The 11 best things at the 2015 15m/Std Class Nationals at Harris Hill

On Thursday, August 13, 2015 at 11:19:09 PM UTC-4, John Cochrane wrote:
Let's remember where the start gate came from.

Faced with the technology of the time, our forebears wanted to figure out how to do an aerial start of the race, so that tow realease time was not start time, and we could tow everybody up in an orderly way and then start the race.

They hit on a great solution: the IP call, and passage of a start line, altitude and passage measured by Charlie Spratt. Altitude had to be low, even heading out over boonies, as one could not reliably measure 6000' starts. Also, there being no way to monitor prestart altitude or speed, a brillaint game developed of getting just the right altitude and blasting through the gate at VNE.

It was a great solution for the technology of the time.

But we don't have that technology. We have recording GPS. If you were to start from scratch and invent glider racing with GPS, you would not invent anything of the sort. It's a solution to a problem with different constraints.

Why go back to something developed on the constraints of visual starts and stretched wire altitude measurement? Just for historic preservation, or because we always did it that way?

If we want to reform starts, think about how we would run races if we were inventing them from scratch, and we will be controlling position and altitude with GPS.

Given that we record GPS, it strikes me the most obvious simplification, and the way we might do things starting from scratch, is a "roll out and go" start. Why start the race when you cross some plane in space, especially given that all the turnpoints are just fixes? Why all the tension about getitng one fix above the cylinder, or maxing your glide to the edge? Why not just have a cylinder, and your best fix in the cylinder is a start, just as an area turnpoint your best fix is the turnpoint. Just roll out and go.

Absent that somewhat simpler system, the current start cylinder does a good job, I think, of controlling a start in a way that is simple for pilots and scorers using GPS technology. A straight line often moves the best start point far away from the airport. Start out the top is brilliant. Measuring speed in the cylinder is impractical: the thing on which you are scored must be easily visible in the cockpit, and with unknown wind there is no way to display the speed on which you will be scored. Diving for a line is a barbaric relic of outdated technology.

The same holds for finishes by the way. The finish line is a brilliant solution to the problem, how do you measure the end of the race by hand and stopwatch. It is not what anyone would invent if they are thinking about the problem from scratch given that we measure races with GPS. It is surely not what anyone would invent in an environment in which all approaches to non-towered airports follow the AIM and arrive for downwind at 800 feet. It was a lot of fun, but we're not necessarily here for historic preservation.

John Cochrane BB

The "best fix" sounds good but it means a competitor doesn't really know when they started till after the race is scored. That just doesn't "feel right."

The "best fix" sounds good but it means a competitor doesn't really know when they started till after the race is scored. That just doesn't "feel right."

Well, that's true now! Quite often, you start out the top, dip back in, and start again out the side... Actually, best start isn't really determined until the race is over. The side start might be faster but under min distance.

We also don't know where the best fix is in turn areas, which doesn't seem to cause that much trouble.

But really, in practical terms, you do know what the best fix is. You're killing time milling around in a thermal. You decide to start. At 90 degrees to courseline, hit the start button on the computer, roll out and go. That will be a darn good fix, and in 1% of the time that some other fix does better, it can only help.

Also this is easy for flight computers to figure out. And since on this forum we'll have computers next year that integrate all the flarm data for the last 6 months, reach out to the internet to grab archived traces, integrate with nexrad to show us bird flocks and the gaggles out on course, anticipating that a flight computer could do for the start what it already does for the turn area seems straightforward!

But this is serious topic drift and a better subject for another time

John Cochrane