Author Topic: 190A5 vs 190A8  (Read 65243 times)

Offline PJ_Godzilla

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Re: 190A5 vs 190A8
« Reply #270 on: April 13, 2010, 01:49:47 PM »
The problem is that a Spit 5 can pull almost 6g at 200mph and a FW190 can only pull 4g.  That means the 190 will have a bigger turn radius at the same speed.  Obviously, things will change as the turns slow to sustained radii.

(Image removed from quote.)

Or am I missing something?
Yes, but, if we do a roll and bank, the 190A has something like 160 deg/sec  -and thus would get to a max bank angle in something like half a second. The Spit IX's is 140 deg/sec MAX and falls off at speed, thus coughing up a couple of precious tenths on a small directional change, possibly. Once we get into a sustained turn, though, per your data, at a given speed, the 190 won't pull the g and is thus liable to suffering tactical reversal. I'm still at time to heading change, if we can call it that, over small intervals, as the real strength of the F-dub - and that the machine was outclassed in sustained turns by the Spit VIII's and IX's - as your plot notes, if it can't produce as much force per unit mass (here's where the wingloading rears it's head, since it enables greater force generation per unit mass) it can't turn as quickly... simple as second law... with the only caveat that the power available has to be sufficient to overcome the increase in induced drag at the higher lift numbers.
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Offline thorsim

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Re: 190A5 vs 190A8
« Reply #271 on: April 13, 2010, 01:55:20 PM »
Yes, but, if we do a roll and bank, the 190A has something like 160 deg/sec  -and thus would get to a max bank angle in something like half a second. The Spit IX's is 140 deg/sec MAX and falls off at speed, thus coughing up a couple of precious tenths on a small directional change, possibly. Once we get into a sustained turn, though, per your data, at a given speed, the 190 won't pull the g and is thus liable to suffering tactical reversal. I'm still at time to heading change, if we can call it that, over small intervals, as the real strength of the F-dub - and that the machine was outclassed in sustained turns by the Spit VIII's and IX's - as your plot notes, if it can't produce as much force per unit mass (here's where the wingloading rears it's head, since it enables greater force generation per unit mass) it can't turn as quickly... simple as second law... with the only caveat that the power available has to be sufficient to overcome the increase in induced drag at the higher lift numbers.


this also plays into my desire to know the relationship between wing-loading and power/weight and how exactly they both benefit the turn. 
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Offline PJ_Godzilla

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Re: 190A5 vs 190A8
« Reply #272 on: April 13, 2010, 02:03:37 PM »
this also plays into my desire to know the relationship between wing-loading and power/weight and how exactly they both benefit the turn.  

For how the powerloading figures, see the equation for max bank. If you figure you've got to support your weight and that the component of lift oppsing it vanishes as you approach 90 degrees bank, you start to see that you have to increase your lift radically at extreme bank and that that will, in turn, drive your induced drag up like the square of Cl. The payoff, of course, is that you direct most of your lift vector at the center of a circle, right? So, powerloading to orient... wingloading to force (both to keep you up and to turn you), is how I see it...
« Last Edit: April 13, 2010, 02:09:27 PM by PJ_Godzilla »
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Offline thorsim

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Re: 190A5 vs 190A8
« Reply #273 on: April 13, 2010, 02:20:24 PM »
i was sort of looking for a qualitative real world test to compare to the math, i think the example i put forward was the extra 300 vs the 540 ...
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Offline Stoney

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Re: 190A5 vs 190A8
« Reply #274 on: April 13, 2010, 02:48:09 PM »
If you have wing planform data and weights for the Extras, we might be able to set up a comparison. 

I'll post some more stuff re: wingloading tonight.  There's an interesting lesson to be learned from looking at the Ta-152's stall speed vis a vis wingloading.

