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#231
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Very long boring technical discussion of Lift Faries adn Thrust
On 2006-03-01 20:42, Jose wrote:
-snip- When you consider how hard gremlins are, and how soft feathers are, it's a natural that feathers repel gremlins, and lift is sometimes erroniously attributed to feathers. Many researchers have been down this path, and there is a large body of accepted literature in support of the feathers theory. At low speeds, the feather theory and the gremlin theory give pretty much the same answers, but at high enough speeds the relationship breaks down and the feather theory gives erronious answers. This is where gremlin theory shines (it should be noted that lift fairies are just gremlins gone bad). Gremlin theory holds the potential for explaining a lot of aviation that is otherwise unexplainable, but experiments are difficult and fraught with peril. However, I would be happy to conduct the appropriate research. Send grant money to Jose, care of Usenet. Jose I'm with you on the gremlins theory; since the feathers theory can be proven to work or not in at least two disparate ways: 1. Why is is that a feathered prop does not provide more lift than an unfeathered one? If the feather theory was correct, it would make sense to feather all props to increase lift. 2. Manned flight would have been possible long ago, by just applying feathers to the human body; while some think this is difficult to achieve, I've read several successfull reports using tar for this purpose. (It is the removing thereof that is the difficult part.) None of the tarred aviators seemed to fly wery well afterwards, so the feathers have been demonstrated not to work in this case. (I note that the excact mass of feathers may have been too small, according to calculations in this group, so I invite anyone to try this method for themselves, to prove or disprove it.) /Rolf |
#232
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lift, wings, and Bernuolli
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#233
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The Impossibility of Flying Heavy Aircraft Without Training
On Wed, 22 Feb 2006 06:15:59 -0600, Immanuel Goldstein
wrote: The Impossibility of Flying Heavy Aircraft Without Training Nila Sagadevan | February 21 2006 Nila Sagadevan is an aeronautical engineer and a qualified pilot of heavy aircraft. And absolutely no common sense, but being this has to be a troll what would you expect. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com |
#234
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The Impossibility of Flying Heavy Aircraft Without Training
On Fri, 24 Feb 2006 02:35:13 -0600, Immanuel Goldstein
wrote: On 2/22/2006 11:07 AM, Robert M. Gary wrote: A local pilot at our airport who owns a small Cessna 210 went to Boeing 737 school a few years back. He was able to shoot approaches to mins and fly quite nicely without any heavy iron training outside of some books and manuals he picked up. Of course, the work gets harder when the instructor starts to simulate things failing. Airline pilots are grossly over paid 99% of the time and grossly under paid 1% of the time. As long as everything is working its pretty easy. Thank you, Robert. This is exactly the reason I chose these groups for my _original_ post. I have a couple of follow-up questions. The local pilot you mentioned was already _quite_ capable of flying a Cessna 210, before attempting a 737. Would someone with little or no flight experience be able to fly a 737, 747, or 757, and also make steep dives and sharp turns? The *big* mistake here is making some wild assumptions. 1. Assuming the pilot is worried about exceeding some or any of the aircraft's limitations. (afraid of breaking it) 2. Afraid of injury. (He plans on dying.) 3. That all maneuvers are performed according to the book. So, steep dives and sharp turns are indeed easy once you have determined the pilot does not care what happens to the airplane, the passengers, what every they might hit, or himself. Standard Boeing commercial aircraft have locks on the cockpit doors. How difficult would it be break one down? Before 9/11 they often stood open whether they were supposed to be shut or not. What are the chances that 8 trained pilots and co-pilots, with military backgrounds, could be physically overpowered by a few thugs with box-cutters? Quite good when you consider back then the training was to try and keep the hijacker calm and reason with them, particularly if they have a hostage. The rule was, "don't make waves" as we might get sued if any passengers get hurt through your actions. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com |
#235
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The Impossibility of Flying Heavy Aircraft Without Training
On Mon, 27 Feb 2006 21:28:52 -0500, Bryan Martin
