the ASIs and
varios were in
knots. Was this a regional thing, or did some sort
of cataclysmic shift
take place while I was off doing other silly things?

Marc

Not too cataclysmic. Somebody was smart enough along
the way to realize that 100fpm was almost exactly 1
knot. Plus, since one degree of latitude was a nautical
mile it only made sense to use knots for vertical and
horizontal motion to reduce cockpit workload in the
days before the electronic flight computer (I learned
some of this from a Derek Pigot book). It was actually
a worse situation than that here in the US, before
the fpm/mph days, when most varios here were expressed
in fps and airspeeds in mph which made for even more
math that was very avoidable (there are still a lot
of archaic instruments used, reading in silly mph and
fpm and even fps; old habits die hard) This is why
I am so baffled at m/s vs kph in a metric cockpit.
To get L/D you need to multiply your m/s vertical speed
by 3.6 to get kph before you can divide it into your
airspeed. The altitude thing is no problem whether
it is expressed in m or km, as that is a mere decimal
place switch with no real math involved, so turning
that into useful range on a map is no problem-once
you have your L/D figured.
Since m/s is the SI for speed, than why kph on the
airspeed? I'm not hung up on m/s vs kph, just the fact
that the ASI and vario should be in the same units
for quick number crunching during X/C. A m/s airspeed
would serve the same purpose with current metric varios
that kph varios would serve with current metric airspeeds.
Altimeters can stay in m without affecting workload.

Paul Hanson
"Do the usual, unusually well"--Len Niemi

Actually, I think it's one minute of latitude equals a nautical mile - works
great at a chart table with dividers but not much use in a glider cockpit.

I don't think vario units make much difference - up is good, more up is
better on any vario. Most varios aren't all that accurate anyway. Airspeed
units are more critical but most pilots just use the colored arcs and the
STF audio from the vario.

I've never used a vario in knots and an airspeed in knots to figure the d/h
ratio. The electronic gadgets do that if you are interested.

Now altimeters in meters are a pain. With 3200' per rev on the big hand how
do you know it isn't stuck?

BD


"Paul Hanson" wrote in message
...
At 00:18 15 September 2007, Marc Ramsey wrote:
Paul Hanson wrote:
Why do metric variometers read in m/s, instead of
kph
when the metric airspeed is in kph? Would it not make
more sense to use kph on the vario too so quick mental
L/D calculations could be done (for those who do not
use a flight computer etc to think for them)?

Well, altitude is usually measured in meters, and meters/second
is the
preferred SI unit for speed. Which does bring up a
related mystery.
When I was first flying gliders in the northeast US
from the late 60s
through the mid 70s, pretty much all of the ASIs were
in MPH and the
varios were in FPM. When I restarted flying gliders
in California
during the late 80s, pretty much all of the ASIs and
varios were in
knots. Was this a regional thing, or did some sort
of cataclysmic shift
take place while I was off doing other silly things?

Marc

Not too cataclysmic. Somebody was smart enough along
the way to realize that 100fpm was almost exactly 1
knot. Plus, since one degree of latitude was a nautical
mile it only made sense to use knots for vertical and
horizontal motion to reduce cockpit workload in the
days before the electronic flight computer (I learned
some of this from a Derek Pigot book). It was actually
a worse situation than that here in the US, before
the fpm/mph days, when most varios here were expressed
in fps and airspeeds in mph which made for even more
math that was very avoidable (there are still a lot
of archaic instruments used, reading in silly mph and
fpm and even fps; old habits die hard) This is why
I am so baffled at m/s vs kph in a metric cockpit.
To get L/D you need to multiply your m/s vertical speed
by 3.6 to get kph before you can divide it into your
airspeed. The altitude thing is no problem whether
it is expressed in m or km, as that is a mere decimal
place switch with no real math involved, so turning
that into useful range on a map is no problem-once
you have your L/D figured.
Since m/s is the SI for speed, than why kph on the
airspeed? I'm not hung up on m/s vs kph, just the fact
that the ASI and vario should be in the same units
for quick number crunching during X/C. A m/s airspeed
would serve the same purpose with current metric varios
that kph varios would serve with current metric airspeeds.
Altimeters can stay in m without affecting workload.

Paul Hanson
"Do the usual, unusually well"--Len Niemi

On Sep 14, 8:27 pm, "Bill Daniels" bildan@comcast-dot-net wrote:
Actually, I think it's one minute of latitude equals a nautical mile - works
great at a chart table with dividers but not much use in a glider cockpit.

