Mosq's Sustained Turn List 2012

[Slade]

MOSQ,

Thanks for posting the 1 flap data sir. 

[MOSQ]

Mosq it sounds like you're doing minimum speed turns instead of best sustained speed turns. You can see on the EM diagrams that flying slower than your best sustained turn speed is possible but gives you a slower rate and larger radius. Your best sustained turn is typically at 2.5 - 3 G for AH aircraft.

I'm doing the turns exactly the way Badboy does them in "Badboy's Bootstrap Method v1.01, August 2009." And I use his Bootstrap Calculator to come up with the Radius and Rate. We worked together on a custom version of it so I can keep all my other data on the same spreadsheet: See http://bbs.hitechcreations.com/smf/index.php/topic,233819.0.html .

And to clarify, all planes turn a tighter radius, and MUCH higher Rate, at their Corner Velocity speed, which in AH is always the slowest speed that you can turn a 6G turn, than they can turn in a Sustained Turn with No Flaps. But it's impossible to maintain a 6G turn for more than an instant, which is why it's called instantaneous turn.

And ALL planes turn a tighter radius with Full Flaps than they can turn at 6Gs in an instantaneous turn!

There lots of threads and explanations on EM digrams here and SimHQ, http://www.simhq.com/_air/air_011a.html

And finally, I'm no Aerospace Engineer, I'm just trying to provide helpful information. I've been reading Badboy's articles and helping the AH Training corps with data for several years, but as always YMMV!

[MOSQ]

MOSQ,

Thanks for posting the 1 flap data sir. 

 

[FLS]

Thanks Mosq. I didn't mean to imply you weren't doing it right. I probably should have just asked how do you know you're at Ps=0? It seems like I'm stabilizing at a higher speed but I tend to avoid the buffet so I'm probably just not deep enough into the stall to stabilize at Clmax.

[MOSQ]

Thanks Mosq. I didn't mean to imply you weren't doing it right. I probably should have just asked how do you know you're at Ps=0? It seems like I'm stabilizing at a higher speed but I tend to avoid the buffet so I'm probably just not deep enough into the stall to stabilize at Clmax.

No Problem FLS. Yes, you have to go into stall buffet, or at least in and out of it. I try to get into the buffet and if I visually see the horizon is slowing down I let up a tiny fraction so that I'm still just in or out of buffet and the horizon is spinning by at it's fastest rate. WideWing usually beats me at this testing by a few feet  and I think it's because he has a better feel for the buffet.
That's why I'm always open to anyone sending me a film of the test of their favorite plane, and once I verify their test I will modify the listing with their more accurate data. No Film, it didn't happen!
 

[MOSQ]

If anyone wants to know how we do the testing, or better yet do their own testing, I've uploaded two documents to the Skydrive link, Badboy's Bootstrap 3 pdf explanation of the How and Why, and Bootstrap 8L which is the actual Excel Speadsheet calculator. The calculator not only displays Radius/Rate/Corner Velocity/Stall Speed....it will create one and two circle charts for you.

He's posted both of these here on the AH BBS in the past. 

[RotBaron]

Thanks for the work here.

Mosq, in your sustained turn list what is DPS?

Also, I don't understand how corner velocity varies, can someone direct to more detailed information on CV? If there is more than one CV then I don't understand it.  The Bootstrap xls document shows 6 varying CV's for the K-4.

Finally, what is the number in sustained turn rate representing, feet or seconds...?


TIA,

Rot

[MOSQ]

Thanks for the work here.

Mosq, in your sustained turn list what is DPS?

Also, I don't understand how corner velocity varies, can someone direct to more detailed information on CV? If there is more than one CV then I don't understand it.  The Bootstrap xls document shows 6 varying CV's for the K-4.

Finally, what is the number in sustained turn rate representing, feet or seconds...?


TIA,

Rot

Good questions....

DPS = Degrees Per Second = the rate in degrees of a circle you turn each second.

The different CVs in the bootstrap spreadsheet are for each flap setting. Notice the column Flap Notch.

If you do a search of the BBS you will see lots of discussions on Corner Velocity, and the linked SimHQ article by Badboy has a good explanation:
http://www.simhq.com/_air/air_011a.html

Sustained Turn Rate in the Spreadsheet is the same as DPS on my list, Degrees per Second. On the spreadsheet Turn Rate at Corner (meaning at CV) is also Degrees per Second.  Just different term for the same thing.

Glad to see you are playing with the spreadsheet, now do some testing and film them! 

[nrshida]

How do you go about calculating the radius in feet?

[Badboy]

How do you go about calculating the radius in feet?

