Mechanical Vario

"Dan G" wrote in message
ups.com...
On Sep 28, 11:44 pm, Bob Whelan
wrote:
Personally, I think the Gospel of Simplicity ought to be preached more,
because so much of soaring does not REQUIRE the latest in bells and
whistles be present in order for fledglings to begin spreading their
wings in personally gratifying and safe ways. Flight (in any form)
costs more than remaining groundbound. Soaring flight as a niche
certainly isn't cheap (in time or money or mental effort required), and
any barriers (real or imagined) to achieving it are precisely that:
barriers. I don't think soaring participants should be promoting Mark
CXXIV widgets as a universal good, or worse, as necessary, to everyone
getting into the sport.

Couldn't agree more - hence my comment that technology peaked with the
B40 :-).

I'm not a big fan of slavishly following the vario when cruising -
there's a lot of evidence that there's little to be gained in terms of
overall XC speed. In fact there's a very good chance that by the time
you've slowed up, you're in sink, and by the time you've accelerated,
you're in lift. A glider doing 70 knots is travelling at ~30 m/s -
allow for the seconds of the vario reacting, the pilot reacting, and
the glider responding to your control inputs and you'll have travelled
an easy 100 m - that is, you're effectively reacting to air that's 100
m behind you. Which probably won't be doing the same thing as the air
you're now in.

This is a testable thesis.

Careful study of OLC logs show those with the best flights do indeed indulge
in 'dolphin flying'. Of course, not all zooms are successful, but on
average, they are. Successful 'dolphin flying' requires several things.
One, the thermals must be wide enough. Two, the glider must have good
penetration and three, the pilot must be using relatively high interthermal
airspeeds. (You can't zoom from a low airspeed.)

If you have SeeYou, set it up so there are four windows - three of equal
size on the right half of the screen stacked one above the other. On the
left half display the map view with the trace color set to vertical speed.
Set the top right window to a graph of true airspeed (IAS would be better
but it's not available). Set the middle right window to vertical speed and
set the bottom right window to altitude. Expand the time axis of the three
right windows to the maximum. Now, save this "desktop" so you don't have
set it up again - then animate the flight log.

Those pilots who are 'dolphin flying' will show a sharp reduction in speed
as lift is encountered and a jump of several hundred feet in altitude. If
the zoom is successful, the altitude trace will show a resumption of the
glide displaced upward from a estimated continuation of the pre thermal
encounter trace. In the statistical analysis, the zoomers will show D:h
ratios in the hundreds for their straight glides. Those pilot not zooming
in lift will show D:h values around their best L/D. Dolphin flying clearly
works, but you have to be good at it. The best pilots are really good at
it.


What's much more important in terms of XC speed is climbing fast - and
to do that you need an accurate, well set-up vario. Mechanicals suck
on that score, and as Mike says, they often take the fancy kit with
them unless they've been set up by an expert.

No arguement. The best climbers easily win the day. It's amazing to see
OLC traces on SeeYou where the vertical speed trace shows a sine wave
matching the circle time. This clearly shows the pilot is not centered in
the thermal. The best pilots will show an average climb rate 2-3 knots
better than the average pilot on the same day. The pilot who are good at
zooms are also good at selecting and centering thermals - often on the first
turn.


BTW, on the gust issue, there is another solution (though not nearly
as elegant as the rotating TE probe) - accelerometers. The Vega by
Triadis uses them for gust filtering, but I've not heard of any pilot
reports.

In secret laboratories around the world they are working on the dreaded
"Inertial Variometer" that will change everything.

Bill Daniels

Bill, are you seeing the effect of "dolphin" flying, or just following
the lines of energy (or, avoiding sink). I try real hard to avoid the
classic "pull hard in lif" type of dolphin flying, since in my
experience it slows me down (from comparison flying); OTOH, I try real
hard to look for and exploit lift lines, and gently vary speeds to
match the trend of the airmass. Doing this, I consistently better my
polar's L/D for the speed being flown.

Of course, this is semantics - whatever technique being used, it is a
skill that takes knowledge, practice, and good instruments.

And the fast pilots usually have all three!

Kirk
66

I think that if the airspeed is reduced by 40 knots or so in, say, 20
seconds, that's a zoom. I often see a quicker speed reduction than that. I
would agree than smooth control inputs are better. Timing of the airspeed
changes is more important than the amount.

The key as to whether it worked or not is the barogram trace. If the
downward trend of the glide is displaced upward at the zoom so a new trend
starts at the top of the zoom, there was a net gain. If the thermal was too
narrow or was followed by heavy sink, the barogram trace will just show a
spike with no change in the trend - just a loss in average speed due to the
slowing.

A couple of pilots who seem to be the masters of the "Long Glide" are Kevin
Wyatt and Gary Ittner. You will notice that their airspeed trace is almost
an exact inverse of the vario trace. i.e. vario up, arispeed down and vario
down airspeed up.

On the other hand you will see pilots where there is only a weak correlation
between airspeed and vario. These folks seldom get more than the published
L/D.

Bill Daniels


wrote in message
oups.com...
Bill, are you seeing the effect of "dolphin" flying, or just following
the lines of energy (or, avoiding sink). I try real hard to avoid the
classic "pull hard in lif" type of dolphin flying, since in my
experience it slows me down (from comparison flying); OTOH, I try real
hard to look for and exploit lift lines, and gently vary speeds to
match the trend of the airmass. Doing this, I consistently better my
polar's L/D for the speed being flown.

Of course, this is semantics - whatever technique being used, it is a
skill that takes knowledge, practice, and good instruments.

And the fast pilots usually have all three!

Kirk
66