Author Topic: Maybe the 190s arent wrong....or how to be really unpopular in 1 step (Read 12877 times)

Simaril · « **Reply #60 on:** January 31, 2006, 07:41:00 AM »

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Originally posted by Crumpp
I think your reading that backwards. The P47 gained in the last 3000 feet.

The Dive was from 10,000 feet to 3000 feet. At 3000 feet the P47 passed the FW-190.

Oops. You're right.

A 7000ft drop in alt would definitely count as an AH dive.

I willpoint out tho that my comments are correct with a 7000ft drop in alt.

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Originally posted by Crumpp

I wouldn't say so. We just mounted the armoured glass in Black 3. HTC's cockpit does not account for refraction. You cannot see the armoured glass frame from the inside from the sighting view.

All the best,

Crumpp

I guess I dont follow you here. I'm asking if the cramped cockpit, whcih cant be experienced in front of a monitor, might be effectively modelled by limiting view variability -- ie hard to get around the canopy frames. Im not understanding where the armored glass comes in to refute the point.

Simaril · « **Reply #61 on:** January 31, 2006, 07:49:17 AM »

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Originally posted by Crumpp
In a dogfight it sure is an advantage. The FW-190 would want to force the low slow fight where the ability to turn and accellerate would make a decisive difference.

Of course these findings do not include a substantial power increase to the FW-190 nor the more efficient propellers.

Now as to this point -- the FW advantage only holds if the p-47 agrees to go low and slow.

Two poinits:

One. Both the p-47 and the FW are best used in energy roles. The Fw isnt going to outturn a zeke, or an MA spit. So, when used as appropriate for wingloading etc, the goal woudl be to keep speed up and use energy techniques. IRL, US pilots were hammered with the mantra -- dont go low and slow! The planes were designed for power and speed, and if they were used that way the P47 should win. Over 275mph and all....

Two WE'RE TALKING ABOUT A FREAKIN P-47 HERE!!

You know, the "milk jug"? The beast that was hated when it first appeared -- until the pilots realized it shined at alt? The plane that only a VERY few MA pilots can use as a consistant killer? Crumpp, this is not the cream of the allied crop, and we're bragging that the Fw outmatches it at certain limited points of the flight envelope? Reality check....

Simaril

justin_g · « **Reply #62 on:** January 31, 2006, 08:01:21 AM »

For bozon:

The value of CL will be different depending on the equation used. You can consider a 2d wing which has infinite span, or a 3d wing which has a finite span. Search "Thin Airfoil Theory" for 2d, "Lifting line theory" for 3d.

gripen · « **Reply #63 on:** January 31, 2006, 08:25:27 AM »

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Originally posted by Crumpp
Read the paper Gripen. Or Read Lednicer's article.

Your implication that I don't understand the difference between a unitless CL and a finite span wing is what is entertaining.

The paper you linked and Lednicer's article has nothing to do with this.

Formula of the Cl (used for turning performance calculations) is simply (from NASA):

Cl = L / (A * .5 * r * V^2)

The area of the wing is used for the calculation so the wing span is finite (3D). But calculated coefficient itself does not incluce wing area because Cl is dimensionless factor and that is what bozon asked. 2D is used mostly for wing profile calculations and that has nothing to do with this thread.

Basicly you are showing as large confusion on Cl as you were showing in earlier thread.

gripen

Krusty · « **Reply #64 on:** January 31, 2006, 08:32:32 AM »

Simaril, the P47 in AH is not modeled accurately then, because with flaps it's got BS float capabilities and doesn't stall at all.

justin_g · « **Reply #65 on:** January 31, 2006, 09:36:41 AM »

gripen, that formula is derived from "thin airfoil theory" and it does assume an infinite span.

The formula derived from "lifting line theory" includes a correction for the AR of the wing(ie: induced drag effect on lift).

CL = CLa * (AR/AR+2) * a

Where:
CL = 3D wing lift coefficient
CLa = 2D airfoil lift coefficient slope
AR = wing aspect ratio
a = angle of attack in radians

Obviously if AR approaches infinity it produces the same result as the other formula.

Simaril · « **Reply #66 on:** January 31, 2006, 10:07:25 AM »

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Originally posted by Krusty
Simaril, the P47 in AH is not modeled accurately then, because with flaps it's got BS float capabilities and doesn't stall at all.

I'm not sure about your experience, but I definitely run into stall with the 47 even with flaps full out. If I get too much AoA, or get too heavy on controls at low speed, it definitely stalls....and I generally cant recover from the oscillating control loss at the low alts involved. If you mean that its too easy to fly, well, I cant testify to what it should feel like IRL at that speed so I cant tell if its realistic or not. FIn AH flaps can hold off a stall but you still have to work to manage the bird. I have won stallfighting badly flown Niks in a D25, but a well flown turner will own a perfectly flown jug in a stall fight. Period.

So if "BS float capabilities" means "I dont like it", I cant argue that...but if you mean that it never stalls and is impossibly stable, I've gotta disagree.

It seems to me that stall THRESHOLD and stall BEHAVIOR are 2 different things, and some posts blur the two together. At least one of these reports describes sudden and sharp stall characteristics for the 190 compared to the 47 -- but the stall speed is a different matter.

bozon · « **Reply #67 on:** January 31, 2006, 10:23:52 AM »

ok, lets look at it this way:
1. power required: the energy loss rate to drag. We'll assume all drag is induced as this is the dominant type:
P = r S Cd V^3
where r - density, S - area, Cd - induced drag co-eff.