6g is always going to be the limit load factor for us, since everyone blacks out in-game at 6g.  Also, just remember that this is for instantaneous turn rate.  I've got some more stuff I'm developing for sustained turn comparisons, and specific power.
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Offline Bronk

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Re: 190A5 vs 190A8
« Reply #275 on: April 13, 2010, 03:52:29 PM »
ummm data please
I was speaking of in game.
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Offline hitech

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Re: 190A5 vs 190A8
« Reply #276 on: April 13, 2010, 04:32:00 PM »
Gaston Wrote:
[quote}  -Yes it precisely the partial throttle modeling that is off, as is the notion that the best sustained turn rate is reached at full power, [/quote]

It is not 100% clear what you are saying, but if you believe best sustained turn rate with any plane I know of is achieved at less then full power, you have much learning to do.

Best turn rate definition is best sustainable rate of turn in level flight I.E. with out going up or going down or speeding up or slowing down and going around the circle in the least time possible. No plane in the game can even come close to it's corner speed in a sustained turn. You would have to be able to sustain a turn at g limit above corner speed for it to be any use of throttling back.

If you were saying something different in your quote never mind.

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Offline thorsim

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Re: 190A5 vs 190A8
« Reply #277 on: April 13, 2010, 05:39:04 PM »
I was speaking of in game.

ok, don't worry about the data then, thanks for the tip.
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Offline Bronk

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Re: 190A5 vs 190A8
« Reply #278 on: April 13, 2010, 05:56:13 PM »
ok, don't worry about the data then, thanks for the tip.
Not sure if this is sarcasm or not but welcome. You should try it. Spiral up to the right add wep to keep going. When you can get no further try rolling right without cutting power.
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Offline Gaston

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Re: 190A5 vs 190A8
« Reply #279 on: April 13, 2010, 05:57:10 PM »
Gaston has yet to show anything that says that the scale of that torque is anything like significant or, indeed, that even if it is, that such would make any diff, the effect being present in all the a/c, subject to local differences in prop design. Indeed he says as much when he contends that the off-max turn of the Spit will still best the 190, like setting versus like setting. Or, am I missing some assertion he might be making regarding the lower pitch inertia of the 190A? If so, I'd say, "plausible" but that's not going to help overcome the disk effect, which is a torque and will need to be counteracted regardless of source - thus demanding more pitch torque from the tail surface - not something easy to come by in a "close-coupled" (read, short moment arms) a/c.  

His contention on the rest, however, is more clear. He's stating that the 190 a is a better turner at mid-speed off-max than the game credits - yet I see no analytical or test evidence for this assertion - though there is some anecdotal evidence presented. He goes on to dismiss what I feel may be the real turn strength of the 190A - instantaneous turn rate. We are already well-supplied with evidence that it's roll rate is stunning.
http://bbs.hitechcreations.com/smf/index.php/topic,261798.0.html
We need more clarity around his point and, most of all, we need a way to test the hypothesis. That's the only way we'll ever finish this thing.

   The scale of the effect is easy to approximate: If the thrust of the propeller is 4000 lbs, and the upper disc half has 2000 lbs, then pulling back on that upper disc half to make it slightly slower is going to require defeating the entire thrust in that disc half to move it back, even by an infinitesimal amount. A suspended weight of 200 lbs lifted by a 100 lbs of force is still going to leave 100 lbs of tension in that rope...

   The mitigating factor here is that closer to the spinner axis the backward movement is less than at the prop tip: I hear blade center of thrust was at 2/3rds the height, but max height is only in the center of the rotation in profile view, so the "scientific" way of doing this would be to calculate how high the ENTIRE 4000 lbs center of thrust is displaced into the upper disc half, as is accepted by PJGodzilla as being what actually happens on stick pull, and that height of the 4000 lbs center of thrust will then give us the leverage applied by the prop at full power against the wing's center of lift.

    But then you have to take into account the leverage-increasing effect of the prop being at a right-angle to the lenght of the nose, creating a right-angle stress-riser that increase somewhat the actual leverage, given the forward direction of the thrust...

   The FW-190A is advantaged, like all radials, by having less upper disc half leverage agains the wing's center of lift due to the shorter nose, and, by extension, less leverage compared to the elevator's tail lenght leverage...

  The Spitfire probably has to downthrottle lower for its wingloading advantage to emerge.

   The fact is for most of these aircrafts the best sustained turn rate is probably found at around 190-200 MPH, or at least the one that has the smallest radius while STILL equalling the best sustained turn rate, and 160-170 MPH for the Me-109G and Spitfires...

