What's so special about a 45° bank turn?
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- Опубліковано 19 чер 2024
- An exploration of turn dynamics and discovery on how a 45° bank is often the optimum balance for many soaring activities. These dynamics are important for every glide pilot to understand. Learn how bank angle predicably affects g-load, turn radius, stall and minimum sink airspeeds, differential wing speeds, and the need for cross-control use while turning.
Bank angle spreadsheet covering all of these dynamics including the charts used in this video can be found at thesoaringpage.com. An excel spreadsheet version is also available to allow you to insert density altitude and your own glider's variables.
0:00 Introduction
0:08 Check rider requirement
0:51 G-load effect on sink rate and other parameters
1:58 Bank angle effect on turn radius
2:52 Undesirable aspects of a turn
3:12 Effects due to differential wing speeds in a turn
4:45 how to accurately fly a 45° bank
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/ @billpalmer
The "straws on the canopy" video by James Cooper video
"Thermalling Gliders How to Get the First turn right and maintain an Accurate Turn"
• Thermalling Gliders Ho...
(I am in no way am disparaging his innovative technique to accurately fly a 45° bank.)
This is a VERY good tutorial. For the the record, I've been instructing in gliders for 28 years with the Greater Boston Soaring club.
Thank you!
Thanks Bill, well worth watching for all pilots.
This is quality content. Very glad I stumbled upon your channel and page. Thanks Bill! As a physicist and student pilot I could watch this all day.
Awesome video Bill. Thank you for doing these. My kids are home schooled, guess what their new assignment is? Watch every Bill Palmer video before their next flight lesson. Haha
Thank you,
as somebody planning to take on soaring this spring I enjoyed your informative video on UA-cam this morning.
Don’t wait too long. You want to be able to go out in your own when it really gets good!
@@BillPalmer I'm already signed up
You deserve more people watching your videos, Bill. Simply put and well laid information. Thanks for the upload.
Great stuff!
amazing info !
Great video, thanks!
Great video!!
Very informative!
Thanks, Bill!
Nice, concise explanation. Thank you.
Very interesting content. Thanks for it.
Keep doing this type of content please!!!
Bill, well researched and presented; thank you. One small point, which you may have deliberately skipped, is the keeping the yaw string centred idea. With the nose of the glider well forward of the centre of gravity, I tend to have the yaw string a little on the outside of the turn to compensate for this. But again, thank you. I've asked our newsletter editor to include a link to this.
Thanks, That was a bit beyond the scope of the video which was about bank angles.
But let's entertain your point because it's fun to see just how far off it should be.
For the example glider (SGS-233) which at 45° carves a circle about 1050 feet in circumference at sea level (the effect will be less when higher up with a higher TAS and larger circle circumference), with the difference between the location of the yaw string and an average CG location being about 68 inches, to have a 5 inch yaw string tangent to the arc at that point gives it about a 2° deviation -- or less than a quarter inch (3 yarn widths? - less for shorter strings). That yaw string out there on the pitot tube flutters in the breeze more than that, and for students, the goal is to keep it somewhere near the middle.
How far off do you try to put yours?
I think it's a discussion for advanced thermalling. Maybe at the same time we should consider the radius of turn advantage of going slower than min-sink at 45° while incurring a higher sink rate as a result - will having turn radius a few feet shorter pay off with being closer to the core? I don't know but maybe a future Soaring Magazine Aerodynamics Puzzler will address it.
@@BillPalmer Those Soaring Magazine Aerodynamics Puzzlers are outstanding and really make me think - even as a (retired) aero engineer.
@@lautoka63 I love ‘em. I maintain a loose leaf binder of them for my students to (hopefully) read
I saw a video in which the glider pilot demonstrated that he could maintain control in a stalled turn by keeping the yaw string slightly outside the turn. As soon as he centered the string, the glider spun in the direction of the turn. Goes against everything I learned (i.e. always fly coordinated). But then I read an article on the Wings and Wheels website that discusses an article by Dick Johnson on the SSA website called "Circling the Holighaus way".
