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This may seem as an odd question, but I was asked this by a friend, being that I'm the airplane guru, and I couldn't come up with a real answer.

We all know that airplanes are controlled by the four principles of Lift/Weight and Drag/Thrust, right? And lift is created by the wing being shaped to that the air pressure over the wing is less than that under the wing. So how exactly would an airplane keep level flight and/or ascend to a higher altitude while inverted? Wouldn't the shape of the wing make it automatically descend, physically speaking?

Can anyone explain this to someone who isn't a physics major, like me?

"Retreat, hell! We just got here!"-Captain Lloyd Williams, 2nd Marine Division, Belleau Wood, France, WWI

I don't know how the lift would play into it, but I'd assume the principle works similar to the way the space shuttle reaches outer space.

If you have enough thrust you can overcome the "upside-down airfoil supposedly causing negative climb" issue.

Think about it... a bird flying unaided probably can't turn onto its back and climb to higher altitude; it's not designed to. However, if you strap said bird to, say, a model rocket... well, inverted flight can therefore take place... <evil grin>

That's probably a bad example (both physically and visually), but hopefully the shuttle one is better. I think that the answer simply lies in the fact that thrust can overcome the "negative lift" effect you're thinking would be the case.

As for maintaining "level flight" while inverted, it's the same as level flight while right-side up. If an airfoil/wing is designed to generate lift, why doesn't a plane that's flying perfectly horizontal ("level flight") continue to ascend? The 'angle of attack' can't be adjusted, so the plane is probably flying at such an angle of incidence that weight and lift are basically equal.

I'm gonna stop now, since I've probably been wrong throughout my entire post here and I'm gonna be torn apart by some pilots or aviation experts in a few minutes anyway... but that's what seems to make sense in my head.

“Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote.” Benjamin Franklin, 1759

Well, I'm glad at least one other person wonders the same thing I do! I asked that question early in my flying career and got laughed at. And never got an answer, either.

Actually, Kingfrogger, I think you got it pretty close. At least, it makes sense in my mind as well. That's why the fast-movers can fly inverted, but us big fatties can't, since we depend on actual lift more.

See, that's exactly what I said, but he's the physics major and I'm not, so we weren't quite sure. I was actually really surprised that he asked me a question about planes at all, usually he hates when I delve into my favorite subject.

"Retreat, hell! We just got here!"-Captain Lloyd Williams, 2nd Marine Division, Belleau Wood, France, WWI

WOO-HOO!!!

Anyway, I had a bit more to say about it, but I figured I'd stop before giving out more ammunition, in the event that I was in fact wrong.

I'm waiting for someone with a bit more "book smarts" on the subject to drop a line about it, to confirm or correct my theory.

“Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote.” Benjamin Franklin, 1759

THIS SOUNDS LIKE A QUESTION FOR MUDD OR ONE OF OUR OTHER TECHNO WARRIORS,
I JUST KNOW HOW THE FUEL PUMPS WORK

PRESS TO TEST

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Bernoulli's principle is still in effect. The airfoil, though inverted, still has the leading edge tipped slightly up, so the vacuum is still created on the belly-side of the wing, and the air pressure still forces against the top-side of the wing, pushing it up. Just less efficient.

"Now that he had recognized himself as a dead man it became important to stay alive as long as possible."
George Orwell, 1984

Horrido and King Frogger have it Correct.I could right volumes on this. As i have a PHD in this. But the 2 posts above is what answered it.


It is based on the Lift Variable of the wing. Its weight. Thrust and "Angle of attack" of the LV ratio of the airfoil is the variable that over comes the Weight escapeing Gravity.

Sufficient speed and vaccum changes the lift vector by control of the Angle of attack, Angle of incedence, and the amount of thrust required to create the dytnamic pressure to escape Gravity.

This is called thermal Dynamics. It is the meassure of Airflow Force Vs Gravitational Force.

Like Poke stated above, her heavies are useing a singular lift vector to Carry it's weight. For it to do it inverted would require a fully semetrical airfoil like an aerobatic plane and great more amount of thrust.

When you design an aircraft, your focus is in its "Proposed region of flight" To make it happen efficiency is key as the prime vector "Thrust" makes it all possible. The fuel for the thrust once gone. the design needs to have a margin of safe returnability.

