Monday, July 19, 2010

the 100:1 shot

Yesterday turned out to be a mostly local soaring day. The cu would start to build and I would head off with XC ambitions... and the clouds would fall apart literally right before my eyes. So with nothing better to do, I decided to fly "local XC" and work on minimizing my circling time.

You do this by making use of linear sources of lift -- cloud streets, ridges and wave being the most common around here. Since this is something I've been meaning to work on -- my usual style is to cruise too fast, get too low, then have to spend too much time getting back up again -- I have my cockpit PDA set up to track the percentage of time I spend in circling flight. I looked down and noted it said something in the mid 30s -- typical for me and easy to improve upon. So I began working the cloud streets a little harder and concentrating on efficiency. Sure enough, the number in the box starts to drop.

Here's the flight log.

Late in the day (through the magic of "SeeYou" I can tell you it was 3:49) I noticed it was looking really nice towards the White mountains. Kinda late for this... but what the heck. From Exit 14, I made a Mr. Efficiency Glide all the way to Twin Mountain. SeeYou shows this as 42.3 miles at an average ground speed of 81 mph and an achieved glide ratio of -- get this -- 540:1. Along the way, I climbed the ridge at Moosilauke and worked the ridge/thermal lines along the Franconia ridge. I had 15 - 20 mph wind at my back for good measure.

In racing, we talk of "going fast by going slow", and this is about as good as it ever gets.

Coming back up the ridge into the wind, I worked around the corner at Lafayette and wondered if there might be wave in the notch. I worked smoother than normal ridge/thermal lift up to cloud base and it felt pretty wavy, but there was higher cloud all over and the wave wasn't well organized enough to either make a proper window or allow me to climb. But there seemed to be something there. So I headed towards home via Moosilauke and -- with a bit of trepidation -- decided that I'd try it across the wilderness well South of the Franconia ridge line. That worked okay, though I wouldn't try it in a lower performance glider. I made about 35:1 from Lafayette to Moosilauke, which is pretty good considering the absence of clouds and a substantial headwind component. I think I picked up a little wave back there at times.

SeeYou considers my ridge/wave climb at Lafayette to be "straight flight", so credits me with a 26.9 mile glide at 326:1, pretty good considering that headwind! Thermaling up at Moosilauke, Mr. Efficiency flew to Lake Morey where Mr. Speed says "I got it", and that last glide was only good for 29:1.

The end result was 23% circling for the whole flight and an average achieved glide ratio of 96... and a remarkably enjoyable flight for a day that started with low expectations. Next time, we go for 100:1.


PS: Thanks for towing, Tim!


S2 said...

Good flying. I have often wished that you could adjust the SeeYou criterion for "circling." Sometimes I'd like to know my glide performance ignoring the failed thermals.

Anonymous said...

Thanks for the write-up Evan. I find this kind of post very instructional especially when I have been flying that day and saw the conditions first hand.


Anonymous said...

Rick: Right click on statistics page, select "options". Change "Minimum Circling Time" to taste. The default is 30 sec.

After making your change in time constant, you will need to close the flight and re-open (bug in SY) to make the recalculation effective, but it does work.