North Carolina Soaring Association Speed to Fly Fly faster, turn tighter Heinz McArthur North Carolina Soaring Association July 26, 2008

Agenda Glider polars, best L/D, minimum sink MacCready theory Reichman approach John Cochrane: “Just a Little More Speed” Wil Schuemann: “The Price You Pay for MacCready Speeds” Final glides P1 notes

Polars

MacCready Theory Goal: maximize average cross-country speed using optimal inter-thermal cruising speed

MacCready Theory MacCready speeds based on: Glider performance Sink rate between thermals Expected average strength of next thermal MacCready setting = Expected average strength of next thermal MacCready setting = Minimum acceptable thermal strength

MacCready speeds Then Now

Reichman update Thermals tend to be stronger in the center Weaker at the bottom and the top MacCready setting final climb = speed setting = initial climb

John Cochrane During flight figure out/adjust the right level of confidence “How much higher would I have to be in order to finish a minute sooner?” This is the MacCready value Take any thermal greater than the MacCready value; leave any thermal below the MacCready value. Fly the speed ring setting corresponding to the current MacCready value. MacCready value is the weakest thermal you would take for one circle. It is substantially less than the peak climb in the best thermal of the day. As you get lower, take weaker thermals and fly slower. As you get higher, leave weak thermals, stop only for stronger ones, and fly faster.

John Cochrane

John Cochrane

Wil Schuemann

Wil Schuemann

Wil Schuemann Schuemann’s conclusions Moderate speed with little variation costs very little XC speed Reducing MacCready intensity yields more time to think!!! And look outside Increasing range may improve thermal selection Slower flight makes air easier to assess

Final Glide -- DJ Notes Leave the last thermal When you can fly the MacCready speed and reach the goal Plus a safety margin MacCready setting = Average of the last thermal The one you’re in Wind now a factor Glide angle over the ground Flatter with a tailwind Steeper with a headwind As is wing loading and bugs Set your calculator accurately Which requires practice

Final Glide -- DJ Notes Psychological Pressures Glide angle visually flat in modern glas Excessive sink might be encountered Flying fast, loud, low And the turbulence gets rougher lower And the pilot’s IQ starts to fade Tunnel vision/narrowed focus dangerous Must fly the airplane to a safe landing, not just a good finish

Final Glide -- DJ Notes Soaring accidents on final glide Waiting too long to thermal Relying on Zero MacCready to ‘make it’ Off-landing without preparation, from low altitude Analyze fields near the airport

Final Glide – J7 Notes Start shifting mentally to ‘final glide mode’ as early as possible Watch cloud picture as you go into final TP to decide which way to run home Try a 1 McCready setting to decide when to go on final glide On some days it makes sense to start below glide path if cloud picture indicates you can work your way up to glide path while mostly sinking!

Final Glide – J7 Notes When on glide path, turn up McCready setting until you maintain glide path, fly as fast (slow) as you are directed Connect with lift sources, cloud picture on course, pull up in lift Overly aggressive flying puts you in a field! Set your arrival altitude to 700-800’ above home field elevation, go much later to 500’. Allow for another margin if you are not sure of your final glide/wind calculations Be prepared to see the goal airport at a very shallow angle, it looks as if you won’t make it

Final Glide -- XM Notes Set MacCready 3 Leave last thermal when final glide altitude achieved On glide slope, continue MC speed Under glide slope, slow down Over glide slope, speed up

P1 notes Shifting gears Speed-to-fly vs thermal heights Sam Giltner and the blue hole at Winter Haven Speed-to-fly vs thermal heights Do you pull up in lift, speed up in sink? Do you follow the push-pull indicator? Do you set the MacCready “ring”? When? When do you start final glide? What speed?

Wrap up “Deciding when to stop and when to leave, and achieving the best average climb rate, are the most important determinants of cross-country speed.” -- John Cochrane

References Cross-Country Soaring: Helmut Reichmann Cruising for Speed: Sam Zimmerman presentation, 2007 Perry Cross Country Racing Camp Final Glides: Doug Jacobs presentation, 2007 Perry Cross Country Racing Camp Glider Polars and Speed-To-Fly: Bob Wander Just A Little Faster Please: John Cochrane http://faculty.chicagogsb.edu/john.cochrane/research/Papers/#maccready Preparation for Contest Flying: Herbert Killian, Chicago Glider Club presentation http://groups.yahoo.com/group/NCSoaring/files/Presentations/Preparation_for_Contest_Flying-Killian-c.ppt The Price You Pay For MacCready Speeds: Wil Schuemann http://www.betsybyars.com/guy/soaring_symposia/72price.html Training for Cross-Country: Article by Helmut Reichmann

Glider Polars