My 4 year old niece asked me this question sad to say i was dumbfounded on how to explain it to her. I just told her it's all about the wings... Does anybody have a better answer than me? :sad:

OK, I have to ask...
This forum attracts aviation enthusiasts. Some are spotters, some are highly trained pilots, engineers, some are PAX. I would think that with that level of interest you would know the basic principles of flight. Not trying to mock you, I am just curious how come you don't know.

As for a simple explanation, the wing has a longer surface on top, than on the bottom. When air travels over those two surfaces at the same speed, it creates a negative pressure on top, sort of a vacuum cleaner effect and keeps the wing in the air.

I am sure many will come soon to give a better explanation...

With due respect Dushan, I think what powerstall meant was how does one explain aerodynamics to a 4 year old, not to say he doesn't understand himself.

OK, I guess I misunderstood. Sorry.

I was about 6 when my uncle gave me the explanation I posted, He drew some pictures, though. Maybe 4 is too young...

Just tell her what I told my kids.

Two angels carry the plane into the air and if any children on the plane misbehave, they will let go.

The only way to prevent misbehaving kids inflight.

And any accusations that the therapy they are currently having is my responsibility in any way shape or form, is completely rejected!

His explanation wasn't very clear Dushan, It made me smile when I first read it I must admit, then it dawned on me what he was getting at. ;)

Wings are important but don't the engines play a small part...:D

I'm looking forward to someone being able to present the answer in terms a four-year-old can understand. Might work for me too.

A trip to a flight museum might help. One of the museums I belong to has a kid's corner with a great interactive display devoted to this exact question. They also have a colouring book which is very basic when it comes to explaining the mechanics. Most museums have an educational/interactive place for kids.

Oh....try the library too. I have seen many books for all ages devoted to
flight.

Answer to a four year old?



Magic. :ok:

Magic.

Reluctant737, I love that!!!!

The flight fairy sprinkles stardust on the wings, and that is how an airplane flies.

Now, when it comes to taking the written exam for my PPL, do you think that will "fly" with the examiners? I think I'll try it. Heck, what can happen? I can always take it again.

Powerstall

I thought your question was quite clear. The flight miseum is a good idea, I don't know where you live but for those in England now the RAF Museum at Hendon is a superb faciility with a great kids educational area. Alternatively, a fun solution is getting kids of 4 or 5 sitting behind you on your bike putting their arms out and seeing how the wind catches their hands when they turn them a little and lifts them up, or you can get them to use bits of card stuck on lollypop sticks (means you can tell them if they want to learn they have to start by eating an icecream first!), then ride down a hill, or use a fan in the house if you have one or even a hair dryer.


oh I love the Magic bit as well. Before launching off down the hill on your bike, instead of shouting 'Geronimo' you could get them to shout 'Abra Cadabra'

@<hidden> I agree, the museum at Hendon is a superb resource. :ok:

She may be four but she deserves better than the kind of rubbish that most PPLs spout about flight.

You must as well start as you would have her finish. Start with a basic explanation of Newton's 3rd Law and then gently move on from there, otherwise she'll end up doing do what most pilots do and be mumbling some incantation about Bernoulli and a witches hubble bubble or two by the time she gets her PPL at 16.

Kids are very receptive to the truth and simple explanations of the correct phenomena at an early age will quickly lead to more and more pertinent and complex questions. By the time she's six you'll find yourself explaining the Coanda effect and by 8 she (and you) will be grappling with Newton's second law and Navier-Stokes equations.

NASA has some great resources and even the more complex interactive ones still get kids rapt attention.

Beginner's Guide to Aerodynamics (http://www.grc.nasa.gov/WWW/K-12/airplane/bga.html)

Have fun, it will be a delightful flight. It was only when I started to explain to a kid how planes flew and started to deal with the huge intelligence of the questions that I was asked that I actually realised how little I really knew. :)

It was only when I started to explain to a kid how planes flew and started to deal with the huge intelligence of the questions that I was asked that I actually realised how little I really knew.

