Best Fighter III

[Sgt. Pappy]

Oh i thought I've posted the math. My bad. Must've been in another thread.
Click here: The Math Behind Turning
According to those calculations, the F4U-1 Corsair's turn rates on Aces High II are mathematically matching figures to those in real life. The equations are cited and seem to follow what I've learned in physics. The sources seem reliable but I'm still relatively new to the calculations shown so if it has some errors, I probably wouldn't know.

The Spitfire XIV turns worse than the Corsair in the game as well, and if the math seems to prove that the Corsair's in-game figures are correct then the Spitfire XIV figures are also likely to be correct IMO.

 

[Juha]

Hello
IMHO good Bf 109 and P-51 pilots used some 8deg flaps momentarily if they needed momentarily to tighten their turns. IIRC also Fw190 pilots could select "combat" position to their flaps and good P-38 pilots also used sometimes their flaps in turning fight. JAAF Ki-43 had combat "butterfly" flaps etc but Hurricane and Spitfire had only up or full down (80-90 deg) options for flaps and I really doubt that anyone used full down option in turning fight.

Juha

 

[drgondog]

Hello
IMHO good Bf 109 and P-51 pilots used some 8deg flaps momentarily if they needed momentarily to tighten their turns. IMHO also Fw190 pilots could select "combat" position to their flaps and good P-38 pilots also used sometimes their flaps in turning fight. JAAF Ki-43 had combat "butterfly" flaps etc but Hurricane and Spitfire had only up or full down (80-90 deg) options for flaps and I really doubt that anyone used full down option in turning fight.

Juha

Juha - I have been in discussions between many Mustang pilots (and some 109 pilots) that discussed both success and no success using flaps in a turn with 109s. Of course the huge variable is pilot's skill.

Both my father and Warren Peglar were successful at 20,000 feet+ for multiple scores and 'tied' in 15,000 ft range in which other fighter pilots made the score because the Mustangs could not close or close fast enough.

Regards,

Bill

 

[Juha]

Hello Bill
yes use of flaps wasn't a standard tactic exept maybe by Oscar pilots. And when used it was used only momentarily because of extra drag it created. I recall reading one case from Bud Anderson's memoirs and another case from Lipfert's Meine Kriegstagebuch but I'm not 100% sure on latter, might also be from another LW ace's recollections or even from recollections of one of Finnish aces.

Juha

 

[AL Schlageter]

Juha, didn't one of the late war Japanese fighters have automatic 'maneuvering' flaps. Think it was the George but could be the Frank.

 

[Juha]

Hi Al
yes, according to Francillion's Japanese a/c book, older edition, George had that kind of system based on IIRC mercury filled U-tube. I'm not sure if the newer edition still had that info.

Juha

 

[Crumpp]

Let's try to get more exact in the case of the F4U-1, as in Aces High, it is a surprisingly good turner with full flaps.

The Math Behind Turning

I bet it is a good turner with full flaps in a game.

So much for your realism in games......

Have you flown the F4U-1A or 1D before (or its Goodyear or Brewster cousins)?

No I haven't but I do have friends that own them.

Sorry, but full flaps will not improve any aircraft's turning performance. They are designed to make landing the aircraft safe. Doing that is not compatible with improving the turn performance as we simply are not going to have the power required anymore after our plane experiences the increase in drag from the full flaps.

All the best,

Crumpp

 

[Crumpp]

Here Pappy,

This is from one of my textbooks used in my aircraft performance class at Embry Riddle. While the exact percentage will vary from aircraft to aircraft, typically it is in the 50% - 100% range for the increase in drag with full flaps. This means your thrust required increases 50%-100% in the same condition of flight.




Here is what the NACA concluded when they tested the effect of flap usage in 1943:



Here is what an aircraft's bank angle at a constant altitude looks like:



All aircraft have a best turn velocity where they reach a balance of rate and radius. This is found at L/Dmax in thrust producers and Prmin (CL^3/2 / Cd) for Power producers. The correct effect of making a constant altitude full flap turn would be to decrease radius but increase the rate significantly.

Your Corsair and a Spitfire Mk XIV at the same angle of bank and velocity will make exactly the same turn. That is why we have such things as standard rate turns in flying. If you ever go for your instrument rating, you will understand the importance of this fact.

