h a l f b a k e r yI like this idea, only I think it should be run by the government.
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
browse anonymously,
or get an account
and write.
register,
|
|
|
Mythbusters proved that rotation of aircraft wheels -- with the assistance of a conveyor belt -- and possibly the ensuing gyroscopic force of the spinning wheels -- provides the lift, (not the wing) (1) and allows an airplane to take off without the necessity of a runway. Spinning the wheels before landing
would also create lift and allow the airplane to make a vertical landing. Who needs wings or rotors!(2)
2016 05 06 Edit: If I were a politician I would say "I misspoke." Since I'm not I'll say I was wrong, I think. Upon watching a rerun of the show I could find no circumstance were Adam stated the airplane took off sooner on the canvas than it did on the concrete.
Without a tarp, in standard takeoff mode, the airplane took off within 85 feet. Jamie and Adam placed road safety cones beside the canvas. I don't know if this was to mark the takeoff distance of 85 feet are not. When the airplane took off on the canvas it took off right at the end of the road traffic cones. Again I don't know if the traffic cones were marking the original 85 foot takeoff mark. Maybe Adam did say that the airplane took off sooner on the canvas and this was edited out in the rerun… I don't know and would like to know if anyone else heard that comment on the original airing is stated previously on 20151119. Apologies. I hope I don't suffer the wrath of others who have been cited for scientific misconduct :-)
Added 2029 4 10 See link [1]by a person that thinks the conveyor belt allows a faster takeoff and shorter runway than if no conveyor belt was moving under the plane
However, I still remain fascinated with the airfoil argument and would like to see this "myth" tested in the new MythBusters series that is under development.
***
Means to eliminate the conveyor belt:
Plan 1. Simply jack the airplane up slightly, spin up the electric motor in the wheels (3), similar to the electric motors in hybrid cars, and take off vertically
Plan 2. Place a cradle roll chassis dynamometer (rolling road) type device under the aircraft wheels and have the rollers spin the wheels rather than have the wheels spin the roller as on a dynamometer. The airplane will takeoff vertically.
Better yet, forget the airplane altogether, Spin the wheels on your bike, motorcycle, car, boat trailer, or whatever and fly away. Greyhound Bus Lines could now compete more directly with Airbus and Boeing. We just may have created an anti-gravity device industry here. So long to airports.
(1) Lift is not caused by airfoils anyway. Otherwise, ring wing airplanes, paper airplanes, cheap balsa gliders, flat "profile" wing control line and radio control planes, airplanes flying upside down or on their side (knife edge flight) would never fly. Fully symmetrical airfoils would cancel out their own upward and downward lift. An airplane can't takeoff or climb without "rotating" to get the leading edge up to catch air and fly. Airplanes must have an angle of attack in the wing to catch air, otherwise a tricycle gear airplane would not leave the ground. Airfoils are simply aesthetic covers for wing spars. The Wright Brothers and earlier designers copied the "bumps" on the top of bird wings -- which simply smoothly covered the "spar made of bone" in the bird's wing. All other aviation designers later copied the same design as monkey see monkey do. When a material strong enough is created to allow flat wings without spars on full size planes, the aesthetic spar covering hump will no longer be needed.
(2) Aircraft equipped with skis and floats would have to incorporate spinning wheels into their designs as well.
(3) These are the same motors proposed in patents that start the wheels spinning before landing so you don't get that "eeek," Eeeek" sound as the non turning rubber hits the runway and is unnecessarily burned off while scaring the passengers.
Could be I'm just joking about all this. Maybe, maybe not.
I'm not finished yet: It is well known that to get maximum thrust from airplane and boat propellers, and helicopter rotor blades, one goes to a flat pitch so the airfoil is 100% exposed and all angle of attack or pitch is removed. Any increase in angle of attack or pitch angle causes the prop or rotor to stall and lose thrust. Autogyros, likewise, will not fly if the rotor pitch is anything but flat. No?
2016-02-28 Note that the horizontal stabilizer on an airplane is also an airfoil. This lift producing stab creates a constant, highly leveraged (due to the length of the fuselage) rise of the tail-plane that forces the plane's nose downward. This stab lift induced dive forces the pilot to trim the elevator heavily into a climb adding much drag which results in reduced flight speed. Horizontal stabs should be flat rather than airfoil-less to stop this problem that has impeded advancement in aviation in the same way that compressibility hindered early sound barrier breaking flight attempts.
