Final glide

On Wednesday, September 25, 2019 at 2:31:32 PM UTC-4, wrote:
On Wednesday, September 25, 2019 at 2:14:48 PM UTC-4, Eric Greenwell wrote:
unclhank... wrote on 9/25/2019 5:41 AM:
On Tuesday, September 24, 2019 at 8:14:29 PM UTC-4, wrote:
Truth, and a final glide made at max l/d tells me that the guy already screwed up. The perfect final glide is one that gets you home at the proper altitude and at the max speed. He just screwed up on both counts.

The "perfect" final glide has the pilot crossing the finish at his selected height and at at the same speed as the average for the flight.

You don't really do that, do you? I'll bet you fly the final glide rather slowly
if your final thermal is weak, and rather fast if that thermal is strong, and
don't pay any attention to how fast the flight was before the final thermal.

That depends on the task. The MacCready theory for final glide speed that depends only on the climb rate in the last thermal applies to assigned tasks. AATs (TATs) are different, *if* your decision (last thermal) happens before the last turn, so that you can then choose, e.g., to fly farther into the last turn area but do the whole final glide (from the last thermal to the turn to the finish) slower. In that case, the optimal speed is the MC STF that corresponds to the average climb rate over the whole task. Yeah I know it sounds weird. Reference: the Brigliadoris' book.

I was commenting related to a preceding post that mentioned being very fast at the line. To have enough energy to be very fast one usually will have flown too slowly earlier in the final glide (assumes that one did not encounter surprise of very good air along the way). We used to do that so we had enough energy to pull up to fly a pattern. We pretty much don't do that any more.
UH

On Wednesday, September 25, 2019 at 8:16:19 AM UTC-7, wrote:
On Wednesday, September 25, 2019 at 10:27:12 AM UTC-4, Dan Marotta wrote:
200'/mile works out to 30:1 since we all use nautical miles, don't we?Â*
That may work just fine back east, but out west not so much. It's
disconcerting to see on the CNII that I need 20:1 to get home but I
can't seem to do better than 15:1.Â* Yes, we have strong thermals, but we
also have some very impressive sink!

On 9/25/2019 8:11 AM, Tango Eight wrote:
On Wednesday, September 25, 2019 at 9:55:44 AM UTC-4, wrote:
Uncl, that is absolutely correct and what I was trying to express. The "perfect" flight would be one of relatively constant avg speed with little difference between normal task cruise avg speed and the final glide speed.

We all know however that that does'nt happen. Most of us do the best we can till we think we have our final glide in hand then modify our speed as we head on in depending on whats happening with our altitude.

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.

T8

--
Dan, 5J

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.

wrote on 9/25/2019 11:31 AM:
On Wednesday, September 25, 2019 at 2:14:48 PM UTC-4, Eric Greenwell wrote:
unclhank... wrote on 9/25/2019 5:41 AM:
On Tuesday, September 24, 2019 at 8:14:29 PM UTC-4, wrote:
Truth, and a final glide made at max l/d tells me that the guy already screwed up. The perfect final glide is one that gets you home at the proper altitude and at the max speed. He just screwed up on both counts.

The "perfect" final glide has the pilot crossing the finish at his selected height and at at the same speed as the average for the flight.

You don't really do that, do you? I'll bet you fly the final glide rather slowly
if your final thermal is weak, and rather fast if that thermal is strong, and
don't pay any attention to how fast the flight was before the final thermal.

That depends on the task. The MacCready theory for final glide speed that depends only on the climb rate in the last thermal applies to assigned tasks. AATs (TATs) are different, *if* your decision (last thermal) happens before the last turn, so that you can then choose, e.g., to fly farther into the last turn area but do the whole final glide (from the last thermal to the turn to the finish) slower. In that case, the optimal speed is the MC STF that corresponds to the average climb rate over the whole task. Yeah I know it sounds weird. Reference: the Brigliadoris' book.

That does sound weird, but I stopped flying contests before the turn areas offered
a large range of choices. Does going farther in that situation add more points,
compared to going faster?

--
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

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

"Back in the day" I used a homemade cardboard circular-slide-rule-type final glide calculator. It had distance and altitude scales, an airspeed scale, and curves for different winds. You set the distance and altitude and flew the speed according to the estimated wind. As the checkpoints went by, you adjusted the alt/dist to actuals and rapidly homed in on the approximate actual wind (conceptually similar to a pre-GPS LNAV, I believe). The finish margin was whatever you wanted it to be mentally. This was how REAL pilots flew: i.e., using a Sectional chart and compass.

I still keep it tucked away in my cockpit for sanity checks when my moving map shows me multiple altitude margins, including margin to gliding to the home airport, margin over the edge of the finish cylinder at finish height, margin to the center of the finish cylinder at ground level, etc. And then my CN vario shows its own altitude, which, as T8 helpfully explained, is always different, apparently based on total energy conserved in a pull up.