I would use my thumb and index finger on a sectional chart to measure
distance all the time. Good enough considering the uncertainty of the
airmass we fly in.

Using NM and feet altitude also makes the E-6B wizz wheel into an
instant glide computer. Just put altitude vs. distance and the arrow
points to the glide ratio. Do this every few miles and you can see a
trend - constant or decreasing and you can probably make it.

Also, 20:1 and 30:1 are useful numbers for most sailplanes. An ASK-21
will most likely do 20:1 and an ASW-20 will do 30:1 (though I used to
do 20:1 when over rough terrain or expecting strong sink). So, take
the distance in NM and multiply by 200 and you have 30:1. Multiply by
300 and you have 20:1. Granted, this would be just as easy in metric
units, but not the map measurements.

Someday, I just might have a complete electrical failure... and it's
nice to have a few mental tricks available.

-Tom

I have been really distressed since returning to Alaska from St.
Auban a few years ago when I had to give up my very easy metric 20/1
glide calculator system for 1/250,000 maps, i.e., my right hand with
four fingers, and a metric altimeter.

Life should be so easy here. Here's why:

A hand's width, just above the knuckles, is 20k on my marked up French
road map commonly used for soaring in the Sud Alpes. So at 20/1, you
need 1,000 meters to glide your hand's width across the map. Two
fingers on the map to a safety field requires 500 meters plus pattern
entry height which I had already marked on my map. All I had to do
was to count my fingers to the landing field, multiply by 250, and
add the pattern entry height to know whether I had to buy a new glider
or not.

It doesn't get much simpler than that which is fortunate for me
because I can't do much more complicated calculations in my head,
especially when I am stressing because I am low and lost in the
mountains in a foreign country where the only people who speak worse
French than I do are my fellow Alaskans Jeff Banks and Ed Kornfield
who also flew from St. Auban. No GPS, PDAs, or complicated glide
calculators (formerly known as prayer wheels in the old days of
circular slide rules), just lay your hand on the map, count your
fingers, and add.

One note on French altimeters: In addition to being marked in meters,
the French, rather sensibly when you think about it, have the -0- mark
on the altimeter on the bottom of the dial and you go up from there.

Pete Brown
Anchorage


Also, 20:1 and 30:1 are useful numbers for most sailplanes. An ASK-21
will most likely do 20:1 and an ASW-20 will do 30:1 (though I used to
do 20:1 when over rough terrain or expecting strong sink). So, take
the distance in NM and multiply by 200 and you have 30:1. Multiply by
300 and you have 20:1. Granted, this would be just as easy in metric
units, but not the map measurements.

Someday, I just might have a complete electrical failure... and it's
nice to have a few mental tricks available.

-Tom

Well, actually, it is!

I was taught this trick years ago----glad to see it works in "metricland"
also.

One finger width on a USA Sectional Chart 1:500,000 is (approximately) 5 NM
One Nautical Mile is (approximately) 6000 ft

So--at 30:1 (200 ft/mi), one finger is about 1000 ft required.
At 20:1(300 ft/mi), one finger is about 1500 ft required.

Add in pattern altitude, and there you are!

Hartley Falbaum
USA "KF"


wrote in message
ups.com...
I have been really distressed since returning to Alaska from St.
Auban a few years ago when I had to give up my very easy metric 20/1
glide calculator system for 1/250,000 maps, i.e., my right hand with
four fingers, and a metric altimeter.

Life should be so easy here. Here's why:

On Sep 14, 9:27?pm, "Bill Daniels" bildan@comcast-dot-net wrote:
Actually, I think it's one minute of latitude equals a nautical mile - works
great at a chart table with dividers but not much use in a glider cockpit.



Bill, It's one minute of LONGATUDE that equals a nautical mile.
minutes of latitude vary in spacing depending how far north or south
they go. Just got my Navigator wings, so I guess I can correct
you. :-)

-EX

Yikes! What are you going to be navigating?

Go north or south one nautical mile, and you have moved a minute of
latitude.

Move a minute of longitude, and you have moved east or west, and the
distance varies how far north or south you are.




Mitch wrote:
On Sep 14, 9:27?pm, "Bill Daniels" bildan@comcast-dot-net wrote:
Actually, I think it's one minute of latitude equals a nautical mile - works
great at a chart table with dividers but not much use in a glider cockpit.



Bill, It's one minute of LONGATUDE that equals a nautical mile.
minutes of latitude vary in spacing depending how far north or south
they go. Just got my Navigator wings, so I guess I can correct
you. :-)

-EX