An excerpt:
"According to the article, the sailplane is more efficient in a slight slip while thermalling. In a slip, you accelerate the lower wing therefore requiring less opposite aileron. The lower deflected aileron creates more lift and more drag. The more aileron you are using the more drag you are creating. Instead, you can use a little rudder and the slip will utilize the dihedral effect (imagine straight and level and you push the rudder over, it will yaw then roll in that direction) and will help maintain the bank angle from over banking.
"One consideration is where the yaw string is located in relation to the CG of the glider. Because the yaw string can be upwards of 2 meters away from the CG and the airflow around the canopy the yaw string indication can be exaggerated. Many times seeing a 10-degree slip is not unusual. Dick Johnson would see up to 20 degrees in his 16.6m Ventus."
@@igclapp Yes, Slipping turns are actually quite safe. In the slipping turn the lower wing’s aileron is UP, reducing its angle of attack in that portion of the wing and the span-wise flow is inward. Contrast to a skidding turn (dangerous) where the lower-slower wing has the aileron deflected downward INCREASING the angle of attack, and the span-wise flow can be disturbed from the fuselage further degrading flow over the wing.
There is defiantly an argument to be made for thermalling in a slight slip that also has to do with aileron position. You’ll find a discussion of that here: thesoaringpage.com/docs/Holighaus%202004.pdf
3:25 More induced drag due to ^ lift.
It would be if we didn't correct for that with up aileron on the outside wing, but we do; however, the speed difference remains and thus the increased drag should mostly be parasite.
@@BillPalmer Correct, with aileron specification.
Im here for the powered pilot comments trying to tell you how its different because they have an engine
Same aerodynamics, but they don’t usually fly in the slow speed sharp turn corner of performance that gliders do. That’s one reason it’s a whole different category of aircraft. It’s really not about the engine. Even motor gliders are still considered gliders and NOT airplanes!
0:57.....'It's heavier'.....not true.....so I stopped.
Well, it IS heavier. Weight is equal to the mass times the acceleration (g force). An aircraft with a higher G load doesn’t gain mass, of course but it does gain weight. In the same what that items in orbit are “weightless” but their mass is the same.
The word heavy is less precisely defined than both mass and weight, but a simple search reveals: “When we say an object is heavy we mean that a great force is needed to lift it. Therefore, the heavy refers weight.”
@BillPalmer Not so. Weight equals mass times g, and g is about 9.8 m/s^2. When an aeroplane banks, it does not weigh more, but there is an extra load on the wings to provide the centripetal force required to make it follow the curving trajectory of the turn. This misconception might not be your fault, since physics is often poorly taught these days.
@@tallbillbassman Indeed Weight = max x G. Sure, when stationary G is 9.8 m/s^2, but G is not exclusively due to gravity. G force is a measure of acceleration. It can be from any acceleration. The combination of gravitational and acceleration vectors(all described as G’s) can compound like a rocket launch or cancel out like in orbit. When an aircraft is in a coordinated turn the total G load is higher , therefore the weight of the aircraft is higher. The G meter in the aircraft does not stay at 1. At no point in the turn do we bank and THEN apply an increased G, it’s done simultaneously. If you bank without turning you’re just slipping. This video is about TURNING.
I really don’t know why you’re trying to argue this. When the higher G force in a turn is applied, the aircraft effectively weighs more and as a coordinated turn requires a higher angle of attack. This is the important concept to present to pilots. In a 45º coordinated turn, they should feel 1.4 g’s and they should know their performance and stall speeds go up almost 20%. Which creates a reduced margin between their current AOA and the critical AOA. THAT’s the point.
The chicken-egg argument of which vector came first is NOT the point here (though it may be in physics class).
Nothing spoeial about a 45" turn.
Well, let’s see:
Minimum altitude loss per turn
Near optimum bank for thermalling
Maximizing adverse effects of increasing bank and yaw away from the direction of turn.
Not nothing.