By the way, Edward Snowden hacked :-) NASA's research on airfoil theory conflicts and discovered exactly why wings aren't needed. See link (A)
"In fact, since the conveyor belt would drag along a bit of air due to simple friction the plane would actually get into the air _quicker_ than if it was taking off from a normal runway. The conveyor moving in the opposite direction would drag a bit of air backwards with it, increasing the relative airspeed of the wing and increasing its lift (there may be some additional ground effect in play here that assists the takeoff as well…)" [1]
Another way to get rid of runways would be to have devil possessed levitating persons pilot the planes. [2]
Added 2020 4 12 Excellent annotation by "wit:" "a plane could be spun up via a wire cable anchor point in one of the wings" This can and does work. Search for "discus launch glider" and see videos of model glider flyers holding a wingtip spinning round and round releasing their planes to get airspeed and lift. This would be a hell of a G-force on pilots and passengers though. But doable for for very light planes like drones with strong wing spars designed for the job -- recognizing the "Let's put some numbers on that" comment of 8th of 7. Love it!
Added 10 23 2020 In these trying times of need I must add another rotation related device that gets the plane off the ground in a jify ...the Magnus effect.
See the "Spinny Bird - Weird Magnus Effect R/C Aircraft" video on the net. One day you will realize why UFOS are shaped to spin and why wound alarm clocks weigh more that unwound alarm clocks.
Mythbusters proves wings are not needed (conveyor belt makes plane lift off quicker but can't find a full video of the segment)
https://www.google....al&client=firefox-a
I wish I could link to the full airplane on a conveyor belt Mythbusters segment rather than just the last part. As I recall the plane was off the ground quicker when on the belt versus off the belt. If anyone recalls this please comment. More fun discussion of the topic at http://web.archive.org/web/20090104025255/http://community.discovery.com/eve/forums/a/tpc/f/9401967776/m/4441931059?r=5311922059 and https://duckduckgo.com/?q=conveyor+belt+airplane+takeoff&t=ffsb [Sunstone, Feb 17 2013, last modified Jan 02 2016]
Airfoil Lifting Force Misconception Widespread in Textbooks
http://amasci.com/wing/airfoil.html
[Sunstone, Feb 17 2013]
RIng style airfoil
https://www.google....gUcXwMoe08AS06oHYBg
[Sunstone, Feb 17 2013]
In wheel motors
https://www.google....b7&biw=1024&bih=548
[Sunstone, Feb 17 2013]
Cradle roll chasiss dynamometer
http://www.land-and...no/chassis-dyno.htm
[Sunstone, Feb 17 2013]
D-Dalus rotatry lift-system
http://www.gizmag.c...s-uav-design/18972/
Not your grandfather's airfoil. [Vernon, Feb 17 2013]
How airplanes fly
http://en.wikipedia.org/wiki/Aerodynamics
It took me a long time, but I finally found a resource that explains the elusive secret of how airplanes _really_ fly. You may be surprised at the truth! [Alterother, Feb 17 2013, last modified Feb 18 2013]
No tire spin needed
https://www.youtube...watch?v=f7u1jzjFL8s
10 foot landing and 10 foot take-off. Doubt his wheels were spinning very fast. [Klaatu, Feb 17 2013]
Confused aeronautical engineers increase wing angle of attack on carrier launched XFTU-1 fighter to improve takeoffs/climb rate
http://www.fiddlers...Vought-Cutlass.html
"The XFTU-1 had an elongated nose strut to elevate the ground angle to increase the wing's angle of attack for catapult launching. On the prototypes, this angle was 9 degrees. To further improve the launch characteristics, this angle was increased to 20 degrees on the F7U-3." Now why would they increase angle of attack, all the lift is created by the airfoil!? [Sunstone, Oct 17 2013]
FJ-2 Fury has variable angle of attack for carrier launch
http://www.gosurnew...ing-film-wdtvlive42
What;s with these designers; were they not taught that airfoils create all the needed lift?! [Sunstone, Oct 17 2013]
On the Vought F-8 Crusadrer they called it a "variable-incidence wing'
http://en.wikipedia...Vought_F-8_Crusader
