Another EXTREMELY low thermal save

On Sunday, May 26, 2019 at 1:16:06 PM UTC-7, wrote:
I’m afraid video may be making pilots take these risks.

https://youtu.be/PlXeHeR5Ma8

I can make several comments- but keeping it positive - awesome coordination and concentration. viewing the yaw string and the horizon - neither varied by more than a degree or two and knowing EXACTLY what was needed to get home.
Yes, I agree that newbies or stupid pilots should not use this as a training video

It be nice to see a wider camera angle ... sometimes these cameras don’t tell the whole story due to the field of view (as compared with human eyes and a moving head)

"As I get lower, I think less bank angle in my turns"
Why do you think that less bank is safer ? You can't slow a glider so it stalls/spin at 45 degrees bank, but certainly can at a less angle.
Maybe you mean protection against gusts ?
Dan

On Tuesday, June 11, 2019 at 3:18:43 AM UTC-4, Gary Wayland wrote:
On Sunday, May 26, 2019, at 4:16:06 PM UTC-4, wrote:
I’m afraid video may be making pilots take these risks.

https://youtu.be/PlXeHeR5Ma8

After looking at the video, and the ground underneath, what is the issue?

What am I thinking as he's turning? Well, what is my landing point on a base to final approach? I already have that point picked out on each turn, and it is continually changing as I move with the thermal.

It's clear; he has many landing options.

Next, how much am I going to try to stay in the air based on the bank I have to achieve? As I get lower, I think less bank angle in my turns, and speed, speed, speed. Do not get too slow! If I can't stay up because of purposely putting in less bank angle, then make my final landing because I won't try to stay in the tighter thermal. But as always, I have a point that I keep in my head that is a base to landing point that makes me think I'm at my local gliderport making an uneventful landing.

Well, this is all fine and good if my EGO doesn't overload my good sense!

Gary

"SQ"

On Tuesday, June 11, 2019 at 8:39:51 PM UTC-6, wrote:
"As I get lower, I think less bank angle in my turns"
Why do you think that less bank is safer ? You can't slow a glider so it stalls/spin at 45 degrees bank, but certainly can at a less angle.
Maybe you mean protection against gusts ?
Dan

The steeper the bank angle, the smaller the vertical lift vector component becomes and the greater the horizontal vector becomes. This means that you need a higher speed to generate the same amount of lift. Thus, a slower speed or the same speed could result in a higher sink rate, which could change the apparent wind angle (angle of attack) over the wing and result in a spin/stall. That's the theory at least.

Derek Piggott wrote that in a steep turn the elevator doesn't have enough authority to stall the glider because of the airflow at said elevator.

Works in many gliders. The Puchaz however can spin out of a 45° turn.

Over decades, I have done things that others thought poor.
Then again, I have seen others do things that even I consider poor.

Don't do stupid things.
Doing stupid things at least once does NOT mean you can do it again.
Pride be damned.....listen to others.....reflect...maybe change choices....be aware you will likely be judged harshly on RAS and other sites if things don't work out.
Think about others, mostly family....then friends, local peeps......insurance companies.....etc......
You have no say then, but others will have to deal with YOUR decision.....think about it......

On Wednesday, June 12, 2019 at 12:53:40 AM UTC-4, John Foster wrote:
On Tuesday, June 11, 2019 at 8:39:51 PM UTC-6, wrote:
"As I get lower, I think less bank angle in my turns"
Why do you think that less bank is safer ? You can't slow a glider so it stalls/spin at 45 degrees bank, but certainly can at a less angle.
Maybe you mean protection against gusts ?
Dan

The steeper the bank angle, the smaller the vertical lift vector component becomes and the greater the horizontal vector becomes. This means that you need a higher speed to generate the same amount of lift. Thus, a slower speed or the same speed could result in a higher sink rate, which could change the apparent wind angle (angle of attack) over the wing and result in a spin/stall. That's the theory at least.

Hi John,

Bank angle; meaning, I'm not going to pull a 45/60-degree bank at two hundred plus feet trying to make a low save. If the thermal is that strong that I could pull 45 degrees in a normal condition, then I should be able to flatten out the glider and 'float' my way back out of the hole I just got in. The lower I go, the less bank angle I give myself to save from land out. I start thinking that way under 500' Also note, I talk about speed, speed, speed. "Don't get slow" and drive that in your head in this condition! Also, you better be looking at that yaw string! It has to be in this equation to minimize risk. It's about risk/reward. How much you want to get home based on how much you want to take a higher risk. My chances of falling out are greater with less bank angle but my risks have been reduced based on slow speed (pilot induced), stall/spin high bank angles... I've had some low saves at 250 feet, so this has worked for me.

