Why do plains, shuttles, & man made things that fly have 3 wings?

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why do plains, shuttles, & man made things that fly have 3 wings? My parents told me it was so the craft doesn't go into a constant spin. But like i wanta know more like in layman's turms and in picktures and stuff. Can anyone help me please?
 
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davo said:
why do plains, shuttles, & man made things that fly have 3 wings? My parents told me it was so the craft doesn't go into a constant spin. But like i wanta know more like in layman's turms and in picktures and stuff. Can anyone help me please?
Well, the B-2 is one giant flying wing.

The three wings, I'm guessing are the pair of wings proper, which protrude horizontally or at a slight upward angle from the fuselage and provide the lift, the elevators, which are small wings in the rear of the aircraft which provide for control of pitch, and the tail and rudder which provide for turning and yaw control.

http://www.grc.nasa.gov/WWW/K-12/airplane/airplane.html
 
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Astronuc said:
The Space Suttle has a single pair of wings and tail. It mainly glides, or 'falls' to the landing site.
Not necessarily true. The shuttle is a lifting body. The entire fuselage acts as a wing.

I can only assume that the OP is referring to a wing, a vertical and horizontal stabilizer. It's tough to say though. The last time I saw anything with three wings was WW1.
 
FredGarvin said:
Not necessarily true. The shuttle is a lifting body. The entire fuselage acts as a wing.
True the Shuttle's fuselage and wing undersurfaces are continuous. I only indicated that it had continuous wings as opposed to wings and elevators (in the rear). I think the Shuttle is mainly a glider. It is transported piggy-back on a special 747, or it lifts vertically on thrust.

In the atmosphere, I believe it simply glides since there is no SSME thrust (MESO with ejection of external tank), and I don't believe the orbital RCS thrusters are used during descent in atmosphere. They have one shot at landing - there is no second chance.

I can only assume that the OP is referring to a wing, a vertical and horizontal stabilizer.
That's what I assumed too.
 
FredGarvin said:
The last time I saw anything with three wings was WW1.

Cool; I'd forgotten how old you are.
If memory serves, the shuttle has about the same glide ratio as a brick.
 
Astronuc said:
Well, the B-2 is one giant flying wing.

The three wings, I'm guessing are the pair of wings proper, which protrude horizontally or at a slight upward angle from the fuselage and provide the lift, the elevators, which are small wings in the rear of the aircraft which provide for control of pitch, and the tail and rudder which provide for turning and yaw control.

http://www.grc.nasa.gov/WWW/K-12/airplane/airplane.html

thank you that does help a lot but also from what I've reserched it can be a called an empennage. Does anyone know why there alwase in the rear of the craft?
 
davo said:
why do plains, shuttles, & man made things that fly have 3 wings? My parents told me it was so the craft doesn't go into a constant spin. But like i wanta know more like in layman's turms and in picktures and stuff. Can anyone help me please?

Don't think of it as 3 wings but rather as two plane surfaces (horizontal wings and vertical stabilizer).

Then think of what you want an aircraft to do and what you want it not to do.
 
jambaugh said:
Don't think of it as 3 wings but rather as two plane surfaces (horizontal wings and vertical stabilizer).

Then think of what you want an aircraft to do and what you want it not to do.

thank you, also from what I've reserched it can be a called an empennage. Does anyone know why there alwase in the rear of the craft?
 
http://en.wikipedia.org/wiki/Empennage
Empennage [ émpənij ] is an aviation term used to describe the tail portion of an aircraft. ("Empennage", "tail", and "tail assembly" may be interchangeably used.) The empennage gives stability to the aircraft and controls the flight dynamics: pitch and yaw. In simple terms the empennage may be compared to the feathers of an arrow, colloquially; "Tail Feathers"

Structurally, the empennage consists of the entire tail assembly, including the fin, tailplane and the part of the fuselage to which these are attached. On an airliner this would be everything behind the rear pressure bulkhead.