The definition of aeronauticle engineering insanity is to keep doing the same thing over and over? [Sunstone, Oct 17 2013]
Variable-incidence wing history
http://en.wikipedia...able-incidence_wing
[Sunstone, Oct 17 2013]
Angle of attack is the secret of flight
http://www.amazon.c...lying/dp/0070362408
The invisible secret of all heavier-than-air flight: [downwash] from the Angle of Attack - What it is, and why it can't be seen. STICK AND RUDDER remains the leading think-book on the art of flying. STICK AND RUDDER is the first exact analysis of the art of flying ever attempted. It has been continously in print for thirty-three years, and has enjoyed steadily increasing sales. When STICK AND RUDDER first came out, some of its contents were considered highly controversial. In recent years its formulations have become widely accepted. Pilots and flight instructors have found that the book works. [Sunstone, Dec 02 2014, last modified Oct 30 2017]
What keeps planes in the air is the downward force created by the wing; the aircraft mostly pushes itself into the sky
http://www.straight...irplanes-fly-really
As with many other scientific phenomena, it's not always necessary to understand why something works to make use of it [Sunstone, Dec 02 2014]
Forget Bernoulli's theorem
http://www.aopa.org...he-angles-the-thing
"A wing is an odd thing, strangely behaved, hard to understand, tricky to handle. In many important respects, a wing's behavior is exactly contrary to common sense." [Sunstone, Dec 02 2014]
Magnus Force
http://en.wikipedia.org/wiki/Magnus_force
I still don't get why the author thinks this will help, but clearly is talking about magnus forces on spinning objects. You will note that magnus forces are a product of a spinning cylinder moving through a fluid. With no movement, there is no force. [Custardguts, Dec 03 2014]
B the flying car
https://www.kicksta...7062404/b-go-beyond
Lifting wheels, sort of. [BunsenHoneydew, Dec 05 2014]
Giant flying paper airplanes sans airfoils and spars
https://duckduckgo....fsb&iax=1&ia=videos
[Sunstone, Nov 19 2015]
(A) Watch this gyroscopic precession wheel fly. Yeah baby!
https://www.youtube...watch?v=GeyDf4ooPdo
Anti gravity wheel [Sunstone, Nov 19 2015, last modified Feb 29 2016]
Paper airplane flat wing argument
https://aviation.st...heir-wings-are-flat
[Sunstone, May 03 2017]
The wingless aerodyne
http://www.rexresea...ppisch/lippisch.htm
Drones ain't nothin' new. Just ask Mr. Lippisch about his blimp looking drone with fans in it. He was just a hair off a quadra-copter [Sunstone, May 03 2017]
Wikipedia: Magnus effect
https://en.wikipedi.../wiki/Magnus_effect
Mentioned in my anno [notexactly, Sep 19 2019]
[1] Faster takeoffs on a convyer best. Great for aircraft carriers
https://kottke.org/...plane-conveyor-belt
the plane would actually get into the air _quicker_ than if it was taking off from a normal runway. [Sunstone, Apr 10 2020]
[2] Demonic possession and levitation
https://duckduckgo....on&t=ffsb&ia=videos
[Sunstone, Apr 10 2020]
[link]
|
| |
I think you should revisit that episode of Mythbusters, you seem to have taken the wrong message from it. |
|
| |
Congratulations. This is written just clearly enough to make it obvious that it is total bollocks. |
|
| |
The first pictures at the
Airfoil Lifting Force Misconception link are also bollocks. |
|
| |
Is it virtually impossible to get lift out of gyroscopic-type motion. |
|
| |
Sure, classical experiment, sit in swivel chair hold running gyroscope, turn gyro, chair turns, but trying to get the same effect for flight gets very pulling self-up-by-own-bootstraps very quickly. |
|
| |
As for D-Dalus rotary lift-system, that looks even naffer than most of my ideas..somebody please tell that man to give up, birds have wings for a very reason. |
|
| |
As a licensed pilot, I can't *even* begin to tell you how
wrong this is, and at so many levels. |
|
| |
Airflow, over a wing, is what generates lift. If it just
takes spinning wheels, then why don't we see flying
bicycles? Take a flying lesson and then say hello to Mr.
