Corsair Turning Ability in AH

[dedalos]

Originally posted by Furball
I wonder why the F4U has no bad handling qualities at all.  It wasn't known as the Ensign Eliminator because it chewed up flags (yes, granted the view didn't help things).  It just kinda floats around like it is on a magic carpet and goes wherever you want it to without any effort.

And if you drop the gear, it floats and climes even better lol.

There was a pach that cam out a while back, around the time of the new look of the planes I think, that took the already perfect flight models of the F4Us and 109s and made them, well, perfect again.  That was the time of a lot of the 109 turning ability and flap usage complaining.  Never seen a complain since then
In anycase, F4Us and 109s fly a lot more like Spits now

[Patches1]

In an F4U...if I have to drop my gear.....I screwed up!

I'd better have a good shot...or else I'm dead.

[Brooke]

I think the F4U and its flaps probably work correctly, but it might be that other aircraft (the P-38 for example) are not as close.  Here is an analysis:

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

[Knegel]

Hi,

as far as i can see this is for levelflight, not for fully banked flights.

As i wrote many times before, the stall speeds are ok in a level flight, while there is a strange discrepancy as soon as the plane is banked.

I would be happy, if someone could explain why the AH F4U lose more than 50% climb performence cause full extended flaps, while the turn rate remain the same.

Afaik in a suatained turn, the turn rate should also decrease(radius remain almost the same) while flying with full falps, simply cause the high drag of the flaps bind to much thrust energy to keep a high banked flight(what is needed to turn tight). At least thats the reason why the plane lose so much climb performence and i dont see a reason why it shouldnt be the same while turning.

And once again, this isnt a F4U specific problem!!

Greetings,

Knegel

[Brooke]

Originally posted by Knegel
Hi,

as far as i can see this is for levelflight, not for fully banked flights.

The two are very closely related.  I'll post the math of it when I can.

[Krusty]

Full flaps should not increase climb much, because they are increasing drag as well. When climbing you're fighting gravity more than when you are turning level.

How did you test climb rate with flaps? Did you just auto climb with flaps out? That is set to (example) 150mph for clean climb. If you drop flaps, the nose pitches down to make up for the drag. In effect, you are reducing climb rate because the auto-trim is trying to keep the proper speed.

You need to set the speed to a lower value, then engage flaps during climb. The problem is the minimum speed allowed for that command is 100mph.

By how many MPH do the flaps reduce stall speed in clean level flight? You will probably need to reduce the auto climb speed by the same amount. You may find that the climb rate does not drop as much.


I used to play around with climbing on flaps. I would engage auto climb, then let the speed equalize, then toggle auto trim off and angle trim on quickly. Then I would pop a notch of flaps. Climb rate increased, but as the aircraft got higher you would constantly have to increase speed (decrease angle of trim) because the air is getting thinner. Then after a while you would slow down because the flaps caused drag. I did this all back when the Ki84 first came out, so it has changed a little since then. However, there was a short term rise in Rate of Climb using flaps in a climb.

[Knegel]

Hi Krusty,

it dont matter if the plane have to fight gravity more while a climb or not, cause we have the climb and turn without flaps to compare.

It need a while until the plane reach a steady climb position with full flaps.

With autoclimb this is rather impossible, cause the plane tend to swing up and down, untill it stall(the autotrim react to slow). I did adjust the trim to keep a steady climb at 110mph.

As i wrote before, the result was 1900ft/min with WEP (F4U-4 100% fuel).

So the climb is by far not better, its much worse, while the turn is better and thats what i dont understand.

That the climb is so much worse  i would explain with the much higher drag, which eat the thrust, needed to climb, but same i would expect while turning.


Hi Brooke,

i agree, the two are very closely related, thats why iam so suprised about the discrepancy between climb lost and turn gain.

Would be nice, if someone could make some calculations regarding the climbrate and turnrate with full flaps.

Greetings,

Knegel

[dtango]

Originally posted by Knegel
I would be happy, if someone could explain why the AH F4U lose more than 50% climb performence cause full extended flaps, while the turn rate remain the same.

Very simple.  The drag associated with flaps is not linear but varies with Cl.


Source: Badboy (from Perkins & Hague)
http://www.badz.pwp.blueyonder.co.uk/images/Flaps.jpg

When you're in auto-climb in AH Cl is lower because the aircraft is at best-rate-of-climb airspeed and supporting lift for 1-g.  Note points A & B on the chart.  For this flap at a lower Cl you have more drag due to the flap vs. not while at the same Cl.  