Suppose you carry out a flight test and you use a stopwatch to time how long it takes to turn in a circle under some set of conditions. You can fly the test under any conditions you wish, providing you keep the speed and altitude constant. But lets say you fly in a circle at a constant speed of 160mph and it takes 18 seconds. From that you can calculate the radius as follows:

1) calculate the speed of the aircraft in feet per second  160*5280/3600 = 234.667 ft/s

2) calculate the distance you travel around the circle in one turn = 234.667 ft/s * 18 seconds = 4224 ft

3) That's the circumference of your turn circle, now find the diameter by dividing by Pi = 4224/3.14159 = 1344.5 ft

4) Now divide that by two to get the radius 1344.5/2 = 672 ft

Therefore if you turn at 160mph and it takes 18 seconds to complete one 360 degree turn, your radius must have been 672ft

Also because you turned 360 degrees in 18 seconds your turn rate was 360/18 = 20 dps

So your flight test gives you a turn rate of 20 dps with a turn radius of 672 ft.

Hope that helps.

Badboy


PS, or you could just use my Bootstrap Calculator

[nrshida]

That's very useful thank you. I was actually hoping there was some way to calculate rates and radii when speed is not a constant.

[Badboy]

That's very useful thank you. I was actually hoping there was some way to calculate rates and radii when speed is not a constant.

Yes there is, but the best way to see the rate and radius at various speeds is to use an EM diagram such as the one shown below that I produced for a real P-51D:


 
Using diagrams like that you can see the turn radius and turn rate at every point in the envelope and of course overlaying the diagrams for different aircraft provides very useful comparisons.

Hope that helps

Badboy

[Badboy]

That's very useful thank you. I was actually hoping there was some way to calculate rates and radii when speed is not a constant.

Ok, on second thoughts you probably wanted a formula to do the calculation yourself.

You can calculate the radius in a flat turn given the aircraft speed and load factor. To be precise I should say the body axis normal load factor, that is the force pushing the pilot into his seat which is different from the force doing the turning, but this calculation takes that into account by leaving 1g vertically so that the aircraft doesn't lose altitude during the turn.

So, let's do the same calculation as before but this time we need the speed and load factor so we have 160mph and 2.735g.

You still need to convert the speed to ft/s as before so we now get 234.667ft/s

The formula and calculation are as follows:

r = radius
v = speed in ft/s
g = gravity (32.2ft/s^2)
n = load factor

Giving...



which gives you 672ft as before.

The difference is that now you aren't doing a flight test, you are using a speed and a load factor to determine what radius that would give you in a flat turn. That's assuming of course that the speed and g are both possible at the same time, but if so, you are good to go.

Was that closer to what you wanted?

Badboy

[nrshida]

Ok, on second thoughts you probably wanted a formula to do the calculation yourself.

Aha! Yes thank you that's perfect. I see your formula even works if the load factor is negative.

I find the EM diagrams to be of limited use because speed is seldom a constant in ACM and they are too static to be practically helpful. I thought it would be an interesting insight to compare rates and radii of a flat turn and a chandelle or a high Yo-Yo. Obviously the BFM which include the vertical element would have a compound curve compared to the simple curve of the flat turn.

[Badboy]

Aha! Yes thank you that's perfect. I see your formula even works if the load factor is negative.

Glad I could help, but that formula is specifically for a flat turn holding one vertical g to maintain altitude. It can be easily modified for turning in the vertical or any other attitude but then you need to do the more involved calculations required to determine how the speed and g will vary during the maneuver. 

I find the EM diagrams to be of limited use because speed is seldom a constant in ACM and they are too static to be practically helpful.

It sounds as though you might not be seeing the potential of those diagrams. That's not to say they don't have weaknesses, they do, but they are invaluable to anyone who has any prospect of dissimilar air combat, real or simulated.

For example, the diagram below is for the Spit9 and includes Ps curve at 25ft/s intervals.     



If you look at this diagram, you can see that if you pull a 5g turn at 225mph, you will have a turn rate of 27.4 dps with a radius of 691ft and a negative excess power of -75ft/s which means that if you want to hold that turn you will either need to descend at a rate of 75ft/s or decelerate at just under 9mph/s. Those figures are giving you rates of climb or descent and decelerations, some very dynamic change! You can see how quickly you would need to descend to maintain the turn, or how quickly your aircraft will lose speed, and you can compare that with any other aircraft, for any other speed or load factor... that's hardly static.

Indeed, diagrams like that are valuable enough to be required ground school material for fighter pilots in the most enlightened military services around the world.

I thought it would be an interesting insight to compare rates and radii of a flat turn and a chandelle or a high Yo-Yo. Obviously the BFM which include the vertical element would have a compound curve compared to the simple curve of the flat turn.

Yes, in a flat turn it is easier to hold the speed and load factor steady and so the turns are close to circular, in steady climbing or descending turns they form a helix. In vertical turns the speed and load factor varies and the curve is more egg shaped, and if you take all the curves together at once the 3D shape formed is referred to by fighter pilots with various names, I prefer to call it the energy egg and it defines the turning environment. I've attached a drawing from a US Navy document.



Calculating those curves will certainly be interesting for you, and possibly challenging, so good luck with that.

Badboy