Daniel Bernoulli.
[- X 100] |
|
| |
Personally, I just think UP. I think I'm a few inches
off the ground right now. |
|
| |
Have you ever noticed how dentists wear lead-soled boots
to stop their high speed drills pulling them up into the air? |
|
| |
//The ground is irrelevant// |
|
| |
This is so true. If the ground were not there I would still be in the same place, but flying! Amazing stuff. |
|
| |
This all makes perfect sense, and is in fact the reason
yo-yos are banned from airplanes—the resulting
turbulence would shake the plane apart. |
|
| |
I'm amazed that the aerospace industry has made as far as
they have, given they're laboring under such a grave
misunderstanding of flight dynamics and basic physics. |
|
| |
The Wright brothers and Lawrance Hargrave are spinning
in their graves... and will soon take to the air again. |
|
| |
//thrust of the engines works by pulling on the air, not pushing off the ground |
|
| |
Having spent about a year faffing about with wing sections and fans, I can bring you the startling news - that things with wings fly more easily. |
|
| |
Because, wings work like lift accumulators as it's going down the runway, which means the engines don't have to be so big, so the plane doesn't have to be so heavy and so uses less fuel. |
|
| |
Sure, you can just use huge engines to make a plane go directly vertically up, but then you have huge engines, which are very heavy, so the plane is very heavy and you use a phenomenal amount of fuel. |
|
| |
This is the reason why large birds (which can actually fly) have wings. Mother nature has had x million years to work on it, so this is just trying to second-guess that. |
|
| |
No extra charge for this information. |
|
| |
Other large birds (of the flightless variety) just make themselves prone to feather-collectors/being eaten in some strange evolutionary way which makes no sense to our current science. |
|
| |
Of course, really big birds like emus, cassowaries and
ostriches have wheels, which they spin furiously, in order
to get airborne. |
|
| |
... and penguins, though technically they'd be called "paddlewheels". |
|
| |
Erm, watched all ten minutes of the D-Dalus video for 8 seconds of wobbly flight. Sure, it's early days but you could just make a lifter that works that well....oh, and nobody is running a rotor ship. |
|
| |
Forgive my pickiness, I am cold. |
|
| |
//elusive secret of how airplanes _really_ fly. |
|
| |
could you narrow that down a bit please, it's a long article... |
|
| |
I do seem to recollect someone posting a comment, upon hearing that the pope banged his head in a Mexican hotel, that some Secret Service agents had a similar problem in Latin America quite recently. |
|
| |
If airplanes were meant to fly they should have been covered with feathers. Why not use airplanes on our tried-and-true highway system like everybody else! Add headlights, tail lights and turn signals -- you're good to go. |
|
| |
<GROG thinking: "...I can't shake the feeling I missed something..."> |
|
| |
// could you narrow that down a bit please // |
|
| |
//they should have been covered with feathers. |
|
| |
Good idea, but seeing as it's your idea, you get the honour of the first test flight...no, no, no, I insist..after you...<starts gluing feathers onto a passing Dreamliner> |
|
| |
" No extra charge for this information."