I have the same problem when asked, "How are babies made?" :O

I have the same problem when asked, "How are babies made?" http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/embarass.gif

V2, my answer to that is based upon my own sure knowledge.

http://www.eatlocal.org/newsletter/2009/january/baby_stork.jpg

And I thought it had something to do with a cabbage patch.

http://imagecache2.allposters.com/images/pic/EUR/1500-3070~Cabbage-Kids-Posters.jpg

The flight fairy sprinkles stardust on the wings, and that is how an airplane flies.
...And, if you don't believe that, then tell them after sprinkling the stardust, they then go & work in the galley!!!

When air travels over those two surfaces at the same speed, it creates a negative pressure on top, sort of a vacuum cleaner effect and keeps the wing in the air.

Unless, of course, you're on a conveyor belt...

@<hidden>

That may be the way they do it in your part of the world!:eek:

How does an airplane fly?

Money, and lots of it.

Quote.:As for a simple explanation, the wing has a longer surface on top, than on the bottom. When air travels over those two surfaces at the same speed, it creates a negative pressure on top, sort of a vacuum cleaner effect and keeps the wing in the air.
:confused:Fine . How does the wing then fly upside down? I have no answer by the way.

Fine . How does the wing then fly upside down? I have no answer by the way


Only a fraction of the lift is actually produced by Bernoulli's subtle sucking.

The majority of the lift is still produced by the deflection of a large amount of air downwards and the application of Newton's 3rd Law (angle of incidence, angle of attack blah, blah, blah).

Look at the shape of an aerobatic aircraft's wing and you will see that many are designed so that Bernoulli's subtle sucking occurs on both sides of the aerofoil thereby increasing efficiency when the aircraft is flying inverted although this is not necessary for inverted flying.


(And they say that aerodynamics isn't sexy).

http://www.iop.org/EJ/article/0031-9120/38/6/001/pe3_6_001.pdf?request-id=cbabde42-24b4-48be-9fea-3493bf176ea1

Even more accessible and talks about why if we just accept the Bernoulli explanation, as some PPL manuals do, for flight then inverted flight would be problematic.

http://home.fnal.gov/~dcc/lift.pdf

http://www.pprune.org/private-flying/250749-inverted-flight.html

Lift Pixies and conveyor belts.

Don't underestimate a four year old. Start in with the basics and then just keep answering the questions. Explaining a venturi is pretty easy when it's on paper.
Then go to half a venturi and a day or two later she'll probably be asking about the angle of incidence of the compressor vanes.

Paper planes can be great fun as well.

It's the lift arrows. Look at any picture of a wing in an aerodynamics book and there are lots of little arrows on top pointing upwards pulling and lots of little arrows pushing from underneath. There is one big arrow (gravity) pointing down. When all the little arrows exactly make up the big gravity arrow the plane flies level. When they don't the plane climbs or descends as appropriate. Sometimes all the little arrows fall off together. This results in a hard landing.

What I don't understand, is how come you don't see the arrows on the real thing.

Whilst we're on the subject, how do they get the power to the wheels for taxying and take off? There doesn't appear to be any drive mechanism.

And don't get kids onto how helicopters fly!

Just use the ugly and earth repulsion theory. :)

Sorry Michael but as a 4 year old myself I will:
A helicopter alters the angle of attack of all it's blades collectively and with the lever fully down the blades sit at perhaps 1 or 2 degrees. This is for minimum drag in autorotation but is still a positive angle of attack.
How then can (some) fly inverted???? :confused: Particularly r/c models that hover all day inverted.
Now that's magic! :cool:

Wings are important but don't the engines play a small part...

You can fly without engines, you can't fly without wings...being an erstwhile glider pilot, I would say that, wouldn't I?

There are two lift pixies; one is called Bernoulli and the other is called Coanda.
Their followers fight with one another and the faster the aeroplane goes on the ground the more furiously they fight.
Eventually Bernoulli and Coanda, who actually agree with each other, get fed up with the row and lift the aeroplane off the ground.
Their belligerent supporters now stop fighting and go to Jet Blast instead.

Well that's what I was taught at RAF Leeming - honest! :ok:

Answering a four old on this technical subject is best done by demonstration. Get a piece of flat cardboard and let them swing it edgeways to see that it doesn't do anything. Then bend it into a curve and let them try again. Once they have felt the lifting force, use a pencil and paper to draw the airflow diagrams. It worked for our little ones anyway. I reckon all the good questions come at around the age of four.

