Corsair Turning Ability in AH

[Knegel]

Originally posted by dtango







Notice how similar the best sustained turn rates are for 0 degrees of flaps vs. 56 degrees of flaps ~25-27 seconds to complete 360 degrees of a sustained turn.

So here we have it again.  The F2A’s rate of climb without flaps is better than the rate of climb with 56 degrees of flaps.  Yet the best sustained turn rates are virtually the same with flaps at 56 degrees vs. no flaps.


Tango, XO
412th FS Braunco Mustangs

Hi,

i just saw this, you be right here, but in oposide to the F4U in AH, the turn rate decrease at least by 2 sec and with only a bit flaps its even worse and at highspeed the turn rate decrease even more in relation to the no flap condition.

Greetings,

Knegel

[F4UDOA]

Knegal,

Look at the flaps (of any aircraft) and lift provided in 1G or turning flight like this.

Do the flaps provide the aircraft more lift than drag at lower speeds and what is there purpose? In the F4U 50 degrees of flap reduces the 1g level speed stall by almost 20MPH with idle power applied. They reduce runway takeoff distance by 30% while allowing the aircraft to takeoff with 5,000lbs of ordinance.

These are all indications that the lift generated by these flaps far out weights the drag created by a good margin. The faster you go the greater the drag becomes and the less efficient the flaps are but at low speeds these flaps are extremely efficient.

[Knegel]

Hi,

your arguments only indicate that flaps lower the sall speed, noone argue this.

The take off run without flaps get even longer than expected, cause the plane dont reach the max AoA with all three wheels down, therefor it have to be much faster than stall speed and therefor the plane need a longer time to accelerate to the needed speed.

My argumentation is that a plane with full flaps have a more bad thrust line, the "excess lift" isnt as high as expected and specialy the drag is very high. All this points dont got recogniced while the simple lift/thrust calculations.
Another point is that a so powerfull plane, like the F4U-4, but also many other WWII planes, should have problems to make a full power turn with full flaps at all. Simply cause the torque is so extreme, while the alerons at 110mph dont work that good, but the planes in AH are most easy flyable while a full flaps stall turn.
Another point is, that the F2A with flaps, no matter what flaps position, show the best tun rate and radius without flaps at speeds above 113mph and this not only in a sustained turn, also while a turn with altitude lost.
While the AH flaps have a better radius and turn rate even at 300mph as result.
What i absolutly dont understand is that the early F4U-1D have a wider turn radius, but gain gain more by using full flaps, like the F4U-4, while the powerload of this planes is much more bad. So much more powerfull plane should be able to bank much more and so the "excess lift" should be higher(that would be my argument for the better turn wihtout flaps, despite the higher weight).
Anyway, the early F4U´s dont have a much better powerload than the F2A and a much worse than the F4U-4, but the radius gain by using full flaps is rather constant.

Iam still sure there is something badly wrong.

But i wanna thank you all for this discussion, i got a better picure of the whole.


Greetings,

Knegel

[dtango]

Knegel:

Don’t you find it odd that Brooke and I, independently doing calculations have arrived at similar conclusions?  Something to think about .  We aren’t making stuff up.

-------------------------------------
You asked a fundamental question in your response to my calculations.  For the basic F4U model I presented …

Q: Why can the F4U perform a steady climb at 100mph @ 2600 fpm at CLmax while it can’t sustain a level turn at 100 mph?

A: Because the F4U is stall limited to perform a level turn at 100mph even though it still has excess power to perform a climb.

In a level turn total Lift must be greater than Weight.

To perform a level turn at 100mph the F4U must produce enough lift to satisfy this equation:

L = W/cos(bank angle)
L= n*W [eqn says: total lift must be greater than weight by “n” amount]

At 100mph wings level, the F4U is flying at Clmax and already producing the maximum amount of lift achievable for that velocity so that L=W.

At 100 mph if you wanted to perform a level turn (without losing altitude), L>W (or L=nW).  To increase lift you would have to increase aoa which is not possible without stalling because you are already at Clmax.

In other words, the F4U is limited by stall and not by power for a level sustained turn in this part of the performance envelope.

Here is another diagram of our basic F4U model with no flaps to illustrate:



This is another view of the calculations for the other graphs I posted earlier.  The top part of the graph are the Power Available and Power Required curves.  The bottom part is the same turn-rate data we’ve seen already.

There are 3 power curves bolded:
1) Pa- Power available (engine_BHP*prop_eff/velocity)
2) Pr 1G- Power required for 1G level flight (drag@1g * velocity)
3) Pr Clmax- Power required for Clmax flight (drag@clmax * velocity)


100mph
===============
At 100mph we have excess power available, but the turn rate is 0.  Why?  Because we are limited by critical aoa (Clmax) for the turn even though excess power exists for a climb.