LOL |
|
| |
Re: The "No tire spin needed" link. Check out the tires and wheels on that baby. You kNoW where that lift is coming from, especially with flaps up. |
|
| |
We-ell, the way I understand it, and the way
I've been taught, Bernoulli lift isn't the only lift an aircraft uses, and in fact for many cases aerodynamic lift (that generated from positive angle-of-attack) is the greater of the two. |
|
| |
And Magnus lift is a thing. Just not a very strong thing - ie not worth making an aircraft specifically for. |
|
| |
That's not to say that the idea isn't bollocks, but fair play. |
|
| |
Ha - I just read this and I'm giving it its first plus point for making me laugh out loud, especially the "eeek eeek" cure. Excellent. |
|
| |
I still don't understand how planes with skis and
pontoons fly without their wheels spinning. Did I miss
something in my flight classes? |
|
| |
// Bernoulli lift isn't the only lift an aircraft uses, and in fact for many cases aerodynamic lift (that generated from positive angle-of-attack) is the greater of the two.// |
|
| |
That's a meaningless distinction; it's like saying that a car partly accelerates partly due to friction between the tyres and the road, but mostly due to Newtonian reaction. Aerodynamic lift _is_ Bernoulli lift; Bernoulli's laws simply describe the relationship between pressure and velocity in a constant-energy flow field (which a subsonic wing closely approximates). Lift is generated entirely by the Bernoulli effect, and entirely by the angle of attack. |
|
| |
How about I just repeat myself - the qualifier there was - "the way I was taught". I'm only a paraglider pilot, not a real one - but in our course the concepts were segregated, possibly just for simplicity's sake. The focus there being an aerofoil with zero angle of attack can product lift due to the aerofoil shape, whereas a flat wing can't. However a flat wing with positive angle of attack can produce lift, as will an aerofoil with +ve AOA. Therefore, at least conceptually, you can keep the concepts separate. As a mechanical engineer myself, thinking back - I suggest that the instructor was describing an empirical model that's easier to understand, but matches the situation closely enought to be useful. I'ts no good trying to teach 4th order differential equations to a group that includes dope smoking hippies... |
|
| |
Fair enough. It partly depends on how angle of attack is defined (geometrically, or empirically as the angle of zero lift); some curved wings produce lift for some definitions of zero angle of attack. |
|
| |
But there is no real distinction between the way that a flat wing and any other profile wing produces lift. Its just that better aerofoils are more effective (provide more lift) and are more efficient (produce less drag). As the second link points out, the *trailing edge* of any wing, flat or otherwise, must have a positive angle of attack for lift to be produced. All wings produce lift by imparting downwards momentum to the air they pass through, that is, by deflecting air such that it has a downwards velocity component when it leaves the trailing edge. All wings have a positive angle of attack relative to the angle of zero lift. |
|
| |
If I were teaching such a course, I would not segregate the concepts like that. Instead, I would explain that any flattish object with a positive angle of attack (relative to the angle of zero lift) produces lift by deflecting air downwards, then explain why some objects (good lifting aerofoils) do so better than others. |
|
| |
[Sunstone], when you're done posting a zillion links to
illustrate the same half thought-out point, go for a drive
and stick your hand out the window, held out flat and palm
down. Now tip it back so that your thumb is the top of the
incline. You should be feeling an aerodynamic force that
those craa-aaazy engineers call 'lift'. It's what causes
airplanes to go up in the air. If you want to build a lot of
lift very quickly, it helps to tip the whole damn airplane
back rather than just rely on the control surfaces. This
creates a great deal of drag in the trade-off, which is why
only ludicrously powerful airplanes like fighter jets loaded
into catapults do it. It's fairly common knowledge. |
|
| |
Now stick your head out the window--preferably while
approaching a tunnel. |
|
| |
//Now tip it back so that your thumb is the top of
the
incline. You should be feeling an aerodynamic force
that those craa-aaazy engineers call 'lift'.// |
|
| |
Sorry, but that's completely wrong. It's actually
caused
by gyroscopic precession from the car's wheels. It's
the same force that causes 18-wheelers to lift
completely off the ground at high speeds, which is
why you often see truck speed limits lower than those
for general traffic. |
|
| |
I say this is a great idea for landing truthers at their
next convention (in Iran?) with this technology. |
|
| |
Funny, just after reading this ... idea ... I stumbled on the Kickstarter at [link] |
|
| |
My fault that the video segment I posted was not complete. I can't locate online this full episode of Mythbusters, only the last part of the conveyor belt segment showing that a plane will take off on a conveyor belt with no mention the plane was off the ground quicker when on the conveyor belt and had a longer takeoff roll when off the conveyor belt? Can anyone confirm the plane lifted off faster when on the belt? Thank you |