In 99% of the Corsairs and Spits envelope, there is no difference between them in turning ability.

Turn coordinator - Wikipedia, the free encyclopedia

TURN COORDINATOR (ELECTRIC) from Aircraft Spruce

All the best,

Crumpp

 

[Sgt. Pappy]

Ah okay I'm getting it. Thanks Crumpp, that's some good info. Do you own a book where you got this from? I'd like to see if I could find myelf a copy.

Sorry, regarding your last sentence: You mean that if both planes are flown to their respective edges, they will turn at the same rate?

 

[Crumpp]

Modern Jet Transport Performance by James Lewis (Book) in Engineering

Flight Theory and Aerodynamics : A Practical Guide for Operational Safety (2nd Edition) is available from Bestprices.com Books!

Amazon.com: Aerodynamics for Naval Aviators (FAA Handbooks series): Books: Federal Aviation Administration

Amazon.com: Illustrated Guide to Aerodynamics: Books: Hubert C. Smith

And if you really want to know how airplanes work from a practical in cockpit view, my personal favourite. I read this when I was student pilot and at least twice since.

Amazon.com: Stick and Rudder: An Explanation of the Art of Flying: Books: Wolfgang Langewiesche

You mean that if both planes are flown to their respective edges, they will turn at the same rate?

I am saying that for vast majority of the envelope, these aircraft turn exactly the same. There will be some differences in a very tiny portion near the edge, close to the stall point. However it will not be anything that the other aircraft cannot compensate for and match as long as there is altitude.


All the best,

Crumpp

 

[Crumpp]

Pappy,

You do know you already have the information you need. The math on the webpage you keep posting is correct.

What is not correct is the leaps of logic made on it. This is common from those not formally trained in aerodynamics and do not know how to put it all together.

It is no different than seeing gamers argue that the limits set in their "favorite" aircraft can be exceeded. Those POH limits are set for a valid reason.

Go take a flying lesson and dive the plane past the placard limits or lower the flaps above the white arc and see what happens.

Actually don't, as there is a very good chance it will be your funeral, literally. I don't want your family coming back and trying to sue me.

All the best,

Crumpp

 

[Sgt. Pappy]

Haha, well if i manage to fly when I'm a tad more experienced, I may try it.

Thanks for the book links.

It is definitely true that there are biased people on the BBS, trying to prove their plane over the other guy's... but the smart ones do not do that. They simply prove what's needed to be proven. They don't attempt to prove people wrong for that sake, they prove what they find is technically stated to be true. I can't seem to find any 'leaps of logic' in their posts or on the sites... all put together on research.

Maybe I' don't fully understand it all but I know many MANY of the AHII community members have had formal aerodynamics experience as well as some aerospace engineering experience. I very much doubt that they can be biased.

 

[Soren]

All I can say is that if they claim the F4U-4 turns better than the Spitfire Mk.XIV then they don't have allot of credibility.

 

[Crumpp]

Here is what I mean by "leaps of logic". Configuration changes can be very complicated. The best methodology of estimating performance changes is through measured data, without that data, we are really just ballparking it badly. However we are drawing some conclusion off this one report on your webpage that cannot be made.

First of all the report he uses is this one, a wind tunnel test on a scale model. This will result in some very useful data. Unfortunately most of it will not be useful to anyone else but the engineering design team.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930093637_1993093637.pdf

See they have the data to scale the results to the full sized aircraft. That is really is the most common use of Reynolds number. Reynolds number is a representation of the laminar to turbulent flow.

Rg = Vx / v

V = stream velocity of the wind tunnel
x is the distance downstream , in a wing this is the leading edge generally

v = kinematic viscosity

It is easy to prove the data is not scaled by looking at the dynamic pressures. For example, they used a dynamic pressure of 13psf for the climb conditions of the aircraft. Well a Corsair climbs at 125KEAS and the dynamic pressure at that speed is about 52.96psf in an NACA 1922 atmosphere.

Without scaling the data from the model to the actual aircraft, the results are only useful for the engineers for any specific results. For example you cannot say our airplane will achieve a Cl of whatever based on this chart! The values of our ratio of lift or drag pressure's to dynamic pressure will change when they are scaled.