Like the a10 that is designed to be mission capable in a low level, high atmosphere pressure and slow speed manueverability. by its very airfoil design it is limited in its top speed. becasue the drag over comes the design.

their is an index, when you design an aircraft. It has a great number of variables each are a force going against each other. this index grows year by year. It is the simple elegance of continued knowledge and technological growth.


"The power to Destroy the planet, is insignifigant to the power of the Air Force----Mudd Vader

Edited by - mrmudd on Dec 29 2003 2:32 PM

Oh, suuure...

Get all "technical" on us.

Oh well... I'm just glad that I was right. I simply put it into layman's terms so us "common folk" could understand it.

“Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote.” Benjamin Franklin, 1759

Mommy my head hurts, does anybody speak english anymore lol.

<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>However, if you strap said bird to, say, a model rocket... well, inverted flight can therefore take place... <evil grin>
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Didn't we try that with a cat in Rocket team?

Overkill??? I'd kill a fly with a howitzer if I had one.

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\"One of you is gonna fall and die, and I'm not cleaning it up\"

I would have jsut said that just as the aerilons(?) can change the direction, you'd just move the stick to change the shape of the wing to produce the proper shape. I bow to Mr Mudd to correct me, I think he's more right, I'm wondering if what I just said adds anything to it.

"Some pup"
Nickname by Fenderstrat72

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Evil is evil, no matter how small.

I see where you're coming from, gifted, but I think I know why that wasn't mentioned.

What I think BR was saying is this:

In using the general principles of flight and an airfoil/wing surface, the bottom of the airfoil is a shorter distance from front to back than the top surface is. Therefore, air travelling over the top of the airfoil moves faster, creating less pressure on top, and the greater pressure on bottom generates what we call "lift". That's a dumbed down explanation, and I'm sure the majority of those that frequent this site already know that.

However, if you <u>invert</u> the airfoil/wing, the shorter surface is now on TOP, and it would seem that the "lift" would now be pushing down, causing the plane to fall.

That's where BR's question came in. If you invert an airfoil, the 'negative lift' would seem to push the wing down, and you wouldn't be able to maintain level inverted flight. You overcome this by changing the angle of incidence, which is essentially governed by adjusting the ailerons, etc., and by increasing thrust to help overcome the lift/gravity struggle.

So yes, in a sense, you're adding onto what we were saying. However, it's more than just "moving the stick".

“Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote.” Benjamin Franklin, 1759

THAT WAS A GREAT QUESTION,

I LEARNED SOMETHING AGAIN ON THE WT!

PRESS TO TEST

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\"Live Free Or Die\"

Always glad to oblige, Santa!

"Retreat, hell! We just got here!"-Captain Lloyd Williams, 2nd Marine Division, Belleau Wood, France, WWI

<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>incidence, <hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

incedence is the relationship of the Main wing to the rear horizontal stabiliser (parallel)

When talking airfoild, the ailerons dependent on the design may creat more Lift pressure, but they also induce drag.

once you input deflection down on the right side it inputs and opposite direction topside of the left wing. This creates "Roll" axis.

By adjusting your Horizontal stabiliser and maintaining a specified amount of "AOA" and thrust you can maintain a level inverted flight. Although it is dependent to the induced drag, excessive AOA and minute thrust will not over come the drag.

Everybody has done this from time to time, Sticking your hand outside the window of a moveing car and flying it as an airfoil in the airflow. Causeing your hand to rise or decend. But if you require a specified ammount of "AOA" at slower speeds to do this, it requires more aoa and has a higher drag index.

This is a good discription of a Flatbottom airfoil.

A fully semetrical airfoil which has an equildistant radius at top mean chord and bottom tapering to the trailing edge, would require signifigant AOA on slower speeds to maintain lift until sufficent speed creates the dynamic pressure to level the flight.

It is the same principle for an arrow, if it doesnt provide sufficient positive AOA in flight then your arrow fals short becasue it fails to maintain thrust and lift, although the dynamic pressure allows it to escape gravity for a short period of time.

The same goes for a rocket.