>100mph to 160mph
===============
Notice the Pa and Pr_Clmax curves.  Above 100mph excess power exists for the F4U until the Pa and Pr_Clmax curves cross at ~160mph.  This means that excess power exists while turning at Clmax in this envelope.

Because we are now traveling faster than 100mph, at Clmax the F4U now generates more total lift than weight to satisfy:

L = nW

Therefore it can perform a level turn.  The maximum amount of lift and thus the level turn performance it can achieve is bound by this equation:

L = .5 * air_density * wing_area * V^2 * Cl  

Within this envelope (100-160mph) critical aoa and airspeed are the primary limit for level turn performance, not power.  In other words we are limited by the amount of lift we can produce and not power.

>160mph
===============
Above ~160mph, power required to turn at Clmax becomes greater than power available.  (You can still turn at Clmax above 160mph.  You would just lose airspeed or altitude which is no longer considered a sustained turn.)  So above 160mph sustained turn performance is no longer limited by the amount of lift we can produce but the amount of power required to hold the turn.

---------------------------------
BTW, the ROC and turn rate charts are correct based on the aerodynamic coefficients and variables used.  There is a minor error for the Ps curve on the turn rate chart which I will fix later when I get home.  On the turn rate chart the Ps curves are actually (Pa-Pr).  It’s supposed to be (Pa-Pr)/W.  The point of Ps=0 doesn’t change.  The shape of the curves change slightly.

I’ll try and answer some of your other questions later.

Tango, XO
412th FS Braunco Mustangs

[SgtPappy]

Hmm. Wish i understood everything. Then perhaps I could fly better heheh.

[Saxman]

Heh. My head popped a couple pages ago.

All I know is the math both agrees with flight data on the F4U referenced by F4UDOA, (both Vought at the time, and current sources) and shows AH has the turn and flap performance more or less correct, while Knegel keeps arguing the point based on test data for an entirely DIFFERENT aircraft even though he's been shown that if he plugs in the necessary data particular to the F2A (prop diameter, engine power, weight, etc) the math works out to fit THAT as well.

[Knegel]

Hi dtango,

thanks for your clarification, i got what you mean, regarding the turn/climb, but actually a "dirty" turn at 100mph is possible. I dont was aware of this and this turn is rather difficult to maintain, but its possible. Its a very unstable nose up turn. Its possible to get there, from the 100mph climb, by banking the plane.
While making a horizontal turn, its not possible to get into this 100mph turn, without to start a initial climbturn.

But i still think that the turn rate with full flaps should be worse than what we have now.

Imho thats caused by the rather bad CD/CL² relation, which at least the F2A show. Where the 10° flap variation should provide a more effective sustained turn.



I dont think that a plane with less effective CD/CL² relation can produce a much smaler radius, without to lose turn rate. And this is only the CD/CL² relation of the wing, the worse thrustline, the wose "excess llift", the greater thrust problems/the higher needed aleron variation etc at slower speed dont will help to offer a so much better turn radius with very similar turn rate, like we have it in Ah now.
Of course, as long as the calculations dont include the disadvanced thrust line and the relative smaler "excess lift" and the other rather problematic factors while slow flights, all looks more friendly.
Specialy for a plane with so much power the thrustline must be a significant influence to the climb and turn.

Some more thoughts to the excess thrust / turn discrepancy i see:

If the plane with full flaps and max AoA climb with 75mph with only 1700ft/min, while the plane with 100mph and also max AoA (close to) climb with 2700ft/min, this display that the drag(not the CD) is much higher with full flaps, despite the fact that the plane without flaps fly much faster, therefor the CD must be even worse.
But in your turn diagram, where also both planes turn with max AoA, one at 100mph, the other at 160mph, both planes offer the same excess thrust.

How is that possible??

btw, the full F4U-4 have its min turn speed at 110mph and 170mph, so accordingto your diagram, the faster plane should turn faster.
And where do you got that curves from?

And Brooke dont had the same conclusion, he wrote that the turnrate should increase with full flaps. That other sims and also AH some time ago  do/did it in the way i say is also something to think about.

Anyway, i think only real tests can show how it realy was, smal different values in the calculation would show how i think it should be.

Are there more tests similar to the F2A around?? Unfortunately thats the only real good turn test i ever saw, specialy with flaps included.

Hi Saxman,

currently i dont saw any turn test for any F4U, the calculations dont include the changed thrustline, neighter the smaler relative "excess lift" cause the slower speed, while flying with full flaps.