|
| |
The plane will take off from a conveyor belt, but it will be
moving forward when it does so. And, relative to the
ground outside of the conveyor belt, will have exactly the
same take-off roll as the plane without the conveyor
belt. |
|
| |
The basic problem with this argument is a flaw in the
problem statement. A car is driven by it's wheels. So if
the surface underneath the car is going backwards at the
same speed the car is attempting to go forwards, the car
will not move. The relative motion between the car and
the ground matters. |
|
| |
However, an airplane is driven by the air it pushes
backwards (by prop or jet). As a result, even if the
surface underneath it is moving backwards, that doesn't
affect the driving mechanism, so the plane still moves
forwards, and the wheels just spin twice as fast. It would
also be possible to get an airplane to take off with the
wheels not moving at all if you ran the conveyor in the
direction the plane is trying to move. In this case, it's the
interaction between the plane and the air, not the plane
and the ground (or belt) that matters. |
|
| |
The equivalent to a conveyor belt under a car would be a
wind-tunnel past the airplane (i.e. the driving medium is
moving past the vehicle instead of the vehicle past the
driving medium). And in that situation, the plane can lift
off, because the speed of the air over the wings is the
same as it would be if the plane were in still air speeding
down a runway. Of course if the plane exited the high
speed air stream without any forward momentum, then
there would be a problem. |
|
| |
Now for the second part of the magical secret of spinning wheel lift:
Looking at the wheel from the side of the airplane, the tire has a curvature, just like a conventional wing does, on the top and bottom and everywhere else. The tires act as wings just like a fully symmetrical airfoil with curves on the bottom and top does. The bigger the tires, the more lift, just like on the fast takeoff bush planes Klaatu mentions. |
|
| |
Due to the Magnus effect, wheels produce lift in the downward direction, in other words, the opposite of upward. |
|
| |
Re your first link today: Of course flat wings work. Grab a piece of cardboard and swing it around at an angle.
Properly shaped wings just work better. |
|
| |
Re your edit on 2016-02-28: The horizontal stabilizer on a plane's tail is usually configured to produce downward
lift, to counteract the downward pitching moment produced by the airfoil shape of the main wings. |
|
| |
Excellent point: I still don't understand how planes with skis and pontoons fly without their wheels spinning. Did I miss something in my flight classes?
— Klaatu, Mar 08 2013 |
|
| |
A: The propeller(s) or jet turbines and navigation gyroscopes compensate for the loss. |
|
| |
[Sunstone] - My respect for your determination! |
|
| |
I’m afraid that I agree with the majority view
here, spinning wheels will not make a noticeable
difference to the lift required to get a plane off
the ground. |
|
| |
I would point out that quite a few people here are
engineers/have studied aerodynamics at university,
or are pilots. So you’re getting some well-
supported views (I.e. supported by experimental
evidence and personal experience) |
|
| |
The whole “that’s not really how a wing
works/Bernoulli equation” argument is really
about how the physics is actually quite complex,
but the simplifications made in teaching the
subject skip over some of the detail. It’s not that
the science is wrong. |
|
| |
Rereading my earlier anno, I thought I had gotten the Magnus effect backward. But I went to Wikipedia to check, and I got it right
[link]: |
|
| |
// Topspin in ball games is defined as spin about a horizontal axis perpendicular to the direction of travel that moves the top
surface of the ball in the direction of travel. Under the Magnus effect, topspin produces a downward swerve of a moving ball,
greater than would be produced by gravity alone. Backspin produces an upwards force that prolongs the flight of a moving ball.
// |
|
| |
Also, fun fact: while the effect is named after Magnus, the lift generated is named after Kutta and Joukowski. |
|
| |
This applies to boats, fans helicopters, anything with blades:
Consider that with the wide leading and trailing edges of the blades are placed in a "0 pitch" position, 90 degrees perpendicular to the fuselage, the leading or trailing edge is furthest from the fuselage, you get maximum thrust.
As pitch is increased -- the leading edge of the propeller moves towards the the direction of flight and trailing edge moves toward the rear of the craft -- thrust is reduced.
This is why an airfoil is necessary to create thrust : o I |
|
| |
Likewise, when an airplane is flying the wing flaps are always in a down position to disturb the airflow over the airfoil and decrease excessive lift.
During takeoff and landing flaps are up to allow maximum lift by allowing a clean flow of air over the airfoil ; - D |
|
| |
Helicopter rotors, fans and boat propellers share the same traits. |
|
| |
"Now stick your head out the window--preferably while approaching a tunnel.
