Alternative to 500-foot/1-mile rule

So here's a different idea:

What if, in instances where we are using a 1 mile cylinder
for the finish, instead of putting in a hard deck of
500', we make it so the scoring program can calculate
TOTAL ENERGY for each glider at the one mile point
(this should be relatively easy to do). The idea would
be for each sailplane to have at least 500' of EQUIVALENT
ALTITUDE at 1 mile. That is, take actual AGL altitude
and add the equivalent altitude that the glider would
have if it's kinetic energy were converted to altitude
(at say 60 knots).

The CD would then have the option to assess penalties
proportional to the difference between 500' and the
actual equivalent altitude for a 'low energy finish'.

Before you all bust my chops over pilot workload calculating
a theoretical energy number, consider what this means
in terms of actual speeds and altitudes.

My ship, on a 10 knot glide to 50' at the center of
the cylinder, would be at 284' doing 139 knots at 1
mile and would have a total energy equivalent altitude
of 984' - nearly twice the 500' limit.

On a 5 knot glide you would be at 214' doing 111 knots,
with a total energy equivalent altitude of 597'.

On a 3 knot glide you'd be doing 97 knots at 187' and
your total energy altitude would be 443' - 57' into
the penalty zone.

On a best L/D glide you'd be at 162' doing 70 knots
and total energy equivalent altitude of 272' - 228'
into the penalty zone.

I don't know about you all, but I'm generally above
the 5-knot altitude and speed at 1 mile on any final
glide that I'd consider reasonable - so I don't think
anyone is going to need to do any math in the cockpit.
At the same time, by measuring total energy, we're
not fixed on a specific altitude irrespective of speed
(a problem with the 500' rule). It also gives the CD
the option to assess a penalty for 'low energy finish'
or not - depending on circumstances. The calculation
off the flight log is simply a guide.

The main advantage is that pilots who want to trade
excess altitude for speed in the last few miles wouldn't
have to go 'heads down' to make sure they don't his
the 500' finish barrier. In fact, the only pilots facing
a penalty would be those who are getting into very
flat final glides (Mc = 3.5 with 50' of buffer).
The chance of dipping into the penalty zone shold reduce
the incentive to press on at low altitude.

There would be no 1-mile 'barrier' to get over - as
there is today and because it is a total energy measure,
the 1 mile heroic pullup to get to 500’ wouldn't happen,
because it wouldn’t help. Also, it would preserve the
incentive for pilots to stick with that last weak thermal
out on course to get some safety margin rather then
heading home on a marginal glide, since even a weak
thermal would reduce potential penalty points faster
than it loses speed points.

It also preserves getting speed points (without penalty)
for rolling finishes – so long as you have enough energy
at 1-mile.

You can adjust the total energy altitude limit and
the number of points per foot below the limit, though
500’ and 1:1 seem like a good start to me.

Thoughts, comments, flames?

9B

In article ,
Andy Blackburn wrote:

What if, in instances where we are using a 1 mile cylinder
for the finish, instead of putting in a hard deck of
500', we make it so the scoring program can calculate
TOTAL ENERGY for each glider at the one mile point
(this should be relatively easy to do). The idea would
be for each sailplane to have at least 500' of EQUIVALENT
ALTITUDE at 1 mile. That is, take actual AGL altitude
and add the equivalent altitude that the glider would
have if it's kinetic energy were converted to altitude
(at say 60 knots).

I agree with the idea, but the fly in the ointment is wind -- the
analysis computer won't know what the wind is, so it can only know your
groundspeed not your airspeed. It will thus let you get away with a
lower airspeed if you're going downwind, while you'll need a higher
airspeed to satisfy it if you're going upwind.

Fortunately, these errors are in the sensible direction, but the
magnitudes of them may or may not be sensible.

-- Bruce

I does make a difference - 25 knots could bias the
apparent energy by 250'. So you would either have to
estimate wind from the traces based on thermal drift,
and/or make it part of the CD's discretion.

You are correct that a tailwind both raises the apparent
energy as measured by GPS and reduces the altitude
you need to get home, the first effect is bigger than
the first so they don't totally offset.

9B

At 03:30 06 October 2003, Bruce Hoult wrote:
In article ,
Andy Blackburn wrote:

What if, in instances where we are using a 1 mile
cylinder
for the finish, instead of putting in a hard deck
of
500', we make it so the scoring program can calculate
TOTAL ENERGY for each glider at the one mile point
(this should be relatively easy to do). The idea would
be for each sailplane to have at least 500' of EQUIVALENT
ALTITUDE at 1 mile. That is, take actual AGL altitude
and add the equivalent altitude that the glider would
have if it's kinetic energy were converted to altitude
(at say 60 knots).

I agree with the idea, but the fly in the ointment
is wind -- the
analysis computer won't know what the wind is, so it
can only know your
groundspeed not your airspeed. It will thus let you
get away with a
lower airspeed if you're going downwind, while you'll
need a higher
airspeed to satisfy it if you're going upwind.

Fortunately, these errors are in the sensible direction,
but the
magnitudes of them may or may not be sensible.

-- Bruce