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 A1_GOLD
Joined: 5/6/2009
Msg: 68
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How do airplanes fly?Page 6 of 7    (1, 2, 3, 4, 5, 6, 7)
In the US and most other countries only if your licensed, inspected, certified and have filed a proper flight plan.. If you tried to fly an airplane without all that you face going to jail for a long time and a stiff fine too.
 2findU
Joined: 11/19/2005
Msg: 71
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How do airplanes fly?
Posted: 12/21/2009 3:25:50 PM

Ah, the old Bernouli vs Newton creates wing lift debate. Why can't it be BOTH? Just because a flat wing works does not disprove Bernouli's theorem's relevance to the creation of lift. A flat wing just has to be tilted up more in relation to the oncoming air (higher angle of attack). It is often installed on the model plane with an appreciable angle of attack (angle of incidence).

The oncoming air STILL has to travel a greater distance over the top of a flat wing when it has enough angle of attack-- and it needs enough angle of attack to create lift. This is how ALL wings are able to fly upside down, too, btw. One could make a barn door fly with enough thrust and the needed angle of attack.


In fact if you have ever seen R/C model planes many of the non-scale planes have horizontal and vertical stabilizers that are flat and not airfoil shaped. Frankly, enough horsepower and speed will get anything airborne. That's why race cars have to invert their "lift" into downforce.
 A1_GOLD
Joined: 5/6/2009
Msg: 72
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How do airplanes fly?
Posted: 12/22/2009 1:35:33 PM


I dont know if ultra lights qualify as an airplane but you can build one and not need a civilian aviators certificate and fly one


LOL!!!

OK, OK,
I was told that airplanes fly because of Archimedes Principle. Just like a cork in a glass of water an airplane floats up in dense air. It simply works for every possible scenario.
When the air has a density less than the flying object, it falls. Works the same with hot air balloons, gas filled balloons, helicopters, airplanes, gliders, birds, insects and lifting bodies.
Use any other principle of physics, the forces don't add up, it sounds like magic is applied.
EUREKA!

Here, try it out;
The air passing over the airplanes wing got so dense the airplane began to float up in it.
The air around the balloon was denser so he balloon floated up.
The propellers made the air much denser so the helicopter floated up.
It's so easy!

javascript:smilie('')
 aremeself
Joined: 12/31/2008
Msg: 74
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How do airplanes fly?
Posted: 12/22/2009 9:27:42 PM
santa operates in a different dimension, or how could he deliver all that cra, I mean stuff in a few hours?
 A1_GOLD
Joined: 5/6/2009
Msg: 80
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How do airplanes fly?
Posted: 12/29/2009 7:43:15 PM

Who told you that? Archimedes' principle doesn't keep airplanes up. Aerodynamic lift is completely different from bouyancy. Airplanes are known as heavier-than-air craft, and that distinguishes them from balloons.


Finally somebody read my post!
OK smart guy, you don't get off so easily.
My explanation covers planes flying sideways and upside down, can yours?
If you find my explanation so difficult to believe explain yours to me.
One condition: You may not use Bernoulli, using Bernoulli a Piper Cub would have to travel well over 400 miles an hour at takeoff to get enough lift to become airborne. I can offer citations explaining why Bernoulli fails if you wish.
I would offer a second condition, cite the Newtonian Laws you are using, you don't have to but it would earn my respect.
 flyguy51
Joined: 8/11/2005
Msg: 82
How do airplanes fly?
Posted: 12/30/2009 2:40:31 PM

My explanation covers planes flying sideways and upside down, can yours?
If you find my explanation so difficult to believe explain yours to me.
One condition: You may not use Bernoulli, using Bernoulli a Piper Cub would have to travel well over 400 miles an hour at takeoff to get enough lift to become airborne. I can offer citations explaining why Bernoulli fails if you wish.
I would offer a second condition, cite the Newtonian Laws you are using, you don't have to but it would earn my respect.

As has been said, your explanation does not cover airplanes at all. As has been said, it rather covers lighter than air craft (helium balloons, hot air ballongs, blimps, dirigibles).

Put simply, an aircraft airfoil accelerates air and deflects it downward. Using Newton's third law of motion, that downward flow causes an upward force on the airfoil-- lift.

Airplane sideways: now the aircraft fuselage is acting as an airfoil and is deflecting air downward. Note how aircraft flying sideways are tilted up (high angle of attack), and they cannot fly this way very well at all (inefficient airfoil).

Airplane upside down: while less efficient (the degree of inefficiency depends upon the airfoil shape and angle of incidence), the wing will still create lift through a positive angle of attack, which deflects air downwards.
 flyguy51
Joined: 8/11/2005
Msg: 84
How do airplanes fly?
Posted: 12/30/2009 5:34:50 PM

Dozens of ducted fan, tilt rotor, tilt wing etc.