The front, usually fixed section of the tailplane is called the horizontal stabilizer and is used to balance and share lifting loads of the mainplane dependent on centre of gravity considerations by limiting oscillations in pitch. The rear section is called the elevator and is usually hinged to the horizontal stabilizer. The elevator is a movable airfoil that controls changes in pitch, the up-and-down motion of the aircraft's nose.

Well the tail is always at the rear, where is provides the maximum stability. The vertical stabilizer, or tail, controls the sideways motion or 'yaw'. The elevators, horizontal stabilizers, controls the pitch of the aircraft (nose up or down). The elevators provide maximum moment located as from the center of gravity of the aircaft. Placing them at the rear also provides more stability.
 
davo said:
thank you, also from what I've reserched it can be a called an empennage. Does anyone know why there alwase in the rear of the craft?
It isn't always the case, just most of the time. But for a demonstration of why, try throwing a dart backwards...
 
davo said:
thank you, also from what I've reserched it can be a called an empennage. Does anyone know why there alwase in the rear of the craft?

A cannard design has control at, or near the nose of the craft.
 
davo said:
thank you, also from what I've reserched it can be a called an empennage. Does anyone know why there alwase in the rear of the craft?
Their location is always going to be a function of the forces created during flight. They are put where they need to be most effective. The original Wright Flyer used a canard system with the main control surfaces in front of the aircraft.
 
FredGarvin said:
Their location is always going to be a function of the forces created during flight. They are put where they need to be most effective. The original Wright Flyer used a canard system with the main control surfaces in front of the aircraft.

It just occurred to me that the Wright Flyer's canard system probably resulted from their experience with stability of bicycles and other wheeled vehicles with front steering. A bad analogy as it turns out.

The main virtue of the canard system, if I am not mistaken, is that in a stall the nose looses lift first and drops allowing the craft to gain speed before the stall occurs in the main lift wings.

I suppose this came in quite handy in those early flights with a too heavy, underpowered craft.
 
now if the empennage was moved to the front and the back wings are still in the back couldn't the craft have a better turning ratio? Also wouldn't the lift be not only in the back of the craft but in the front as well?
 
davo said:
now if the empennage was moved to the front and the back wings are still in the back couldn't the craft have a better turning ratio?
There is always an uneasy tog-of-war between stability and manueverability.

You want an excellent turning radius, put the tail on the nose. It'll turn on a dime. Well, a good fraction of it will, anyway...
 
It occurs to me that control surfaces that trail the bulk of the plane are relatively well-protected from damage. After to the pilot, they're the next most important thing to keep the plane from making unscheduled landfall.
 
I think the general reason why it doesn't work well with the empennage at the front is that it is inherently unstable - it is a positive feedback loop. Controls are designed to rotate a craft out of true. As this happens surfaces at the front become more effective as they bite into the wind more, causing the rotation to be amplified.

Surfaces at the back, on the other hand, are in a negative feedback loop; they become less effective as the plane is rotated out of true. i.e. the craft tends to self-correct, wanting to return to true. This is the way to keep a craft stable.

Easy to experiment with. Stick your hand out the window next time you're passenging in a car.
 
DaveC426913 said:
I think the general reason why it doesn't work well with the empennage at the front is that it is inherently unstable - it is a positive feedback loop. Controls are designed to rotate a craft out of true. As this happens surfaces at the front become more effective as they bite into the wind more, causing the rotation to be amplified.

Surfaces at the back, on the other hand, are in a negative feedback loop; they become less effective as the plane is rotated out of true. i.e. the craft tends to self-correct, wanting to return to true. This is the way to keep a craft stable.

Easy to experiment with. Stick your hand out the window next time you're passenging in a car.
ok thank you.
 
just one question now that I took a better look at it. can i have the empennage in the rear but extend to the front?
 
davo said:
just one question now that I took a better look at it. can i have the empennage in the rear but extend to the front?
What?

Do you mean like http://www.fas.org/man/dod-101/sys/ac/x-29-EC87-0182.jpg"?
 
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