— Alterother, Oct 17 2013" |
|
| |
//when an airplane is flying the wing flaps are always in a
down position to disturb the airflow over the airfoil and
decrease excessive lift. During takeoff and landing flaps are
up to allow maximum lift by allowing a clean flow of air
over the airfoil //
Um.
Have you ever actually watched a plane fly? Been on one,
and looked out the window, perhaps? |
|
| |
// This applies to boats, fans helicopters, anything with blades: Consider that with the wide leading and trailing
edges of the blades are placed in a "0 pitch" position, 90 degrees perpendicular to the fuselage, the leading or
trailing edge is furthest from the fuselage, you get maximum thrust. As pitch is increased -- the leading edge of the
propeller moves towards the the direction of flight and trailing edge moves toward the rear of the craft -- thrust is
reduced. This is why an airfoil is necessary to create thrust : o I // |
|
| |
I can't judge whether what you said makes any sense (though I suspect it doesn't), because I can't tell what you
mean by it. Could you rephrase it? |
|
| |
// Likewise, when an airplane is flying the wing flaps are always in a down position to disturb the airflow over the
airfoil and decrease excessive lift. During takeoff and landing flaps are up to allow maximum lift by allowing a
clean flow of air over the airfoil ; - D // |
|
| |
I now get the impression that you're trying to make some kind of joke…? |
|
| |
What [Klaatu] said, word for word. |
|
| |
I was always tripped up by the airplane on a treadmill question because from the first time I heard it I considered the wind induced by the movement of the treadmill and the additional drag of the wheels. Then according to the questioner getting the "wrong" answer meant I didn't understand flight dynamics. (or basic physics for that matter) |
|
| |
Don't stress yourself over flight dynamics or fluid flows ... concentrate on the things you really need to master, like using your opposable thumb properly, and bipedal locomotion .... |
|
| |
Although, a plane could be spun up via a wire cable anchor point in one of the wings. Or, with a good energy source, an airport with it's own wind. Both would get wing to air interaction. |
|
| |
// spun up via a wire cable anchor point in one of the wings. // |
|
| |
Do you mean "circling a central pivot until it has sufficient airspeed to fly" ? |
|
| |
Let's put some numbers on that ... |
|
| |
Assume an all-up takeoff mass of 100 tonnes, and a minumum forward speed of 300 km/h for V2. Allow a constrained cable length of 200m. |
|
| |
So, class, we have a mass of 100,000 kg, moving at 300 km/h, on a 200m radius. |
|
| |
What is the angular velocity of the craft, and what is the tensional force in the cable ? You may neglect the mass of the cable itself, assume that the pivot is frictionless, and the thrust of the engines is always tangential to the circumference. |
|
| |
Write on both sides of the paper. Show your working. |
|
| |
No, [Voice], you should have gone earlier when you had the chance. If you make a mess, you'll clean it up yourself. |
|
| |
Centripetal force = m(sqr(v)/r)
= 100000x83.33x83.33/200 = 3472200N = 3.4MN |
|
| |
Tension has to hold centripetal force so
3.4MN is 781000 lbs, strongest cable currently 17kN,3822lbs, carrier arresting cable 215,000lbs |
|
| |
Choose the cartoon one, the Airport with a bank of fixed jet engines seems more plausible. |
|
| |
You may award yourself a silver Class Star. |
|
| |
//clean it up yourself.// |
|
| |
You're not the boss of me! |
|
| |
//we have a mass of 100,000 kg, moving at 300 km/h, on a 200m radius. |
|
| |
What is the angular velocity of the craft, // |
|
| |
0.06631, and thank Tesla for online calculators |
|
| |
//and what is the tensional force in the cable ?// |
|
| |
Assuming a massless, spherical cable of uniform density in a vacuum in deep space where there is no gravity and in an alternative universe where we get to ignore both the speed of light and the angular difference from actually rotating off axis from the central point, it's the same as centerpetal force, or about 3.5 million newtons. Thank Babbage for online calculators. Now give me my pudding! |
|
| |
My due was to Hyperphysics and some background Wikipedia. So a dull silver star for not including credits. |
|
| |
You got a silver star. [Voice] gets a bucket and mop and has to sit in damp underwear until home time, plus becomes the target of ridicule and humiliating isolation. |
|
| |
You did pretty well, on balance. |
|
| |