Actually, these all utilize airfoils and produce aerodynamic lift, so it is not so much peripheral to the topic as it is redundant.
 60to70
Joined: 7/28/2008
Msg: 85
How do airplanes fly?
Posted: 1/1/2010 12:21:27 AM
Do airplanes fly with a wing and a prayer. Airplanes are an illusion wrapped in an enigma, flushed out by a shortage of nothing short of being a wondrous rush in the way we travel. Will that do.
 A1_GOLD
Joined: 5/6/2009
Msg: 86
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How do airplanes fly?
Posted: 1/1/2010 7:28:06 AM

Put simply, an aircraft airfoil accelerates air and deflects it downward. Using Newton's third law of motion, that downward flow causes an upward force on the airfoil-- lift.


Your saying that the air under the wings go down like a rockets exhaust? For every action there is an equal and opposite reaction. That makes sense and would explain the thrust developed by the airplanes engines if they were pointed downwards but how do the wings do that?

I know that the way birds develop upward thrust is by flapping their wings, pushing air down, a third law phenomenon, but airplanes don't do that, flap their wings that is.

I've been looking for wind tunnel evidence of it for years! Something that shows the air deflected downwards under the wing. Could you direct me to an online video source that does please.
 flyguy51
Joined: 8/11/2005
Msg: 89
How do airplanes fly?
Posted: 1/1/2010 12:55:56 PM

Your saying that the air under the wings go down like a rockets exhaust? For every action there is an equal and opposite reaction. That makes sense and would explain the thrust developed by the airplanes engines if they were pointed downwards but how do the wings do that?

Not exactly. I'm saying that the air OVER the wing flows at a downward angle at the trailing edge of the wing. The faster the air moves, the less downward angle it needs to create lift in the amount required. That is why an airplane flying quickly is level to the ground, while the same plane flying slowly (fast/slow relative to that airplane) is tilted up relative to the ground-- or, more accurately, relative to the oncoming air-- i.e. angle of attack.

Why would the wings need to flap? If the plane is moving forward due to the engines force, this causes the air force to go under the wing pushing the plane up due to the angle of the wing.

Close, but it is the air going over, not under, the wing that is lifting the plane.
 flyguy51
Joined: 8/11/2005
Msg: 91
How do airplanes fly?
Posted: 1/1/2010 4:00:34 PM

Wellll really isn't it a reaction of both? You know the air below is creating a force as well as the air above the wing.

Yes, but it isn't a force that is beneficial to lift. I think you are working more along the lines of a parachute or airbrake, where air impacting a surface creates a slowing force. Ideally, a wing would work best if air only flowed over the top, but that cannot happen. It would also work best if it were infinitely long, as drag is created where the upper and lower flows meet at the wingtips.

Using Newton's 3rd law again, the flow under the wing lessens the downwash coming from the top.

Using Bernouli's Principle ("nooo!"), the air flowing underneath lessens the pressure differential being created.
 Island home
Joined: 7/5/2009
Msg: 100
How do airplanes fly?
Posted: 1/4/2010 6:34:17 PM
Without top we have no bottom without bottom we have no top

If you have no sides and turn it on it from horizontal to vertical you will have no top and no bottom and then perhaps need to choose which side your on.
Not sure if this helps with flying upside down.
maybe more about flying side on?

Just saying

aaamm
you cheat by floating
when you are denser than air
by walking on sunshine
and you do it so well
 flyguy51
Joined: 8/11/2005
Msg: 105
How do airplanes fly?
Posted: 1/6/2010 4:43:40 PM
Appreciative, I am admittedly just a relative layman without a degree in aeronautical engineering, so I have the following questions/issues about what you are saying:

The air under the wing is pushing up on it, by pressure above atmospheric pressure

It is my understanding that the flow below the wing is below atmospheric pressure, and the flow above is even farther below atmospheric pressure. To tell you the truth, though, I never thought about where that pressure rates relative to atmospheric.

if the wing is concave below, of has positive angle of attack, then the air deflected by the wing's lower surface adds to the downwash (and the lift).

I didn't think that the boundary layer adheres to a concave surface. I would be interested to see pictorial or textual sources of this happening with a concave wing.

it would be reasonable to say that a speed-change causes a pressure change, a la Bernoulli's effect.

Where so many posters here, and so many books too, are wrong is where they say that, over the wing, Bernoulli's principle is causing the low pressure. No, above the wing, the low pressure is causing the high speed, via Bernoulli's principle, not the other way around.

