What is the minimum average distance flown needed for full
distance validity?

By setting the Distance Validity to 1 we can see how far pilots have to fly to
make for full distance validity for different values of nominal distance.

Distance Validity Ratio := 2 * Nflyover * (AVGover - Dmin)/(Nfly*((1 + Gnom/100)
* (Dnom-Dmin) + (Gnom/100 * (Dmax-Dnom)))) = 1

AVGover = the average distance (total) flown by the pilots who flew over the
minimum distance

Nflyover = the number of pilots who flew over the minimum distance

AVGover = Nfly/Nflyover * (((1 + Gnom/100) * (Dnom-Dmin) + (Gnom/100 * (Dmax-Dnom)))/2)
+ Dmin

For example:

Given the Dmax = 100 km, Dmin = 5 km, Gnom = 20 the line above gives the
relationship between the meet director's choice of nominal distance and the
average distance required for full validity. At the low end the required average
distance is greater than the nominal distance. At the higher end the required
distance is less. (I assume that all pilots fly longer than the minimum
distance.)

The meet director should be setting the Nominal Distance knowing how far he
expects pilots on average to fly during the competition.

Given the Dmax = 100 km, Dmin = 5 km, Dnom = 60 km, the chart below gives the
relationship between the meet director's choice of percentage of pilots at goal
and the required average distance flown for full validity:

Full Distance Validity also depends on what percentage of the pilots fly further
than the minimum distance. Given the Dmax = 100 km, Dmin = 5 km, Dnom = 60 km,
and Gnom = 20, we get the following relationship:

These charts are restricted by the assumption of 100 km maximum distance. I'll
look further at the relationships shown here when we have a much bigger task in
the next article.