Why do we have bogies?
Where did the baby mice in the cupboard go? Why?
Why did the dead cat smell so bad?
What are testicles?
Why don't I have a willy like Edward?

Tell her the truth; Skyhooks powered by the burning desire of pilots to avoid getting real jobs.

You can easily demonstrate the Bernoulli effect by holding a sheet of paper against your lower lip and blowing across the top. That's the demo that always stuck with me.

Blacksheep: remember that, for each of your splendid questions, there are then at least three supplementary questions, all of which are "But why?".

Been there, done that. :ok:

Two angels carry the plane into the air I always thought it was the two Gods in the front seats who did that :p

And don't get kids onto how helicopters fly!



I remember being told that on arrival at Tern Hill in the 70's prospective helicopter pilots were given a copy of a Ladybird book on how helicopters fly. Can any rotary pilots from that era confirm this?

Answering the supplementary questions is the source of all wisdom, Magnus. Especially if you can make the answers plausible. ;)

That'll be where I got it wrong. Yelling "JUST BECAUSE!!!" after the third "but why?" is probably a poor move tactically.

You can easily demonstrate the Bernoulli effect by holding a sheet of paper against your lower lip and blowing across the top. That's the demo that always stuck with me.


@<hidden>

The paper demo and the blowing does not demonstrate Bernoulli's equation. It is a piece of confused thinking propagated by some text books.

It was what I was taught and was the cause of much resentment and embarrassment from me when I said the same to a mathematician brother in law of mine who then proceded to chide me as he explained the whole thing again.

See the excellent explanation and graphics and clips in this link...

http://www.iop.org/EJ/article/0031-9120/38/6/001/pe3_6_001.pdf?request-id=4a408588-062e-4ce5-bbc4-9aa6af630f07


The Bernoulli demonstration

Blowing over a piece of paper does not demonstrate Bernoulli’s equation. While it is true that a curved paper lifts when flow is applied on one side, this is not because air is moving at different speeds on the two sides
MB

Interesting paper; thanks, Michael. I note that the author, while going to great pains to explain what the paper trick doesn't demonstrate, he doesn't explain what it does. :ok:

@<hidden>

You are far more gracious to me than I was to my brother in law! :)

See the section entitled Lift on Aerofoils (after the definition and discussion on streamlines).

Best

MB

Wings are important but don't the engines play a small part...
Not really.

Nervous pax: What happens if the engine stops?
Me: What makes it fly?
Pax (maybe after some prompting): The wings

If the engine stops it doesn't stop flying. If the wings fall off it does. QED.

This thread has answered something about which I've always wondered: now I know that it's angels lifting the aircraft up, this explains the large harp painted on the tail of the 737-800 I normally sit in !

I like the engine/wings logic.

Cue nervous passenger paying rapt attention to the wings. :)

this explains the large harp painted on the tail of the 737-800 I normally sit in


Those planes just fly because gravity wouldn't dare argue with MOL.

Their belligerent supporters now stop fighting and go to Jet Blast instead.


Where they continue to argue about everything from US Politics to how to explain flight to a 4 year old...

I finally figured it all out.

It's a transition thing.

Bernoulli is to flight as floats are to a floatplane taxiing.

Newton is to flight as floats are on the step.

After ground effect is left behind, Newton rules. Fly AoA, not a/s.

(I had a very bad experience in a Swiss restaurant long ago.) Couldn't hurt to bring Archimedes in, could it ?

Interesting that after all these years we still can not actually agree on something so fundamental to flight.

The argument that, because a sail does not have thickness and air appears to pass down both sides at the same speed therefore a wing can not derive lift 'according to Bernoulli" seems to me to be fatally flawed. I can see no reason proposed that proves that sails may not derive their drive from an entirely different phenomena, or one that is somewhat different.

In one so called intelligent yachting magazine I read with amazement that sails derive their power from the vortices that fan out behind them.

I think we have entirely too much time on our hands.