Unfortunately the F2A test dont include a climb test with/without flaps, so we also cant get a good idea how the flaps influence the climb at different speeds, i even dont saw any sources to display the influence of the climb speed to the climb rate. So we even dont know if the F4U-4 without flaps had realy a climb ratio of around 2700ft/min at 100mph.

I still have my doubts regarding the way it is in AH now.

Greetings,

Knegel

[dtango]

Knegel:

(1) Brooke came to similar conclusions.  You missed the post I assume.

Originally posted by Brooke
OK, based on the references Tango found, I have updated my calculations for the F4U-1.  See the Appendix:  F4U-1 in this document:

http://www.electraforge.com/brooke/flightsims/aces_high/stallSpeedMath/turningMath.html

The calculations, with actual and wind-tunnel data, agree very closely with the F4U-1 in Aces High -- including that the F4U turns at a higher turn rate with full flaps.

Yes, the F4U in real life does seem to have magical flaps -- backed up by real data and real aerodynamic calculations.

Aces High once again got it right.

(2) You can't extrapolate excess power in a steady climb to vary the same way in a sustained turn.  I already explained why and then went about demonstrating the principles with an example and from the F2A-3 document.  I don't know why you've ignored this.  You can't extrapolate steady climb performance to turn performance.  Excess power depends on load-factor, airspeed, altitude, and e.  



Excluding altitude these are not the same between a turn and a climb.  This has been the main point that I've been actually trying to make.

(3) The F2A-3 tests show climb performance as well and pointed this out to demonstrate point #2.  I discussed this in my detailed post for point #2.  Go back and re-read it.

(4) All the L/D ratio stuff you bring up is included in assessing point #2.

(5) Thrust Line.  Where do I begin?  
a) It's fixed for the aircraft we deal with.
b) Thrust angle is small for the aircraft we deal with so usually ignored to simplify the calcs.  
c) Induced thrust angle changes due to upwash from the wings and impact on lift is embedded in the Cl figures that come from flight/test data with power on.  I calculated Cl based on the numbers you gave (~100mph 1g stall clean, ~75mph 1g stall full flaps) in order to demonstrate point #2 which assumes induced thrust angle changes factored in.  If I use the the power on Cl figures from the F4U-1A test data then the best sustained turn rate is actually better with full flaps than without.

(6) My turn rate chart comes directly from the calculations to demonstrate #2.  Nothing magical going on here.  I didn't make it up.

(7) The faster plane has a higher G in a turn.  This doesn't mean it turns any faster (turn rate) than the slower plane.

turn-rate = gravity * sqrt ( gload^2 - 1) / V

For instance two planes at different airspeeds and turning at different g's:

mph   g   rate
170   2.90   20.1
110   2.02   20.1

Faster plane, higher G.  Slower plane, lower G.  Turn rate is the same though.

--------------------------------------------------------------------------------
This thread has gone on 9 pages and we are just repeating ourselves.  I hate to follow threads that go on ad nauseum !  I'm nearing the point of being finished  with this thread because I don't think anymore discussion is going to help anybody.

Tango, XO
412th FS Braunco Mustangs

[SgtPappy]

Crud. I have to take physics next year! Huzzah! i'm so totally dead.

[Crispy]

Originally posted by Knegel
Hi,

.

There are comparisons, made by US WWII pilots, nowhere you cant read about a extraordinary turn performence of the F4U, actually it got rated as the most bad turning US fighter.
Greetings,

Knegel

Wow now your going overboard, the hog was considered a very manuverable plane.

Another thing, if the hog was so dang uber in AH you would see gobs of them...but you don't...why? it is hard to master...period.  There is SOOOO much more to flight dynamics than simple turn radius.  This whole thread is missing about 95% of  what it takes to "out manuvering" another plane.  Just simple angles...when you pull hard...the attidude you are at when you pull hard...lagging...geeese the list is endless.  The mentality of the game is generaly people thinking how well they can flip flop a plane around...that is actually a very small part of the picture.

I can also tell you have not flown the hog much in AH...with full flaps it pitches around badly...nose bounce is terrible...you need a very delicate hand with many control inputs....even so... bang...your on your back.

You talk about internet sources well keep looking there are plenty actual comparisons of hog tests against many late war models of both sides and it pretty much did out turn any of them (later war planes)  There are many   ... MANY articles placing it as THEE best fighter plane of ww2.  I am not so sure of that but it was very good.

I fly the hog 99% of the time and have for a decade and every time I get in any spit..La..niki...109 I feel like i got out of a pick up truck & into a sports car.

Think past turn radius, the fight is soooo much more than that.

cris

[mtnman]

Another point worth considering-

Planes that are generally known as "turn-fighters" are known as such because of what they flew against, more than how they really turned.  