There are some very applicable general conclusions though that we can make off this data.

We can use the L/D ratio of this graph to get some solid conclusions about the general performance of the airplane.

L/D ratio is fixed by design and corresponds to a specific Angle of Attack as long as there is not a configuration change. That is why we can have the Angle of Attack scale at the bottom of the graph. The specific coefficients will change but the ratio will remain the same for given point on the curve that corresponds to a specific angle of attack.

As a rule of thumb, if we divide L/D ratio at a given angle of attack by weight, we get the thrust required to maintain that L/D ratio!

So lets use the same chart on your website:




We have two different Lift to Drag ratio's represented.

The lower coefficient of lift yields an L/D ratio of ~CL1.4 / Cd .165 = 8.48

If our Corsair weighs 12,100 lbs then our thrust required in this condition of flight is:

12,100 / 8.48 = 1427lbs of thrust

In the second condition, we have a much higher coefficient of lift. Someone not formally trained might conclude this were we will get our best performance.

The higher coefficient of lift yields an L/D ratio of ~ CL 2.25 / Cd .385 = 5.84

If our Corsair weighs 12,100lbs then our thrust required in the condition of flight is:

12,100lbs / 5.84 = 2072lbs of thrust required to maintain this condition of flight. A difference of 645lbs which represents a 45% increase in thrust required or drag at just over a 16 degree Angle of Attack.

So go figure how we are going to get a turn improvement in the same condiiton of flight for a 45% increase in drag. The crux is as our aircraft lowers it's velocity, we are even more aerodynamically limited and our angle of bank must get shallower the slower we go.

If we read the conclusions of this Navy report which I posted earlier and is cited on your webpage, you will find them to be true.



http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930092640_1993092640.pdf

How this became "the corsair turns great at full flaps" is an exercise in why formal education is very important. Just because someone works the formulas does not show an understanding of the underlying principles.

Lesson to you, young man..less games and more studying!



I am going to have some turkey! Happy Thanksgiving all!

All the best,

Crumpp

 

[Sgt. Pappy]

Very good writeup indeed, Crumpp. I'll be reading it, and getting a better understanding of all this math hehe. Too bad I'm too lazyto do work... I'd rather play games 8)
But I'll be sure to keep reading.
Have a good Thanksgiving everyone!

 

[Crumpp]

Let me know if you have any quesitons.

All the best,

Crumpp

 

[Soren]

Any news about the addition of the Bf-109 sustained load factors ?

 

[Crumpp]

I'll be reading it, and getting a better understanding of all this math hehe.

Pappy,

One of the reason's for plotting the polars is to both assist and cut down on the math. You can look at the polar and get a good general conclusion on the performance trends.

For example, our L/D ratio is also termed the "glide ratio". The higher airplanes glide ratio is the more aerodynamically efficient the aircraft as a system. An L/D ratio of 8 really means 8:1 or for every eight feet of forward movement our aircraft is losing one foot of altitude.

We can eyeball the polar to get an idea of aerodynamic efficiency of the aircraft in different configurations:



Of course it must be kept in mind too that our structural load limits are greatly reduced the more flaps we add.

Here is what the Corsair's POH restricts the flaps usage for both velocity and manuvering:




Maneuvering under loads at 50 degrees of flaps is not even an option for the pilot. I am sure gamers will be glad to tell you otherwise and how a pilots manual is only a guideline.

Soren,

I will finish work on the analysis on the Bf-109 for you today.

All the best,

Crumpp

 

[Soren]

Excellent Crumpp, thank you

 

[Sgt. Pappy]

I am most often told that the pilot's guide is a guideline, but the wisest gamers in the AHII BBS like Widewing allow students like myself to come up with our own opinions and conclusions by giving us info. Thanks for the charts Crumpp. I've been wondering for the longest time about Glide Ratios.

Yes, I recently just read that '20 degree' part in the F4U manual I had lying around somewhere here.

However, I'm assuming that the full 50 degrees of flaps somehow help aid in lift-off at least on carriers? I remember seeing clean F4U-1's (or 1A's) of the FAA lift off with full deflection. Though I could be wrong; it amy have been 30-40 degrees.