However, in a turn Cl is greater and supporting lift greater than 1-g.  Note the points C & D on the chart.  At greater Cl you have equal drag with flaps vs. not.  Also for the same drag you have greater Cl with flaps vs. not in this situation.

Tango, XO
412th FS Braunco Mustangs

[Knegel]

Hi,

i did climb at 110mph and did turn at 110mph, as i wrote above, i didnt use Autoclimb.

The points C + D are at stall spead without flaps and it might be that the F4U-4 at stall speed climb even less than 1900ft/min, but this dont explain the discrepancy between a the turn/climb result without flaps at 180mph and the turn/climb result with full flaps at 110mph.

I cant understand why the climb with 110mph and full flaps is so much worse than the climb at 180mph without flaps, while the turn rate remain the same.

Edit:
With full flaps my climb test AND turn test is made at roundabout point "D" in your graphic.

Without flaps the climb test AND turn test is made at roundabout point "A".

And in AH it looks like the much higher CD at "D" cause more then 50% climb lost, despite the much higher CL, but while turing this dont seems to happen.


Greetings,

Knegel

[hitech]

Knegel: You do realize lift has absolutely nothing to do with climb performance correct?

[dtango]

Knegel:

I'm not sure where you're point of misunderstanding is.  The chart above shows you that at higher Cl's there's a part of the envelope that the drag between having flaps vs. not is the same.  So essentially it's the same power required.  The key is at for the same amount of drag you get a higher Cl with flaps.

Why is this important for better turn performance?  Just look at the turn radius and rate equations:

Radius = 2 * (W/S) / g*rho*Cl

Rate = g*rho*V*Cl / 2*(W/S)

Greater Cl, greater turn performance.

Tango, XO
412th FS Braunco Mustangs

[Knegel]

Originally posted by hitech
Knegel: You do realize lift has absolutely nothing to do with climb performance correct?

So we can erase the wings while turning and of course its a myth that the clipped wing Spitfire, despite its a bit more light, have a much worse climb?

[Knegel]

Originally posted by dtango
Knegel:

I'm not sure where you're point of misunderstanding is.  The chart above shows you that at higher Cl's there's a part of the envelope that the drag between having flaps vs. not is the same.  So essentially it's the same power required.  The key is at for the same amount of drag you get a higher Cl with flaps.

Why is this important for better turn performance?  Just look at the turn radius and rate equations:

Radius = 2 * (W/S) / g*rho*Cl

Rate = g*rho*V*Cl / 2*(W/S)

Greater Cl, greater turn performance.

Tango, XO
412th FS Braunco Mustangs

Hi,




This diagram show the influence of the 109E flaps to the Ca, as you can see the Ca get increased much with full flaps and this should influence the smalest possible radius while a sustained turn.
We have a higher CL, which will decrease the decelerated turn(i wrote this before), but the also much increased Ca work against this while a sustained turn.

Your formula is for a constant turn(with altitude lost or with very much power), but i talk about a sustained turn.

If the plane have enough power to fly with the max CL, the turnradius would decrease, but then it also should have the power to climb with the max CL at same speed(like turning speed, thats good above stall speed) and then the climb also should increase.

To have a MUCH smaler turn radius but a MUCH worse climb ratio is what i cant understand.

Btw, i found a F2A article, where the testers wrote that from a speed above 115mph the smalest turn radius can get archived without flaps.
Also in a hight of 27000ft, while a horizontal (sustaied) turn, the smalest radius get archived without flaps, simply cause the plane did miss power to reach the max CL(the drag due to the flaps was to high).
Unfortunately they dont write about a sustained turn in 13000ft(the other test altitude), but they write that they did need to give up altitude to archive the smalest possible radius while flying with flaps, while they could do a max CL turn without flaps without to give up atlitude.

You can find the test on this page:

http://mitglied.lycos.de/luftwaffe1/index2.html

So the question remain, why do we have a so big performence lost while climbing, but not while turning?


Greetings,

Knegel

[gripen]

Well, the material posted by Knegel actually supports dtango's argument. The problem here is that pointing that out will probably take several pages and hundreds (or thousands) lines of text.

[Brooke]

Originally posted by Knegel
Hi Brooke,

i agree, the two are very closely related, thats why iam so suprised about the discrepancy between climb lost and turn gain.

Would be nice, if someone could make some calculations regarding the climbrate and turnrate with full flaps.

Greetings,

Knegel

In my previous post, I meant that stall speed and turning performance are closely related.  Stall speed (or turning performance) and climb rate are not closely related.

I'll post some math when I can.