wrote: I don't know if it was the first time, but it happened once back in the early '80s in, I think, Arizona. I believe it was a PSA DC-9. A disgruntled ex-employee snuck a gun on board and forced his way into the cockpit and shot the flight crew and then dove the plane into the ground. Of course in that case the hijacker had a real weapon and about the only thing that might have stopped him was someone else with a gun. Then of course there is the case of the FedEx DC-10 where the crew barely managed to prevent a nut case soon to be ex-employee from doing the same. The 9-11 hijackers weren't even armed. No mater what anybody says, a box cutter is not a weapon. The only way you can do any serious damage with one is if your victim stands there and lets you do it. Real weapons in the hands of the crew could have stopped them cold. The passengers could have rushed them and put a stop to it. This last scenario has happened at least twice since 9-11. The "shoe bomber' was subdued by passengers. In another case a drunk passenger tried to force his way onto the flight deck and was stopped by several passengers who damn near beat him to death. He was DOA at the airport. Said his heart failed as I recall. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com in article , at wrote on 2/27/06 12:10 PM: Bryan Martin wrote: ... Now we all know just how stupid this policy was. They should have known it before, 9-11 is not the first time a hijacker has taken over an airliner and deliberately crashed it. When was the first time a hijacker took over an airliner and deliberately crashed it? That particular scenario had been considered plausible since at least eh early 1960's and was one of the design criteria for the outermost containment domes at nuclear power plants. |
#236
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The Impossibility of Flying Heavy Aircraft Without Training
Dan wrote: Richard Lamb wrote: Bryan Martin wrote: Bryan, Ex-nay! Or wander over to alt.politics to feed the loons... I brought up this whole Bernouli mess just to get rid of these guys. It worked quite well. Now don't screw it up again! Richard Isn't a Bernouli what an Arab wears? under his theorum :-) |
#237
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lift, wings, and Bernuolli
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#238
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lift, wings, and Bernuolli
On Wed, 1 Mar 2006 at 22:43:58 in message
.com, " wrote: It discussed the Bernuolli theory of flight- and (if I recall) quite conclusively proved that one of the _fundamental_ assumptions of the Bernuolli theory- that air that travels path over the top of the wing is flowing appreciably faster than air that flows over the bottom- is simply incorrect in a compressible fluid.... There is not really a Bernoulli theory of lift. Bernoulli's theory shows the relationship between the velocity and pressure of fluid flow when energy is not added or removed and the flow is subsonic. It is a very simple theory which is correct for much of the time. It quite accurately, at lower speeds, represents the velocity and pressures between streamlines. The air does flow faster over the top than the bottom and for the lower subsonic region air behaves very closely to being incompressible. Generally pressure changes are transmitted at the velocity of sound. At high subsonic and of course at supersonic speed the effect of compressibility cannot be ignored. Shock waves form, first on places like the top surface of the wing where the air first reaches the velocity of sound. As the speed rises they become bigger and move towards the leading and trailing edges. Above Mach one the air does not detect the approaching aircraft! :-) I have just read a few more messages in this thread and discussing lift in this general way without maths and without using at least simple physics and slowly developing the methods is almost futile. What's it matter about lift as long as the aircraft fly? !!!!! -- David CL Francis |
#239
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lift, wings, and Bernuolli
David CL Francis wrote:
The air does flow faster over the top than the bottom and for the lower subsonic region air behaves very closely to being incompressible. Generally pressure changes are transmitted at the velocity of sound. I hate to be a spoil sport (or dullard?), but... the (stationary) air does WHAT (as the wing passes by)??? )) |
#240
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lift, wings, and Bernuolli
Jose wrote: Most aerodynamic equations dealing with low subsonic speeds treat air as an incompressible fluid because compressibility doesn't have a significant effect until you approach sonic speeds. Isn't compressiblity what causes pressure changes (absent temperature changes)? No. Compressible fluids (commonly called liquids) also experience pressure changes. THis is used advantageously for hydraulic power. The distinction is that a compressible fluid (commonly called gas) undergoes a volume change proportionate to the pressure change, while the volume of an incompressible fluid changes little with pressure. Compressible fluids obey Charles' law, (or is it Boyle's law?): P1 * V2 = P2 * V1 -- FF |
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