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On Apr 25, 8:31*pm, Stefan wrote:
WingFlaps schrieb: Try reading the statement again, here it is: "Now we add in the energy losses from having to accelerate with the wind and to glide speed." To summarise your missed point, the pilot control inputs cost energy that is not factored into simple glide/time analysis. This is absolutely correct. But then, I dont understand the connection to your first statement regarding the wind. Additioinal drag by control input is completely unrelated to the presence or non-presence of wind. Itls a turn upwind to downwind. That involves 2 direction changes, one to reverse course and the the other to line up the runway. If there's wind there will be an effect on line up. Try thinking about more factors that cost altitude OK? Cheers |
#2
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WingFlaps schrieb:
Itls a turn upwind to downwind. That involves 2 direction changes, one to reverse course and the the other to line up the runway. If there's wind there will be an effect on line up. Try thinking about more factors that cost altitude OK? All good and fine, and I'm thinking about a lot of factors, btw. also about human ones which are usually the weak link, but you still have not explained what you meant when you wrote: "Now we add in the energy losses from having to accelerate with the wind." |
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On Apr 25, 10:45*pm, Stefan wrote:
WingFlaps schrieb: Itls a turn upwind to downwind. That involves 2 direction changes, one to reverse course and the the other to line up the runway. If there's wind there will be an effect on line up. Try thinking about more factors that cost altitude OK? All good and fine, and I'm thinking about a lot of factors, btw. also about human ones which are usually the weak link, but you still have not explained what you meant when you wrote: "Now we add in the energy losses from having to accelerate with the wind." Yes, I did. I'll explain it one last time. A direction change in a plane is always due to acceleration (and that means more drag). That's Newtonian physics. You go from up wind direction (takeoff is usually up wind) to turn in the wind direction to land down wind. There's an acceleration, it is a change in _velocity_ it creates drag, it costs height and that's the important bit. Now do you understand -TURNS are not free, they cost more height than the distance covered. Get it now? Cheers |
#4
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On 2008-04-25, WingFlaps wrote:
On Apr 25, 10:45*pm, Stefan wrote: WingFlaps schrieb: explained what you meant when you wrote: "Now we add in the energy losses from having to accelerate with the wind." Yes, I did. I'll explain it one last time. A direction change in a plane is always due to acceleration (and that means more drag). But that's got nothing to do with "having to accelerate with the wind", that's merely the energy cost of making the turn, which will be the same whether there's no wind on the ground, or if it's blowing 20 knots. You're not having to "accelerate with the wind", you're just making a turn and the energy used up in the turn will be the same whether you're going from upwind to downwind or downwind to upwind. Perhaps your original phrase was just a little mis-phrased, because it does make it look like you've fallen for the "dangerous downwind turn" myth. -- From the sunny Isle of Man. Yes, the Reply-To email address is valid. |
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WingFlaps schrieb:
A direction change in a plane is always due to acceleration (and that means more drag). That's Newtonian physics. Right. You go from up wind direction (takeoff is usually up wind) to turn in the wind direction to land down wind. There's an acceleration, it is a change in _velocity_ Wrong. it creates drag, it costs height and that's the important bit. Now do you understand -TURNS are not free, Right. Your're mixing up two completely different things. Of course, turns are never "free". They cost energy due to higher drag, resulting from higher speed, higher wingload and control deflection. *But*: It absolutely doesn't matter whether you turn from headwind into tailwind or vice versa. Your airspeed does *not* change. (Of course the vector does, but not its magnitude.) Your groundspeed changes, but that's not relevant. Your sentence "Now we add in the energy losses from having to accelerate with the wind" can only be interpreted that you think groundspeed would matter because you somehow had to "acceleerate" to catch up with the wind speed when turning from head to tail wind. Which is utter nonsense, Newtonianly spoken. |
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On Apr 25, 11:23*pm, Stefan wrote:
WingFlaps schrieb: A direction change in a plane is always due to acceleration (and that means more drag). That's Newtonian physics. Right. Now we are at first base! You go from up wind direction (takeoff is usually up wind) to turn in the wind direction to land down wind. There's an acceleration, it is a change in _velocity_ Wrong. I see the problem. You don't know what velocity is. It's a VECTOR. It changes when you turn. If you don't understand this there's not much point talking about anything that involves physics.... Cheers |
#7
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WingFlaps schrieb:
I see the problem. You don't know what velocity is. It's a VECTOR. It changes when you turn. If you don't understand this there's not much point talking about anything that involves physics.... Actually, I know an awful lot about physics. In everyday's language, the word velocity stands for the _magnitude_ of the vector. Now if you want me to realise outside some technical or scientific environment that you use the word velocity in the vector sense, you better say so explicitely. Still easier would be to say "direction". |
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On Apr 26, 12:12*am, Stefan wrote:
WingFlaps schrieb: I see the problem. You don't know what velocity is. It's a VECTOR. It changes when you turn. *If you don't understand this there's not much point talking about anything that involves physics.... Actually, I know an awful lot about physics. So much that you mix up speed and velocity? LOL! In everyday's language, the word velocity stands for the _magnitude_ of the vector. Nope. Not even at high school. The magnitude is "speed". Now if you want me to realise outside some technical or scientific environment that you use the word velocity in the vector sense, you better say so explicitely. Gosh, this isn't a technical forum? Was my post not including "technical" terms like acceleration? Still easier would be to say "direction". What does "flying with the wind" imply to you, a direction or a speed? I'd say the former but I'm only a native English speaker. Cheers |
#9
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On Fri, 25 Apr 2008 05:00:45 -0700 (PDT), WingFlaps wrote:
I see the problem. You don't know what velocity is. It's a VECTOR. It changes when you turn. If you don't understand this there's not much point talking about anything that involves physics.... Talk about thick... you don't even have the slightest clue what velocity really is. *snicker* You've been making a supreme fool of yourself all this time, puffing your chest and calling other people stupid in your usual self aggrandizing way. Read this and weep, bitch. Maybe some day you'll learn to not be such an arrogant jackass. ![]() -- John |
#10
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On Apr 25, 11:23*pm, Stefan wrote:
WingFlaps schrieb: A direction change in a plane is always due to acceleration (and that means more drag). That's Newtonian physics. Right. You go from up wind direction (takeoff is usually up wind) to turn in the wind direction to land down wind. There's an acceleration, it is a change in _velocity_ Wrong. it creates drag, it costs height and that's the important bit. Now do you understand -TURNS are not free, Right. Your're mixing up two completely different things. Of course, turns are never "free". They cost energy due to higher drag, resulting from higher speed, higher wingload and control deflection. I'm not mixed up, You wanted to read something into what I wrote that was not there and try to score some point I think Well you were wrong and you still are. I never said airspeed did I? One last time, as succinctly as I can: to change direction requires more energy as extra drag = k.m.dV/dt. dV/dt is acceleration and that is precisely the term I used. The aircraft does _accelerate_ into the downwind direction. Airspeed may not change but _velocity_ sure as hell does -'cos IT'S A VECTOR. Now, the energy needed for the change in _velocity_ comes from the loss of height during the turn and that's easy to calculate. It is much harder to estimate the extra drag loss as this will depend on pilot skill and aircraft design. I hope you finally understand, cos I'm really starting to find it tiresome trying to explain to you some basic physics which you seem intent on mis- interpreting. I'll give you this last post, any continuance along your previous lines of putting erroneous words into my mouth I will take as your being a troll... Cheers |
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