2. steady alt: lift needs to balance the weight with a bank angle a:
mg = r S Cl V^2 * cos(a)

3. centripetal force: since we want circular orbit:
m V^2 / R = r S Cl V^2 sin(a)

Assumptions:
We assume the thrust is horizontal (parallel to the velocity), it does not contribute to the lift or the centripetal force DIRECTLY. This depends on the fixed angle between the wings and the engine which we do not know and will just serve to complicate things. The angle off the velocity vector will be close to the AoA meaning less than 15 deg. If we try thrust vectoring more than that, we stall the wings since the angle between the thrust and the wing is constant. All thrust does here is allow us to maintain the speed.

Second assumption is that we neglect the viscous drag. Verying S will vary the viscous drag as well but only by a moderate amount (as it includes other parts of the plane as well).

Having 3 equations we can eliminate 2 factors. We are interested in R so lets eliminate the bank angle 'a' - by squaring eq.2 &3 and adding them up. Then we use eq.1 to eliminate the velocity 'V'.

We get a not-so-easy-to-type-here formula for R that STILL INCLUDE THE WING AREA 'S' in a way that larger S make R smaller monotoniously. R is roughly proportional to 1/S. Also we get that P make R smaller down to a minimum value - since we did not allow thrust vectoring where in practice we'd turn into a helicopter. Read the assumptions part again if you think this is a problem

Bozon

bozon · « **Reply #68 on:** January 31, 2006, 10:39:23 AM »

Just one remark.
Wing area reduce the radius monotoniously here since I neglected viscous drag. If we include it, there will be an optimum wing area given all the other conditions constant.

Bozon

38ruk · « **Reply #69 on:** January 31, 2006, 10:48:15 AM »

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Originally posted by Krusty
Simaril, the P47 in AH is not modeled accurately then, because with flaps it's got BS float capabilities and doesn't stall at all.

How much do you fly the P-47? I fly it alot , and i can assure you it STALLS,and does it often when low and slow. I'd sure like to fly the one that your flying .

KAntti · « **Reply #70 on:** January 31, 2006, 11:57:17 AM »

Hehehe, just out of curiousity I went and tried the p47 at low and slow offline

Not only does it not stall, I could lift the nose up to over 60 degrees (starting speed of about 90 mph or so) and lower the airspeed under 50 mph until the stall indicator stops yelling.
And still the only thing the jug does is slightly lower its nose until the indicator starts yelling again. And for the whole time I've kept the stick in my blls and over 45 degree bank and maintained total control of the plane

I've flown AH since beta but never would I have thought that the stall was left out of the equation when you give full flaps. HAHAHAHA

gripen · « **Reply #71 on:** January 31, 2006, 12:11:07 PM »

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Originally posted by justin_g
gripen, that formula is derived from "thin airfoil theory" and it does assume an infinite span.

Yep, but we are dealing here with known wing areas so there is no need to go 2D. The only case we might need 2D is when the Clmax is determined from the wing profile data.

Generally there is no need to mix 2D to this discussion because Cl can be calculated from known wing areas with above simple formula and turn force, turn rate and turn radius can be calculated using the formulas hitech posted which again are very simple.

gripen

Crumpp · « **Reply #72 on:** January 31, 2006, 01:52:28 PM »

Gripen....

Not one single person in this has ever disputed CL is not limitless. You made a wrong assumption.

Hey Bozon,

We sure we want to make these assumptions. All these forces do come into play and affect the aircraft.

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We assume the thrust is horizontal (parallel to the velocity), it does not contribute to the lift or the centripetal force DIRECTLY.

Thrust does contribute to lift. For example:

Simply fly any plane in level flight and increase the throttle:

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If the angle of attack were not coordinated (decreased) with this increase of thrust the airplane would climb. But decreasing the angle of attack modifies the lift, keeping it equal to the weight, and if properly done, the airplane still remains in level flight.

http://avstop.com/AC/FlightTraingHandbook/Thrust.html

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At least one of these reports describes sudden and sharp stall characteristics for the 190 compared to the 47 -- but the stall speed is a different matter.

The FW-190 has two stalls. One, described above is based on the aeroelasticity of the wing underload and the other is when the wing is not deformed.

Very different stalls and behavior. Aileron adjust directly effects this behavior as well.

However I don't think a single player would want the P47 modeled off of Russian data. Or the Spitfire?

So why is it acceptable for an aircraft whose only major fault is the reports are not it English.

All the best,

Crumpp

1K3 · « **Reply #73 on:** January 31, 2006, 01:57:19 PM »

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However I don't think a single player would want the P47 modeled off of Russian data. Or the Spitfire?

So why is it acceptable for an aircraft whose only major fault is the reports are not it english.

gripen · « **Reply #74 on:** January 31, 2006, 02:11:48 PM »

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Originally posted by Crumpp

Not one single person in this has ever disputed CL is not limitless.

Eh... I can only quess you are trying to say that Cl is dimensionless, if so, you are finally learning.

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Originally posted by Crumpp

As Justin pointed out however, there is a difference in 2D and 3D theory.

Well, that is what I'm saying too but 2D has nothing to with this discussion because we are dealing with known airframes.

BTW last time we discused about 2D and 3D you came up with numbers which you have not yet explained.

gripen