The a10 has a "Semi Semetrical under camber wing" this design provides great ammount of lift with minimal amount of drag, becasue of the semisemetrical leading edge (reduces Drag) and the rear undercamber Generates lift. Incorporated with the flaps It creats a high amount of lift vaccuum and the tradeoff is a great deal of lag.


here are some sites of intrest

Free airfoil program
http://www.ctaz.com/~kelcomp/airfoils5.htm


Other Free ware NACA airfoil formulas and ratios, programs.
http://www.pdas.com/naca456.htm

"The power to Destroy the planet, is insignifigant to the power of the Air Force----Mudd Vader

So, considering the airfoils and lift coefficients on Indy cars, who wants try and drive one on an inverted track once it's gotten up to speed?...

"Now that he had recognized himself as a dead man it became important to stay alive as long as possible."
George Orwell, 1984

I really like the little birdie with a rocket engine taped to it better. It appeals to the little boy in me.<img src=icon_smile_big.gif border=0 align=middle>

By this time tomorrow I shall have gained either a pearage or Westminster Abbey........Nelson

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No, no, it's not just an 'engine'... you have to strap it to the whole rocket.

The best part is when the parachute deploys and the bird keeps fighting, trying to get out and fly when it's just helplessly floating back down to the ground...

Ahhh...

Eh, not that I've "really" ever tried that...

More than once...

A week...

“Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote.” Benjamin Franklin, 1759

<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
No, no, it's not just an 'engine'... you have to strap it to the whole rocket.

The best part is when the parachute deploys and the bird keeps fighting, trying to get out and fly when it's just helplessly floating back down to the ground...

Ahhh...

Eh, not that I've "really" ever tried that...

More than once...

A week...

“Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote.” Benjamin Franklin, 1759

<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

You seem innocent..this time. Due to a lack of describing said bird.

...Crows. Larger birds require a larger rocket (Or you get a crash & burn). Plus thier call can be particularly amusing.

And they'll more greedily/foolishly walk into a trap, to get some food "carelessly" left laying around.

...Just don't forget protective gloves when fastening them in.

"And I didn't sleep at all last night. But it wasn't insomnia..I was thinking about coffee!"

W.A.B. Moderator. http://www.worldaffairsboard.com/



Edited by - Lunatock on Dec 30 2003 8:47 PM

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According to *AHEM* "popular rumor," pigeons require a dual-stage rocket, with two 'D' engines, to reach the appropriate altitude and velocity.

Also, counter-weights have to be added to the other side of the rocket, so as to prevent the 'lawn dart effect'. Larger fins are needed on the side opposite the pigeon as well.

Of course, this is completely all hearsay... I think...

“Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote.” Benjamin Franklin, 1759

<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
...Crows. Larger birds require a larger rocket (Or you get a crash & burn). Plus thier call can be particularly amusing.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote> Crows requires a pair of two stage D engines, and they have to fire at the same time in both sequences.... its very difficult to keep a crow from cartwhelling.......


not that I've done that either.... since I graduated anyway....




we did launch a 1-32 scale F-4 with two D engines, sadly the wizzo didn't make it through the "ejection" process.

Overkill??? I'd kill a fly with a howitzer if I had one.

_________________
\"One of you is gonna fall and die, and I'm not cleaning it up\"

LOL, this all reminds me of the footage i saw a few years back of pitcher Randy Johnson hitting a large white bird in midair as it flew past homeplate with a 95mph fastball.

NOTHING left but a cloud of feathers.....

It was soooooo kewl

<img src="http://www.worldaffairsboard.com/sigs/snipersig.jpg " border=0>

Poor birds. I knew I was oversimlpifying when I said "Move the stick," I didn't know how else to say it.

"Some pup"
Nickname by Fenderstrat72

_________________
Evil is evil, no matter how small.

<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
LOL, this all reminds me of the footage i saw a few years back of pitcher Randy Johnson hitting a large white bird in midair as it flew past homeplate with a 95mph fastball.

NOTHING left but a cloud of feathers.....

It was soooooo kewl

<img src="http://www.worldaffairsboard.com/sigs/snipersig.jpg " border=0>
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

One of baseballs more memorable moments. Non charging the mound that is. <img src=icon_smile.gif border=0 align=middle>

Not that the one incident involving Nolan Ryan, a grizzled Texan. Having a twenty something Robin Ventura in a headlock, and punching him before they could be seperated isnt as good.

"And I didn't sleep at all last night. But it wasn't insomnia..I was thinking about coffee!"

W.A.B. Moderator. http://www.worldaffairsboard.com/

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