They can take off and land without the need for our runway

它們無須跑道就能起飛和降落

They can hover in the air it can maneuver in any direction in a 360 degree space

能懸在空中

This video will unveil the complexity in science behind flying a helicopter

能在空中朝任意方向移動

After going through the physics behind the helicopter flying you will also understand why helicopter pilots are doing an incredibly complex job

本視頻將揭示直升機的複雜性和科學性

Helicopters use the Airfoil principle to generate lift

在瞭解了直升機的物理原理後

When the blades rotate relative to the air the special airfoil shape will generate lift force and make them fly

你會明白直升機駕駛員在做著極其複雜的工作

the blades derive rotation from an engine more specifically a turbo shaft engine

直升機利用旋翼來產生升力

The compressor sucks the air in and pressurizes it fuel is burned in this pressurized and hot air

當旋翼和相對空氣進行運動時

The hot exhaust leaves the combustion chamber passes through a series of turbine stages and make them turn

旋翼的特殊形狀使得空氣對旋翼產生升力，從而讓直升機飛起來

There are two Sets of turbines one turbine set turns the compressor and the other set turns the helicopters rotor shaft

旋翼旋轉的動力來自引擎

Jet Engines of Airplanes are used to generate thrust force

確切來說就是渦輪軸引擎

However the primary function of the helicopters jet engine is to turn the rotor shaft

壓縮機吸入空氣並將其加壓

The most challenging part in helicopter operation is its controls that means how can it fly forward?

燃油在這高溫高壓的空氣劇烈燃燒

how can it fly backward

灼熱的廢氣從燃燒室噴出

sideward

推動一系列渦輪槳葉使之旋轉

Or how can it Take a turn

渦輪有兩組

The answer is quite simple just rotate the helicopter towards the direction you want to move and just fly

一組用來壓縮空氣

When the helicopter is at an angle the Force produced by the blade is not vertical

另一組用來驅動螺旋槳軸

The horizontal component of this Force will make the helicopter move in the desired Direction

飛機的噴氣式引擎通常用來產生推力

the vertical component of the Blade Force will Balance the gravitational force

而在直升機上的噴氣式引擎主要功能是用來扭動螺旋槳

Now the real challenge is how to turn the helicopter in the desired way?

直升機最具有挑戰性的地方，是動力控制

To learn the science behind helicopter turning we need to learn more about the airfoil principle

這意味著，直升機如何向前飛

the lift produced by an airfoil varies with the angle of attack

向後飛

Generally the greater the angle of attack the more the lift

向側面飛

Now think for a moment what happens if the one blade were at one angle of attack and others were at a different angle?

或者轉向

The lift forces acting on the blades will be different in this case

其實答案並不複雜

The variations in the lift forces will definitely result in a torque that can turn the helicopter

就是把旋翼朝著需要前進的方向扭動就好了

You can observe the beautiful blade motion required to achieve this non-uniform Lift Force distribution

當直升機不垂直的時候

It is clear that the blades must keep on changing angle of attack so that at one particular location the angle of attack is

旋翼產生的升力並不垂直

always the same

升力的水平分量推動直升機

Such complex Of the blades is easily achieved by a swash plate mechanism

朝需要的方向前進

Get an exploded view and understand the basic components first

垂直分量則用來平衡重力

The bottom Swash plate does not spin, but it can move and tilt as shown

真正有難度的地方是讓直升機

A top swash plate is fitted on the bottom swash plate Via a bearing

朝需要的方向運動

So the top Swash plate kid inherit all the motion of Bottom Swash plate while at the same time it can rotate independently

要理解這背後的原理，我們首先得弄清楚旋翼原理

Top swash Plate is attached to the rotor Shaft with the help of a driver. So the top swash plate will always move with the blades

升力取決於旋翼與空氣流動方向的夾角

The blades are connected to the top swashplate with the help of control Rods

大體上來說，與流動方向夾角越大，升力越大

The interesting thing about this arrangement is that just by tilting the bottom swashplate