Question; When do you know you probably should land and not try a save?

Answer; When you have your hand on the gear and jamming it in and out as you find that bit a lift you think is going to save you!



Note; Note the small amount of bank the pilot is putting into the turns. And, he had a bird marker which makes it a lot easier... He was always in control with multiple opportunities to land on the ground. I say, great job!



Regards,

Gary

On Thu, 13 Jun 2019 02:41:26 -0700, Gary Wayland wrote:

Answer; When you have your hand on the gear and jamming it in and out as
you find that bit a lift you think is going to save you!

Disagree. You should be concentrating on flying accurately and paying
attention to what your gluteus maximus and the vario are telling you
about the air, not playing with the u/c lever. That only moves once when
you decide "I'm not finding anything and I'm being blown away from that
landable field, so I AM going to land. Gear down NOW."


--
Martin | martin at
Gregorie | gregorie dot org

At 11:12 13 June 2019, Martin Gregorie wrote:
On Thu, 13 Jun 2019 02:41:26 -0700, Gary Wayland wrote:

Answer; When you have your hand on the gear and jamming it in and
out as
you find that bit a lift you think is going to save you!

Disagree. You should be concentrating on flying accurately and paying
attention to what your gluteus maximus and the vario are telling you
about the air, not playing with the u/c lever. That only moves once when
you decide "I'm not finding anything and I'm being blown away from that
landable field, so I AM going to land. Gear down NOW."


--
Martin | martin at
Gregorie | gregorie dot org

Well said, Martin!
J.

James | MetcalfeIJ at
Metcalfe | gmail dot com

On Thursday, June 13, 2019 at 2:41:28 AM UTC-7, Gary Wayland wrote:
Bank angle; meaning, I'm not going to pull a 45/60-degree bank at two hundred plus feet trying to make a low save. If the thermal is that strong that I could pull 45 degrees in a normal condition, then I should be able to flatten out the glider and 'float' my way back out of the hole I just got in.. The lower I go, the less bank angle I give myself to save from land out. I start thinking that way under 500'

That turns out to be completely wrong. Often, thermals down low are very narrow and you need to really core them with minimum radius. Faster and steeper gives smaller radius, better control, harder to stall, less likely to depart if you do stall, and faster and easier recovery.

All of that applies even more so if you want to add some safety speed "for Mom".

Here are numbers for a glider with 40 knot stall, doing the tightest turn theoretically possible (on the edge of stall):

Speed kts Radius m Bank
========= ======== ====
41.0 141.1 17.9
42.0 102.7 24.9
43.0 86.3 30.1
44.0 76.8 34.3
45.0 70.6 37.8
46.0 66.1 40.9
47.0 62.7 43.6
48.0 60.1 46.0
49.0 58.0 48.2
50.0 56.3 50.2
51.0 54.9 52.0
52.0 53.7 53.7
53.0 52.6 55.3
54.0 51.7 56.7
55.0 51.0 58.1
56.0 50.3 59.3
57.0 49.7 60.5

But that's not very safe. Let's add 5 knots for Mom, keeping the bank angle and G appropriate to the speed 5 knots slower:

Speed kts Radius m Bank
========= ======== ====
46.0 177.6 17.9
47.0 128.7 24.9
48.0 107.6 30.1
49.0 95.3 34.3
50.0 87.1 37.8
51.0 81.3 40.9
52.0 76.8 43.6
53.0 73.3 46.0
54.0 70.5 48.2
55.0 68.1 50.2
56.0 66.2 52.0
57.0 64.5 53.7
58.0 63.0 55.3
59.0 61.8 56.7
60.0 60.7 58.1
61.0 59.7 59.3
62.0 58.8 60.5

Compared to pulling unsafely hard you're adding 36.5m turn radius with 18 degrees of bank, 21.3m with 30 degrees, and only 8.9m at 60 degrees of bank.

But more than that, using 60 degrees of bank is giving a 2 to 3 times smaller turn radius than using 18 to 30 degrees -- and with a better safety margin too.

Yes, you're going to have a higher sink rate. But if it puts you in the core instead of circling outside it then it's well worth it.