The claims of these two paragraphs contradict eachother. Regardless, I would be interested in seeing cites that you feel are correct in explaining the true principle.
 A1_GOLD
Joined: 5/6/2009
Msg: 107
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How do airplanes fly?
Posted: 1/7/2010 7:09:51 AM

That's not buoyancy, that's called a hurricane.


Now that's what you call Air Power!

I must thank you all. I had forgotten that once upon a time I had wanted to be a pilot. Absolutely fascinated by Rutan designed home built planes in the 70s. Can't find anything as exciting now as his Quickie (Model 54) or EZ. Sweet stable exciting machines something to make you look forward to a calm Spring or Summer day's outing.

Is there anything as exciting out there now? A little airplane a couple of people can build over the Winter?
 A1_GOLD
Joined: 5/6/2009
Msg: 119
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How do airplanes fly?
Posted: 1/11/2010 7:58:02 PM
All the discussion of spy planes got me thinking.

James May, a British TV reporter, recently narrated a show called "James May on the Moon". Within the show he boards a U2 'NASA' spyplane and flies in it to 70,000 feet. I've never seen anything quite as beautiful concerning flight. You might look it up on YouTube as "Ride on a U2 spy plane". It puts flying to edge of space in good context.

I've never seen anything like it.
 Island home
Joined: 7/5/2009
Msg: 129
How do airplanes fly?
Posted: 1/20/2010 9:21:29 PM

How do airplanes fly?


Extremely well
Compared to a rock
 A1_GOLD
Joined: 5/6/2009
Msg: 130
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How do airplanes fly?
Posted: 1/21/2010 7:23:04 AM
Have you seen Avatar? Those rocks flew very well.
 quietcowboy
Joined: 12/25/2007
Msg: 137
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How do airplanes fly?
Posted: 2/25/2010 5:38:57 PM

People are sometimes afraid to fly when it is raining or foggy out but those are the best days to fly....


The best days for highest lift during take-off are cold & dry - air is more dense. Humidity or water vapor is less dense than air.
 bestspfx
Joined: 8/31/2011
Msg: 140
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How do airplanes fly?
Posted: 11/15/2011 4:40:40 PM
Doesn't this just plain work because the air moves faster over the top of the wing creating a lowering of the air pressure pushing down on the wing. That means the air pressure on the underside of the wings is higher resulting in a push up on the wings. So for example there are 14lbs per square inch pushing up on the botton of the wings while only for arguments sake 10lbs per square inch pushing down, effectively resulting in enough per square inch pressure pushing up in the offset to lift the entire weight of the aircraft up. Obviously it is only achieved by the aircraft moving forward to cause air to rush over and around the wing which is why thrust forward is need by the engines. This effectively achieves forward motion needed for travel while the design for the wings creates the conditions for the aircraft to be lifted. And the other reason I have heard for an aircrafts forward motion is basically the same. The ignition and resultant speed of ignited gas particles leaving the back of an aircrafts engine results in a low pressure area right there, the surrounding air in earths atmosphere surrounding the aircraft under 14lbs per square inch rushes in to that low pressure area and effectively pushes the aircraft forward. This argument makes the most sense to me. So it is a simple physics argument harnessing the existing force of 14lbs per square inch of air pressure and putting it to work for us in various ways. This argument seems to make the most sense to me although I am no physicist or expert by any stretch. The mystery to me has always been, if there is one, how do you achieve thrust motion in space if this is the actuality here on earth in an atmosphere under pressure. What are the forces allowing for that with 'no pressure' conditions existing? Is it really that law 'every action results in an equal but opposite reaction'? Thats the one I have a hard time buying. But then again, I don't have a vaacuum handy to do an experiment in! Lol
 cbbull21
Joined: 3/9/2009
Msg: 141
How do airplanes fly?
Posted: 11/15/2011 7:26:27 PM
Suction? Pull?
Umm.....no there are no such things.
What you might refer to as suction is fluid flow or a difference in flow/pressure.
(Pulling is just a net force due to 'pushing' asymmetrically. )
I don't think I need to reiterate why the net force is on the side of laminar flow, or propellers working by conservation of momentum.
 Bishopboat
Joined: 9/3/2010
Msg: 142
How do airplanes fly?
Posted: 11/18/2011 6:47:47 AM
In a nut shell we have a a leading edge and a tailing edge of a wing. the leading edge of the wing seperates air into a low pressure spot on top and a high pressure spot on the bottom and they meet back together at the tailing edge. This area of high pressure and low pressure means that the denser air molecules on the bottom of the wing want to "mate up" with the "less dense" air molecules on the top of the wing. If enough thrust is applied a greater differnce is created, with enough air flowing on the top and the bottom (air speed) the "lift" effect of the denser air molecules wanting to meet up will cause the aircraft to lift up (flight). That's bacicly flight for retards, not diving into air foils, bernoulli's principle, etc...

