# Tag Info

1

I take it as self-evident that lift can be generated by a wing without any difference whatsoever in the shape of the top or bottom of the wing. After all, balsa wood gliders (or ones that are rubber band powered) fly just fine with completely flat wings. If you look at such a plane, you will see the wing is set at an angle relative to the longitudinal axis ...

4

The reason why the aft ends of airplanes are streamlined is to preserve a smooth flow of air. Just as the fore ends of airplanes are streamlined to smoothly cleave the air, so too the aft ends are streamlined to smoothly reintegrate the flows. Turbulence is bad, regardless of where on the aircraft it occurs. Note that there is more turbulence behind ...

0

Consider helicopters, which are simply aircraft whose wings go in a circle. Then consider those flying platforms consisting of a fan pointed down. The only real difference is whether the wings are big and slow versus small and fast. Lift consists of the momentum (per second) of air directed downward. Momentum is $mv$. That air has kinetic energy ...

0

The lift of a wing is proportional to the square of the air velocity passing over it. If you have a wing it is thus very easy to get a lot of lift just by increasing your speed. In this way, rather than using engine force to lift the aircraft directly, you use the engine force to push you in the direction you want to go as fast as possible. This means you ...

17

Let's look at the relationship between momentum and energy. As you know, for a mass $m$ kinetic energy is $\frac12mv^2$ and momentum is $mv$ - in other words energy is $\frac{p^2}{2m}$ Now to counter the force of gravity we need to transfer momentum to the air: $F\Delta t = \Delta(mv)$ The same momentum can be achieved with a large mass, low velocity as ...

2

I've wondered about this a bit before. I think it's good to hugely simplify things to think about it. Incidentally, I'm absolutely not a source of authority here. I'm just thinking it through from what seems apparent to me. A falling plate You've said specifically that you don't want to think about how wings work, so let's not. Forget about the wing. ...

0

There are planes that tilt the engine down to take off those are called VTOL (vertical Take Off and Landing). These are usually military fighter craft. The reason why they aren't used for general aviation is multifold: First every regulation aircraft must be able to touch down safely after losing an engine, if the engine is what provides the lift then the ...

0

You can also consider how a glider can achieve much greater distances than a rocket, whilst expending no energy at all! Ah, no. One expends energy in the launch phase - an aerotow or winch launch being typical - and gains energy in slope, wave, dynamic or thermal lift and then expends it in overcoming drag. Energy management is one of the most ...

4

Why is an airplane better than a rocket? Because the plane grips the medium. For a rocket to remain at a fixed altitude, it must continually thrust upwards in order to counteract the fall caused by gravity. It does this by pushing down a large amount of air and fuel each second. An airplane can create this same upward force to counteract gravity, but in ...

0

How about this explanation (not that detailed, but simple): The reason is that, if force of lift and force of gravity cancels each other out exactly, then staying airborne requires zero energy. Basically, energy and force are different things. A helium balloon can stay in the air indefinitely, without needing energy to do so, and without the air supplying ...

6

The key point is that wings allow you to "tilt the engine" much more efficiently than actually tilting it. Tilting an engine converts the power only at 1-to-1 ratio, but wings do it better - a Boeing 747 has a lift/drag ratio of 17 at cruise speed, the wing is generating 17 times more lift than the applied engine power.

2

I think You have Your intuitions a bit scrambled. Engine and wings do not have the same function. If You need to make a parallel then wings have the same function of wheels on a car: they provide an efficent way to remain above ground by pushing down on some medium. Wheels push on ground and have no problem keeping your car above it even when the car is ...

4

The important quantity in determining the effectiveness of a wing is its lift to drag ratio. It turns out that the key contributer to a large lift to drag ratio is a large wing span ($b$ in the below equation). As such the large wings on the aircraft can be far more efficient at generating maximum lift with minimal drag that the smaller "wings" of the ...

1

Wings have a much larger surface area than engines, so they are better at preventing a plane's gravitational potential energy from being converted into downward kinetic energy. A plane with gliders instead of wings and engines pointed downward at an angle should be just as energy efficient as a regular plane. The glider might be less practical because the ...

5

It is merely a long comment but hopefully it gets your intuition on the right track. I try to detail the physical part of the reason why having fixed wings is a good thing: You basically ask, why are airplanes more efficient (hence people still produce them despite their less nice maneuverability) well you probably noticed helicopter rotors work pretty ...

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