Final glide

On Wednesday, September 25, 2019 at 4:26:19 PM UTC-7, Craig Funston wrote:
On Wednesday, September 25, 2019 at 2:54:10 PM UTC-7, Jonathan St. Cloud wrote:
On Wednesday, September 25, 2019 at 12:49:22 PM UTC-7, Eric Greenwell wrote:
Jonathan St. Cloud wrote on 9/25/2019 12:27 PM:
On a related question, I wonder how many folks here could calculate and perform a successful/efficient final glide without their handy dandy flight computers?
200' per mile plus 1000', and you get home, even in an HP-18 :-).. Back in the day an LNav was 20% of the cost of my glider and GPS wasn't even a thing yet. I had circles drawn on a map and eyeballs to check position. Worked every time, wasn't so hard.
Most people I know use statute miles. I teach using 5 miles/1000 ft as a good final glide reference for Std or 15M ships. Easy to calculate. Adjust for conditions. Pretty much what Evan described but easier to calculate with GPS distance and altimeter.
UH

I have been having a fun summer teaching a Dou XL owner to fly XC. His GPS nor mine was not working for several months and I know the LX9XXX pretty well but didn't know his CNII so we have been using the method I first learnt, 5 statute miles per 1000 ft. We also worked hard on judging distances and estimating what our glide (altitude we would lose enroute) to any cloud, ridge, airport, all glides must be estimated and told out loud. For longer final glides, rather than use something other than 5 miles per thousand, we would add 5, 10 or 15 miles to our estimated distance as a safety factor. We also visually judged and evaluated each glide by the target moving up or down on canopy so we could quickly ascertain how our glide was going. I so much enjoyed the first part of the summer without the computer than we still are not using, at least in the back seat I am not.

How do you account for wind? That's a real value of the GPS base flight computers,
I think.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

Computers are nice and when flying the 29 I certainly use the LX9XXX. We guesstimate wind and add distance to target for headwind. But we are constantly visually checking glide. These are early xc skills that we all learned before GPS and computers. I thought it was very important to teach. I fly with wiz wheel in cockpit for backup but frankly would visually judge glides over using the wheel. I also want my student to develop the habit of mentally checking his computer. I have on two occasions with marginal glide been given faulting computer data. The other thing we work very hard on is judging glides and glide angles and how we are doing on glide.

Lots of good analytical information from John Cochrane. Definitely worth the read.

https://www.google.com/url?sa=t&rct=...Yo qkBwBcDCSY

Or for a deeper dive, Daniel Saznin, et. al. excellent paper on probability in soaring is available here.
https://engrxiv.org/yqgkc/