I say this as an A&P mechanic...
 Miick
Joined: 7/16/2009
Msg: 143
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How do airplanes fly?
Posted: 11/20/2011 4:54:07 PM
You have described an aerofoil, Where the air is contorted into creating differential pressures on either of its sides.

Many different forms of aerofoil exist, and all have different implications, advantages, and disadvantages; Flat , flat bottomed, hollow, symetrical, semi-symetrical, and so on.

Most airliners use semi-symetrical, whereas most ultralights use flat bottomed, or flat.

Most Aerobatic aircraft and close to all helicopters use full symetrical.

The deflection of air accounts for around 17% (if i remember correctly) of the lift that an aerofoil produces, most is produced by the differing pressures. Keep in mind that induced airflow is a result of this, yet air will always flow from high pressure to low pressure, so around blade tips and wing tips you have a reverse flow.

The lift formula is

Lift = CL X 1/2p X V^2 X S

where CL represents the shape and angle of the aerofoil, p = the density of the fluid (which changes with altitude, pressure, humidity, and temp.), S is the surface area of the aerofoil, and V^2 is the velocity. A double of airspeed will quadruple lift. The same formula is used to calculate drag except CL is replaced with CD and 'lift' is replaced with 'drag'.

Placing the aerofoil at an angle relative to the oncoming airflow (blade angle), will create your induced flow, up, then downward to follow the contour of the aerofoil, the downward componant of airflow (induced flow) combined with the oncoming airflow (airflow due to velocity) creates a Relative airflow to the blade/wing. The angle between the direction of relative airflow and the chordline (centre line) of the wing creates your angle of attack, which i mentioned earlier. The greater the angle of attack, the more you will be manipulating the differential air pressures. Where the airflow that will meet up with the underside of an angled wing will be slowed down (relative to the wing), its pressure will increase, whilst the air across the top surface of the wing is accelerated along its surface, its pressure is decreased.

All this really comes back to is Bernoulli theorum which has been discussed earlier, and is very easily demonstrated by driving down the motorway and sticking your hand out the window, with your palm vertical, you feel the push of the oncoming wind. Relative to you, you are slowing that wind down to a stop, taking away its kinetic energy. Its total energy will remain unchanged unless you slow down, so as a result its pressure energy increases, which you feel as drag or resistance on your hand.

I say this as a dual rated pilot (helicopters and airplanes), so if there is anything else you are curious about, let me know, similarly if anyone has any corrections to make..

I was gonna get on to the different types of aerofoils and their applications but i cant be bothered now.
 MikeWM
Joined: 2/7/2011
Msg: 144
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How do airplanes fly?
Posted: 11/20/2011 5:28:35 PM
I actually love sticking my hand out the window at speeds past 70mph on a warm day

The drag when you move your hand from the horizontal position is pretty severe

When was younger I did jujitsu and one day a week we used to train and spar at the swimming baths in water up to our necks for reasons that are fairly similar to this in some areas as water makes you more aware of drag and altering a strike technique to reduce the drag as well as improving counterbalance and reducing overbalance

Theres some interesting documentaries about that go into the problems and technical challenges faced when the first jet planes were being produced as the wings were one of the most important and most limiting aspects of early designs

I cant remember much of the tech speak as its not an area I have any specialisation in whatsoever, but for the people who are interested in it searching out those documentaries would probably be pretty interesting and informative
 Kohmelo
Joined: 9/20/2011
Msg: 145
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How do airplanes fly?
Posted: 11/20/2011 7:00:51 PM


The mystery to me has always been, if there is one, how do you achieve thrust motion in space if this is the actuality here on earth in an atmosphere under pressure. What are the forces allowing for that with 'no pressure' conditions existing? Is it really that law 'every action results in an equal but opposite reaction'? Thats the one I have a hard time buying. But then again, I don't have a vaacuum handy to do an experiment in! Lol


That's easy. It's exactly what you said, so when you burn some fuel and exhaust it into space, the ship forces the exhaust out and the exhaust forces the ship forwards or whatever direction is needed, equally and opposite to the original force.
Even better, in spaced you don't have to deal with air resistance and the force of gravity is much less, so the forces stopping you are far less as well.
Its actually easier than how planes work, and far more fuel efficient.

I don't know why you think an atmosphere or pressure is required. but if you want to build one just google it, there's some good instructions out there
 Bishopboat
Joined: 9/3/2010
Msg: 146
How do airplanes fly?
Posted: 11/21/2011 12:42:22 PM

You have described an aerofoil, Where the air is contorted into creating differential pressures on either of its sides.


Damn, that's text book!
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