Ah. The reason great minds can disagree is because one infallible rule is as yet undemonstrated.

There is no such 'thing' in Nature as a curved line. Vectors rule, and though they are many, and sequential, the impossibility of a curve is patent to one who sees the Universe as a mathematician, or cosmologist.

A curve requires Time to stop. The Universe is based on bit rash, really.
Due to economy, God does not use curves, they are wasteful of Space.

On the surface of a sphere, one cannot describe a 90 degree angle. It is impossible. Start there. Rivets ?

Next ? Imagination is NOT observation. On this, existence relies. A 'Point' is impossible, it is at best a 'smudge', and that but a figment.

God's Universe is angular. He created us so that he could 'see' things.
God is not a figment of my imagination. I am a figment of His.

Chris

A sail, as you say, is a wing and requires an angle of attack to accelerate the air flow over one side in order to generate downwash (or side wash).

The fact that the sail will also curb/bend in the airstream facilitates this bending to give motive force (reaction) as per Newton's 3rd law.

When a boat is pointing directly into wind (luffing) the airflow is equal on either side of the sail (no angle of attack) and only small unequal random forces are produced and the sail flaps and the boat is not driven forward.

Of course there are more adanced sails that used extremely complex dynamics (ala the Concorde delta wing) to give additional force but before I start going on about this I should admit you are right about getting a life. :)

Life is sequential, a plan is nice. I worked hard at so many things I loved, and now I am allowed to be patient and ponder many things. So many people view life as something that happens to them. I hang out with those whose belief is that life happens for them. Had I been allowed to 'select' my path, I would have been monstrously disappointed.

It would appear when it comes to "How does an airplane fly?" there is an abundance of theory over practice.

As to "How are babies made?" there is little theory but lots of practice! hehehe

What if the kid asks both questions? That could present some interesting "interactive display" possibilities for mom and dad, utilizing the museum's wind tunnel......
while answering those questions. Kinda like killing two birds with one stone.

The majority of the lift is still produced by the deflection of a large amount of air downwards and the application of Newton's 3rd Law (angle of incidence, angle of attack blah, blah, blah).Huge urban legend!

For every action there is an equal and opposite reaction. The air is deflected downwards you say? Correct! But it first has to be deflected upwards, therefore no resultant reaction. All this upwash and downwash is merely the byproduct of the actual reason for lift.

I'm open to theorising on this though - my confidence spawns from the fact this was illustrated to me by a leading Physicist up in Manchester, a reet old brainbox as well!

The majority of the lift is produced (in 99% of wing designs) by the lower than static pressure above the wing (sometimes wrongly referred to as 'suction'). Also, but to a lesser extent, the higher than static pressure below the wing. Even a symmetrical aerofoil, when given an angle of attack, will experience most of its lift from the reduced pressure above the surface as opposed to the diametrically equivilant!

That's how I've always been taught and envisaged it... :confused:

Actually we had many Master Pilots try and teach the principles of flight. Each and everyone failed once they got to 15 deg AOA. None could explain why a Ligntning could climb vertically when the maxium angle to the horizontal, according to the lecture notes, was 15 deg.

@<hidden>

The complication you allude to in the picture of a wing is the effect of "upwash" at the leading edge of the wing.

As the wing moves, air is not only diverted down at the rear of the wing (downwash), but some air is pulled up at the leading edge creating a reverse moment (as per Newton's 3rd Law). This upwash actually contributes to negative lift and more air must be diverted down to compensate for it. Which it is.

given an angle of attack, will experience most of its lift from the reduced pressure above the surface as opposed to the diametrically equivilant!


Air is actually pulled from above (creating a low pressure area) but it is the acceleration of the air above the wing in the downward direction that gives the majority of lift.

Without sufficient air being forced downwards as per F= M * A, most wings would not produce sufficient lift to fly the aircraft.

See also lift/Coanda effect (from the not always so uplifting Wikipedia)

"The vehicle's mass is supported by a dynamic flow of medium beneath its surfaces. This flow is created by the vehicle's thrust forward and the relative 'stability' and the 'incompressibility' of the fluid itself. Since the medium is itself stationary (sic), it's compositon is not related to the medium above the vehicle's surfaces, though it may be identical, and similar in behaviour at less than critical speed."

