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Luftwaffe and Axis Air Forces Please use this forum to discuss the German Luftwaffe and the Air Forces of its Allies. |
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#161
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Re: Performance of the Fw 190A on the Deck?
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And it really is related to the laws of physics. Quote:
I don't claim that my calculation is a precision model, as example Holtzauge has far more sophisticated model; still, we got similar results for this particular problem. However, I do claim that it is good enough for testing the scale of the effect, to test Graham's statement in other words. Small errors in n, e, compressibility effects, Cd0 etc. do not cause large difference. |
#162
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Re: Performance of the Fw 190A on the Deck?
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That is a start. My suggestion would be to go find someone you trust whom is actively teaching or working in the industry. You are obviously an older guy if you have been doing model toys for 25 years. Perhaps taking an adult education class is another possibility. Only observing direct results can get us into trouble in science and engineering. One must understand the cause and affect of the underlying forces not just looking at simple end results. All the best, Crumpp |
#163
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Re: Performance of the Fw 190A on the Deck?
I think the original topic of the thread was indeed "the simple end results" — could an Fw 190 pilot on the deck get away from the guy who was trying to kill him? Live or die? Simple end results.
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#164
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Re: Performance of the Fw 190A on the Deck?
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A Focke Wulf running from a P51 is not really a complex system, Nick. It's a simple foot race which was pretty much answered in the first few posts. Is this still a question in people’s minds? That is a far cry from the science behind the statement fuel affects are insignificant because we only perceive a small drop in velocity. That was nicely demonstrated by Harri Pihl’s own math. See his post #150 http://forum.12oclockhigh.net/showpost.php?p=70836&postcount=150 And my reply in # 151 http://forum.12oclockhigh.net/showpost.php?p=70846&postcount=151 Weight affects are a complex system and we know the affect of weight does not change at high velocity. There is change in the aircraft's ability to compensate for that affect but the affect of weight is exactly the same. All the best, Crumpp |
#165
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Re: Performance of the Fw 190A on the Deck?
My point exactly — but there seem to have been another 16 or 17 pages since then.
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#166
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Re: Performance of the Fw 190A on the Deck?
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All the best, Crumpp Last edited by Crumpp; 10th August 2008 at 19:39. Reason: clarity |
#167
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Re: Performance of the Fw 190A on the Deck?
Well, there are no outran Fw 190 pilots alive for obvious reason.
I am afraid, I am slightly lost as to what is the current problem with thrust. Just too many posts, almost at once. |
#168
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Re: Performance of the Fw 190A on the Deck?
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And without continous personal remarks and harsh language, you have presented. Well, you just calculated how much additional speed was needed to maintain the Cl. And that is impossible at constant power, the top speed situation ie aircraft has no such ability. |
#169
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Re: Performance of the Fw 190A on the Deck?
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Edit: actually the post #21 |
#170
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Re: Performance of the Fw 190A on the Deck?
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I think you have been very rude. Quote:
Harri Pihil, I calculated the affect of weight on the aircraft. That affect does not change simply because the aircraft no longer has the ability to compensate for it. This is not the Mulberry bush for us to go round and round. You claimed: ---------------------------------------------------------------------- Quote: Quote:
The lift coefficient at 9680lbs (4390,85kg) and 352mph (566,37km/h=157,324 m/s) at sea level is, as allready demonstrated: Speed V =157,324m/s density r = 1,225kg/m3 wing area A = 21,83m2 Lift L = 4390,85*9,81 = 43059,51 N Cl = L / (A * 0,5 * r * V^2) = 0,13011 At 10280lbs required lift is: L = 4663,01*9,81 = 45728,487 N So we can solve the required speed at constant Cl at higher weight using these: V = SQRT( L / (A * 0,5 * r * Cl)) = 162,17m/s = 583,66 km/h And we can check this with your formula as well: V2/V1 = SQRT(W2/W1) 583,66km/h/566,37km/h = SQRT(4663,01kg/ 4390,85kg) 1,031 = 1,031 So we can see that both calculations methods give the same result for that specific problem. However, the result for this specific problem, the speed change required for constant Cl at higher weight, is over ten times higher than the result for the problem in our hand. Note that we calculate steady conditions here ie D=T at level flight. Speed change due to weight change if power is constant and the other parameters are adjusted accordingly as demonstrated earlier is: delta V = -1,48 km/h while the speed change to keep Cl constant when the weight change is: delta V = +17,3 km/h We can also calculate the power required using the similar drag and thrust calculations as demonstrated above and we find that this higher speed at constant Cl requires 1748,98hp ie 169hp more than with original values (assuming otherwise the same parameters, including exhaust thrust). What we see here is: 1. Calculating speed change to keep Cl constant at varying weight is completely different problem than calculating speed change at constant power when the weight changes (ie our problem in hand) 2. The magnitude of the results is completely different, over ten times difference in this particular case. ------------------------------------------------------------------ ------------------------------------------------------------------ I responded: ------------------------------------------------------------------- Now we are getting somewhere! Quote:
Certainly! Why is that change so small? What the differences? Because the aircraft does not have the Power available to meet the new power required! The Angle of attack must increase and the velocity slow down. Of course in a propeller aircraft as our velocity decreases we know our thrust increases! The affect of weight is very much present and the aircraft's entire envelope is still reduced There is change in the aircraft's ability to compensate for that affect but the affect of weight is exactly the same. No change in the significance of weight. So this result: Quote:
Is really exactly the same as this result: Quote:
As demonstrated by your first set of calculations: Quote:
So when we isolate the affects of weights in a parametric study to see the true affect, we can only conclude that weight has very significant affects upon an aircraft, even at high speeds. All the best, Crumpp Last edited by Crumpp; 10th August 2008 at 21:49. Reason: added correct quote marks |
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