   For all these aircrafts except maybe the really heavy ones: P-47, F4U, F6F, speeds between 250 and 350 MPH are the WORST speeds for sustaining turns because their lower overall weight would allow them to perform better in turns below the speeds where the prop disc load is at its highest.

   As far as where the REAL Corner Speed is for these aircraft, it is so high it is practically irrelevant for WWII combat that is not in a dive of some sort, as it ie "near the maximum level speed" as tested here in 1989:

  
http://bbs.hitechcreations.com/smf/index.php/topic,261798.0.html


   And this, by the way, has been confirmed to me as plausible by an actual aircraft designer... So that 1989 test done by actual modern test pilots is correct in stating the P-51's "Corner Speed" is at around 370 MPH at least, that is, this is around the lowest speed at which 6-7Gs (they tested 6Gs) can be reached....


  It is clear why it is so high: At full power, the prop disc load is at its highest at the middle range of speeds, and the effect is so powerful you have to reach into much higher speeds for the elevator's authority to increase (which it doesn't do on all prop fighter types) while the prop disc load is reduced enough to even allow reaching the "structural limit" of 6 or 7 Gs... On the Me-109G-6 the best sustained turn rate speed was found by the Fins to be about 220 MPH, so you have to go all the way down there to find the first real top sustained turn rate, and going much below that to 160 MPH, with lower power, will tighten the radius without reducing the rate, giving a tactical advantage even if the actual turn rate is not increased beyond that of 220 MPH.

   In any case, it is obvious the effect effect of the prop on the REAL-LIFE wingloading is measured in the thousands of pounds (maybe one, maybe three...)if a downthrottled FW-190A can decisively beat a full-power Spitfire V in sustained level turns...

  Gaston

   I'm sure someone here remembers the thread circa 2004-2006 titled "FW-190A Western ace experience", posted here by a relative who was willing to relay questions to the actual pilot... He said he out-turned a tailing P-51D on the deck in TWO 360 degree turns and shot it down, which I  did not believe until I understood the problem of downthrottling versus full power... (The P-51D had strained so hard he almost stalled in front of him...)

  He is the only source I ever heard speak of field-made aileron hinge "spacers" to increase low-speed sustained turn performance by "catching" the stall... And of the importance of the broad wood prop on low-speed turn performance...
« Last Edit: April 13, 2010, 05:59:50 PM by Gaston »

Offline thorsim

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Re: 190A5 vs 190A8
« Reply #280 on: April 13, 2010, 06:04:03 PM »
Not sure if this is sarcasm or not but welcome. You should try it. Spiral up to the right add wep to keep going. When you can get no further try rolling right without cutting power.

no sir i was sincere, i find them pesky in my a8 sometimes ...

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« Last Edit: April 13, 2010, 06:06:43 PM by thorsim »
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Offline Ack-Ack

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Re: 190A5 vs 190A8
« Reply #281 on: April 13, 2010, 06:18:08 PM »
ok, don't worry about the data then, thanks for the tip.

Widewing awhile back posted a rather indepth thread about the low speed handling characteristics of the Bf 109F and goes into detail about the difficulty of rolling the Franz to the right at low speeds.  If you want to take the time, I do recommend searching for it because it is a gold mine of information.

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Offline hitech

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Re: 190A5 vs 190A8
« Reply #282 on: April 13, 2010, 08:14:56 PM »
Gaston you are completely mixing the terms cornering speed and sustained turn rate. 

They are completely different concepts, cornering speed would be almost identical with engine off or full power on any conventional plane.

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Offline thorsim

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Re: 190A5 vs 190A8
« Reply #283 on: April 13, 2010, 10:04:20 PM »
i thin HTC is missing a big opportunity ...
 
  ***a virtual wind tunnel***

for a fee of course ;)
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Offline Ardy123

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Re: 190A5 vs 190A8
« Reply #284 on: April 14, 2010, 03:25:41 AM »
i thin HTC is missing a big opportunity ...
 
  ***a virtual wind tunnel***

for a fee of course ;)

I actually would love to have something like that for my RC planes... describe them in some virtual 3d format and see how the should perform before I build it... that would be cool.
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