Here's the solution to the problem that someone might be tempted to
dive for the base of the finish cylinder and do a radical pull-up, as
well as the problem that someone might try to thermal at 300' to get up
to 500' and save himself the rolling-finish penalty:

There is a donut of airspace, from 1 mile radius to (say) 4 miles
radius, with top at 500 feet (or finish cylinder base, if higher). This
is forbidden airspace, marked in the sua file as such. One fix in that
airspace, and you've landed out. (Or, if you feel that's too much, it
gets you a 100 point penalty, plus any rolling finish penalty or time
addition.) Essentially, we create an airport located in a 1 mile radius
valley, surrounded by a plateu at 500 feet.

Now the optimum thing to do for a pilot who cares even zero about his
own safety is to fly about 90 kts (regular glide speed) to about the 2
mile radius and 501 feet, then let speed bleed off to the average speed
for the flight at the 1 mile mark. Of course, sensible people will
just fly 90 kts to the 550' 1 mile point, with trivial loss of points.

(It's not efficient to end up as slow as possible at the 1 mile mark.
To see why, imagine you could fly at 0 airspeed. Taking 10 minutes to
go the last 100 feet would not make sense. If you flew 60 mph average
for the flight, flying level at 59 mph slows you down, while flying
level at 61 mph increases your average speed. Thus, you want to cross
the line at the average speed for the flight, 60 mph in this case. 5-10
kts extra cost hundredths of a point.)

There is no incentive for low-altitude thermaling just outside the
cylinder. Once you're below 500 feet (or 1000, or whatever the top of
the donut) you landed out so you might as well glide home. (If it's 100
points plus the rolling finish penalty, you just got the rolling finish
penalty, so again you might as well stop screwing around and go land.)
If you're 5 miles out and you can't make it over the donut (about 1200
feet is the decision height here), you have every incentive to stop;
either thermal at a decent altitude or find a decent landing place.
It's just like not being able to cross the final ridge into the
airport.

There is no need for a rules change to do this. CDs may now designate
any airspace they want to as off limits. Just put the donut in the sua
file. Any CD or contest manager who wants to ensure really safe
finishes can put this into place now.

The donut can also be used with a conventional finish line. This will
ensure that pilots arrive at the airport with plenty of energy, or
already committed to rolling.

John Cochrane
BB