On Jan 7, 8:34*am, Andy wrote:
On Jan 7, 7:20*am, "HL Falbaum" wrote:



If I read this correctly, the scored first leg distance is unknown until the
first turn is made?

No, while that is true, it is not the point I wished to make.

To understand the issue you need a picture of the task I described
showing the tangent points and the arcs that intersect the start
cylinder. *Since I can't provide that you will need to draw it
yourself.

The point I wished to make is that the area of the start cylinder that
will give full credit for first leg distance is dependent on the
position of the first turn area control fix (the pilot selected turn
point). *Since the position of that control fix is unknown when the
start point is selected, *the pilot takes a risk when starting in some
areas in the front half. *The no risk area of the start cylinder is
not the "front half" but an area that may be considerably smaller than
the "front half". *That no risk area is defined by the area of overlap
between the two arcs drawn from the turn area tangent points.

Note that no start penalty will show on the score sheet, you just lose
distance that you thought was part of your first leg. *This makes it a
hidden penalty and most pilots would not even realize they had lost
points as a result of the chosen start point.

This will be of particular interest to SW pilots that often start out
of the top and needs to be understood by anyone flying at R9 Parowan
unless the proposed rule change is abandoned.

Andy

Okay - you shamed me into doing the math (only one decimal place).

I agree with Andy that the rule creates a potential problem because it
defines the "front half" of the cylinder as the circular arc centered
on the "control fix" in the first turn area (that's the place where
Winscore determines you made the turn) that passes through the center
of the start cylinder.

To visualize this draw two circles on a piece of paper - one has a
radius of 5 units (this is the start cylinder). Draw the second with a
radius of 30 units, just above the first and touching at the edge.
Your diagram now looks like a simple drawing of a soccer ball sitting
on top of a baseball. This is the worst case scenario - the biggest
possible first turn area (30 mi) sitting as close as possible to the
start cylinder (somebody check me that there isn't some minimum first
leg distance in the rules that is greater than 35 miles).

Now imagine two pilots - one pilot who thinks conditions look best to
the extreme right edge of the first turn area and another who thinks
the extreme left edge of the turn area looks best. Each pilot
contemplates what their "front half" of the start cylinder will be if
they fly as they intend to the right/left sides of the turn area. The
first pilot figures on a "front half" that is rotated to the right by
some number of degrees to reflect his expected rightward courseline.
The second pilot figures on a "front half" that is rotated to the left
by an equivalent angle. Based on strategy (or just where the lift is)
each pilot takes a start from the far corner of their respective semi
circles (not exactly a semicircle since it's defined by an arc, but I
don't have a word for that shape). The first pilot to the right and
the second pilot to the left.

Each pilot heads out on course, but a few miles out each notices
something that makes them change their plan (a cu popping, a fast-
climbing competitor, whatever). Each now decides to go the the
opposite side of the first turn area from their initial plan - and
does so. They fly the course, land and turn in their flight logs. When
the scores come back they find themselves scored for less distance
than they thought. They go to the scorer who looks at the logs and
discovers that when each pilot changed their first turn point they
rotated the first leg course line and thereby rotated the allowed
"front half" of the start cylinder. For scoring purposes each pilot
started miles outside their respective "front half" and had their
first leg distance reduced by that amount.

So now the math part:

In the worst case scenario described above it is possible for the
"front half" of the start cylinder to be rotated plus or minus 51.3
degrees to the left or right of the line between the center of the
start cylinder and the center of the first turn area. This means that
if you are either of the pilots in the above example you will be
scored for 5 miles less than you actually flew.

So how might pilots respond to this? One possibility it that pilots
might play it totally safe and start out of the part of the cylinder
where all possible first turnpoint "fixes" can be reached without
penalty. If you do the math this is an arc with an angle of 77.3
degrees centered on the line from the center of the start cylinder to
the center of the first turn area. This "safe arc" has a length of 6.7
miles rather than 31.4 miles for a full "front half" of the cylinder.
The other possibility is that pilots who don't start in this "safe
arc" will feel compelled to press on to their initially planned
turnpoint out of concern that they will be docked miles if they
change. For some flights you may need to have Winscore recalculate the
control fix in the first turn to trade off distance lost at the start
versus distance made at the turn - that would be funky.

I realize this is the worst case scenario and that the first turn area
may likely be a bit further away than 35 miles or smaller than 30
miles in radius - particularly in the west. This would make the "safe
arc" for starting bigger than I describe.The big issue in my mind,
though, is that it is impossible to know ahead of time what is the
allowable start half-cylinder for any flight and therefore pilots will
tend to funnel back toward the front edge of the cylinder to be safe
and to keep their options open, the opposite of what "start anywhere"
is intended to achieve.

Also, I am not sure that this is a rule change that solves a problem
that exists in practice. I presume the thing the RC wants to avoid is
pilots starting out the top of the back of the cylinder and bombing
through start gaggles. I'm not saying it can't happen, I just haven't
seen it.

I'm sure that was clear as mud.

9B