"In Defense of Newton" the analysis of skiboats and aircraft...Will Fraser


Bernoulli was a plumber, from Switzerland. And Ma never pulls, she pushes.

'Because it does!'

'Now go and bother your mother'

Usual result - ask 3 "experts". get 5 answers.

X is the unkown quantity, and a Spurt is a drip under pressure.

Usual result - ask 3 "experts". get 5 answers.

You are right! This poor 4 year old. :)

Quote Dushan;

As for a simple explanation, the wing has a longer surface on top, than on the bottom. When air travels over those two surfaces at the same speed, it creates a negative pressure on top, sort of a vacuum cleaner effect and keeps the wing in the air.

Air (molecules that are seperated at the leading edge) travels from the leading edge to the trailing edge at the same TIME not SPEED!:eek::ugh:

Love it when OP's are mocked with a normal question, and given an answer that has the very basic laws of aerodynamic flight flawed! :E

Love it when OP's are mocked with a normal question, and given an answer that has the very basic laws of aerodynamic flight flawed! :E

Dave, I explicitly said I wasn't mocking. I was just curious. As for my explanation, you are correct, it was written quickly as a simplistic answer.... yada yada yada...

There's nothing wrong with injecting a little magic into the imaginations of children.

Driving through the Gibbston Valley when the girls were about five, they spotted the frostfighting windmills on several of the vineyards.

"What are those big propellor things for?"

"When there isn't enough rain, they fly the whole vineyard off to somewhere where it's rainier, so the vines can have some water."

The look on their faces was, well, magic.

A notorious post, the origins of which come from John Tarver - Tarver Engineering...

There are still people in this company who think we weigh aircraft to find
out how much they weigh, not to calculate stresses. Of course we need to
know how much the thing weighs. How are we ever going to know how many
Thrust Pixies we need to get the thing off the ground if we don't know the
weight? Or should that be "Lift Demons"? Pixies have largely fallen into
disrepute - something about Bernoulli not being representative in unbounded
conditions and cause and effect being transposed in the Newtonian model.

In fact the use of Lift Demons on civil aircraft programmes is generally not
that good an idea. The Demon binding contract tends to specify payment in
blood or souls. This is readily achievable with aircraft of military
function, but frowned upon in civilian circles as they may attempt to
acquire payment outside of the terms of their binding contract. Lift Demons
are not used on Elf bombers. We don't talk about Lift Pixies too often as it
seems to upset the self-loading cargo.

Pixies require payment in cakes, flowers or nice thoughts. These are readily
sourced either from the in-flight catering, or provided cost-free by the
passengers. Clearly this would not work well within an operational military
environment. Air force cooking is not renowned for the "light and fluffy
texture" that Thrust Pixies demand, the availability of flowers might be
problematic in desert operations, and nice thoughts may also be hard to find
during times of active operations.

There is also a scalability issue. While one rampant Lift Demon would have
few problems supporting a fighter aircraft (particularly if there is an
immediate prospect of blood), it'll struggle to achieve level controlled
flight of a 560tonne Airbus A380. Use of more than one Lift Demon on the
same flight vehicle is contra-indicated (they squabble and eat each other).
Communities of Thrust Pixies can be encouraged to work together on the same
aircraft by the provision of advanced technologies such as Lemon fondant
icing, variegated tulips or in-flight romantic comedies.

Ryanair once requested Leprachauns be installed in place of Lift Pixies, but
leprechauns have a mission statement which indicates their desire for
monetary gain, and their willingness to search all over the world for it.
This makes Lift Leprechauns expensive to keep (gold vs lemon fondant icing),
and makes it difficult to establish a regular route network as the Lift
Leprechauns don't like to continuously visit the same locations. By law,
aircraft also have to have a full complement of In-Flight Gremlins, but
these are generally not a problem unless you feed the Wingtip Vortex Faeries
after midnight.

Superb Bruce! :ok:

Of course South African planes fly due to tokalosh lift!


http://www.africangold.co.za/images/tokaloshexorcistpendantlarge.jpg