Compare the F4U to the Zero.  Which one fits the bill as the turn fighter?  Which as the E fighter?

Compare the Spit to a 109.  Turn fighter?  E fighter?

Seldom would anyone not list the spit and the zero as the turn fighters- at least in a general sense, even though the spit is an awesome E-fighter.

What if the war was fought differently?  What if zeros fought spits?  Or 109's vs 190's.  Now which one would be the turn fighter?  Imagine-  spit pilots being told to never turn with zero's!  Fly the hog against a pony and I'm sure the hog would have been considered as a turn fighter.  Pony pilots would have been warned- "DON'T turn against those agile corsairs!"  It gets even worse if we fight hogs with hogs.  Who's the turn fighter now?

The point is that what a plane was "known" for, may not apply in a game like AH.  Not due to lack of realistic flight modeling, but because we don't fight in a "historic" sense.

If we did fight in a historic sense, we'd have a radically different game.  No more "fair" 1v1's.  ALL gangbanging, or at least an attempt at gangbanging at EVERY opportunity.  Lancaster's in the daylight??  Get real!  Occasionally only- the american bombers were much more common in daylight, BUT- only in large formations.  Groups of only three bombers?  Side balancing? Why enable your opponent to have a fair chance?  Kill him quick and decisively.  Go home to your family instead of letting him go home to his.

It seems Hitech has done a pretty good job of modelling a heck of a lot of different planes, and giving us an arena to play with them in an enjoyable atmosphere.  (Maybe a bit TOO addicting, but I'm not complaining...)

It's actually kind of neat that after 9 pages of math and arguments we still can't argue effectively against Hitech's modeling...

MtnMan

[Ack-Ack]

Originally posted by mtnman


What if the war was fought differently?  What if zeros fought spits?  Or 109's vs 190's.  Now which one would be the turn fighter?  Imagine-  spit pilots being told to never turn with zero's!  

MtnMan

Spitfires did fight Zeros and at first got trounced by the Zeros because they tried to turn with them.  The Spitfire units had to adopt US tactics against the Zero and were instructed like US pilots, not to get into turn fights with the far more nimble Zero.


ack-ack

[mtnman]

That's awesome Ack-Ack! I'd never heard that bit of info...  I was just speculating.

MtnMan

[AKDogg]

Originally posted by Crispy
Wow now your going overboard, the hog was considered a very manuverable plane.

Another thing, if the hog was so dang uber in AH you would see gobs of them...but you don't...why? it is hard to master...period.  There is SOOOO much more to flight dynamics than simple turn radius.  This whole thread is missing about 95% of  what it takes to "out manuvering" another plane.  Just simple angles...when you pull hard...the attidude you are at when you pull hard...lagging...geeese the list is endless.  The mentality of the game is generaly people thinking how well they can flip flop a plane around...that is actually a very small part of the picture.

I can also tell you have not flown the hog much in AH...with full flaps it pitches around badly...nose bounce is terrible...you need a very delicate hand with many control inputs....even so... bang...your on your back.

You talk about internet sources well keep looking there are plenty actual comparisons of hog tests against many late war models of both sides and it pretty much did out turn any of them (later war planes)  There are many   ... MANY articles placing it as THEE best fighter plane of ww2.  I am not so sure of that but it was very good.

I fly the hog 99% of the time and have for a decade and every time I get in any spit..La..niki...109 I feel like i got out of a pick up truck & into a sports car.

Think past turn radius, the fight is soooo much more than that.

cris

I agree here with Chrispy.  There so much more to the hog then just flat turns.  When I fly the hog, I not really turning the plane, I rolling into the turn.  I use more rudder then ailerons to turn it.  The Hog has a great tail slide, looping, and hammer head performance.  Zoom climbs with the best of them.  Got good airbrakes.  The list goes on.  IMO the hog has the most options then any other plane in AH during a fight.  If u get a hog on the deck and he just does a flat turn with a spit.  All the spit has to do is spiral climb slightly in the turn and the hog is dead.  No ?'s asked.  Now if the hog pilot is smart and sees this and can't get a shot on the spit, He better pull flaps back up and start to ease off the turn and then level and get speed up.  Even in a chase by a spit on the deck, the hog can kill him with a very simple manev.  I not gonna say what that manev is as it my secret.  I sure mtnman, chrispy and saxman know what manev i talking about.

[Guppy35]

Originally posted by mtnman
That's awesome Ack-Ack! I'd never heard that bit of info...  I was just speculating.

MtnMan

The Hurricane drivers that went out to Singapore and elsewhere expected no problem with the Zeros.  Boy did they find out in a hurry.

The Spit drivers were definately boom and zoom vs the Zekes.