I can trust cardboard. It only offers one version of the truth, although it, too, can be fooled by sink, as happened twice this year on final glides at the CCSC Std. Nats that should have been straightforward but were anything but.

Chip Bearden
JB

On Wednesday, September 25, 2019 at 3:45:29 PM UTC-4, Eric Greenwell wrote:
moshe... wrote on 9/25/2019 11:31 AM:
On Wednesday, September 25, 2019 at 2:14:48 PM UTC-4, Eric Greenwell wrote:
unclhank... wrote on 9/25/2019 5:41 AM:
On Tuesday, September 24, 2019 at 8:14:29 PM UTC-4, wrote:
Truth, and a final glide made at max l/d tells me that the guy already screwed up. The perfect final glide is one that gets you home at the proper altitude and at the max speed. He just screwed up on both counts.

The "perfect" final glide has the pilot crossing the finish at his selected height and at at the same speed as the average for the flight.

You don't really do that, do you? I'll bet you fly the final glide rather slowly
if your final thermal is weak, and rather fast if that thermal is strong, and
don't pay any attention to how fast the flight was before the final thermal.

That depends on the task. The MacCready theory for final glide speed that depends only on the climb rate in the last thermal applies to assigned tasks. AATs (TATs) are different, *if* your decision (last thermal) happens before the last turn, so that you can then choose, e.g., to fly farther into the last turn area but do the whole final glide (from the last thermal to the turn to the finish) slower. In that case, the optimal speed is the MC STF that corresponds to the average climb rate over the whole task. Yeah I know it sounds weird. Reference: the Brigliadoris' book.

That does sound weird, but I stopped flying contests before the turn areas offered
a large range of choices. Does going farther in that situation add more points,
compared to going faster?

--
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

Assuming you won't finish under-time either way, going farther (up to a point) gives you more points since it increases the overall task speed (total distance divided by total time). The conditions (average climb rate) determine the best XC speed you can get, along with the STF between climbs, and since the distance is flexible you can maintain that speed for the best score.

What is not clear to me is how do you then decide when to leave that last thermal? Perhaps when the climb rate falls below that average climb rate? Assuming you have enough altitude to reach into the last turn area by that point.

On Wednesday, September 25, 2019 at 4:42:56 PM UTC-4, wrote:
On Wednesday, September 25, 2019 at 3:45:29 PM UTC-4, Eric Greenwell wrote:
moshe... wrote on 9/25/2019 11:31 AM:
On Wednesday, September 25, 2019 at 2:14:48 PM UTC-4, Eric Greenwell wrote:
unclhank... wrote on 9/25/2019 5:41 AM:
On Tuesday, September 24, 2019 at 8:14:29 PM UTC-4, wrote:
Truth, and a final glide made at max l/d tells me that the guy already screwed up. The perfect final glide is one that gets you home at the proper altitude and at the max speed. He just screwed up on both counts.

The "perfect" final glide has the pilot crossing the finish at his selected height and at at the same speed as the average for the flight.

You don't really do that, do you? I'll bet you fly the final glide rather slowly
if your final thermal is weak, and rather fast if that thermal is strong, and
don't pay any attention to how fast the flight was before the final thermal.

That depends on the task. The MacCready theory for final glide speed that depends only on the climb rate in the last thermal applies to assigned tasks. AATs (TATs) are different, *if* your decision (last thermal) happens before the last turn, so that you can then choose, e.g., to fly farther into the last turn area but do the whole final glide (from the last thermal to the turn to the finish) slower. In that case, the optimal speed is the MC STF that corresponds to the average climb rate over the whole task. Yeah I know it sounds weird. Reference: the Brigliadoris' book.

That does sound weird, but I stopped flying contests before the turn areas offered
a large range of choices. Does going farther in that situation add more points,
compared to going faster?

--
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

Assuming you won't finish under-time either way, going farther (up to a point) gives you more points since it increases the overall task speed (total distance divided by total time). The conditions (average climb rate) determine the best XC speed you can get, along with the STF between climbs, and since the distance is flexible you can maintain that speed for the best score.

What is not clear to me is how do you then decide when to leave that last thermal? Perhaps when the climb rate falls below that average climb rate? Assuming you have enough altitude to reach into the last turn area by that point.

For final glide:Based upon current climb rate, with MC set for that, the computer tells you when you are high enough to get back at the selected finish height. One also should adjust for what the sky looks like ahead, what the climb rate trend has been, how tight a margin can be accepted, and then adjusted by a gut factor.
Easy Peasy
UH

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.

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=...Yoq kBwBcDCSY

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/