仔細想想

We will be able to achieve the varying Angle Criterion of the blades

如果其中一個旋翼的夾角與其他旋翼不同會怎樣？

That means with this swashplate tilt

每個旋翼產生的升力就會不同

We will always be able to maintain a positive

旋翼之間升力的不同就會對直升機產生一個扭矩

Angle of attack at the rear and a negative angle at the front portion of the rotor disk

由此你可用觀察到旋翼為了產生這種

in short Swashplate tilting backwards produces a torque as shown

不均勻的升力分佈形成的有趣現象

This kind of control is known as cyclic pitch

很顯然，旋翼的夾角必須不斷的變化

now back to the basic helicopter control

以這確定的一個位置產生的夾角是保持不變的

How will this torque affect the helicopters motion?

這麼複雜的旋翼運動其實就是簡單的

The most obvious answer is that the helicopter will turn forward and move as shown

是由一種斜盤機構來產生的

Unfortunately this answer is completely wrong

我們來看個剖析圖來

What happens in reality is the helicopter will turn sideward as shown this is definitely a weird effect

瞭解這個結構的各個元件

By applying torque in One direction to a rotating object the object turns in Different direction

下斜盤不旋轉，但是可以

This effect is known as gyroscopic precession

像這樣上下滑動

Gyroscopic precession is not a new phenomenon of physics if you carefully apply Newton's second law of motion to rotary objects

上斜盤與下斜盤通過一個軸承進行連接

You will be able to predict this phenomenon according to Newton's second law Force is the rate of change of linear momentum?

這樣，上斜盤能夠獨立旋轉的同時

Similarly torque is rate of change of angular Momentum

與下斜盤保持同步運動

Let's consider this rotating blade. It will have an angular momentum as shown now

上斜盤通過一根連杆與旋轉軸相連

assume that the helicopter has tilted as shown due to some torque action if

這樣上斜盤就和旋翼同步運動了

You victoria lee subtract the first angular momentum from the second you can figure out the torque required for this operation it

旋翼通過控制棒與上斜盤相連

Is interesting to note that to turn the helicopter forward the torque applied should be towards sidewards that means to tilt the helicopter?

這個設計有趣的地方在於

Forward the Swash plate should tilt sidewards as shown

調節下斜盤的水平

You can again verify from Newton's second law of motion

我們就能同步控制每根旋翼的夾角大小

that if you keep the front portion at negative angle of attack and the back portion at positive Angle the

這意味著

Helicopter will simply turn sidewards

隨著斜盤的傾斜方向

Gyroscopic precession is a truly intriguing phenomenon, but it conforms perfectly with Newton's second law of motion

我們能夠一直保持旋翼正後方時夾角為正，在前方為負

if you just lift the bottom swashplate without tilting it you can see how the angle of attack of all three blades will vary by

簡單來說，斜盤向後傾斜會產生這樣的扭力

the same amount

這種控制方式叫“週期變矩”

This means that the helicopter lift Force will be the same in all three

我們回到直升機的基本控制

Blades and the helicopter can move up or down without any tilt

這個扭力對直升機的運動產生什麼效果呢？

Such blade control is known as collective pitch

顯而易見的答案是直升機會向前飛

If you have ever seen a helicopter you are all sure to have seen a tail rotor

不過，這個答案是完全錯誤的

every single rotor helicopter needs this tail rotor for effective operation

實際情況是，直升機會這樣朝側方移動

Without the tail rotor the helicopter fuselage would have spun as shown

這看起來很奇怪

This is due to a consequence of Newton's third law of motion

對一個旋轉的物體施加一個力

To Understand it let's focus on the Force transmission part of the rotor

物體卻朝不同的方向運動

We know the rotor gets the force of rotation Via a bevel gear connected to the engine the engine?

這種效應叫做“陀螺進動”

Bevel gear Transmits Force to the rotor bevel gear as shown however according to Newton's third law of motion

陀螺進動在物理學中不是什麼新鮮事

the Rotor bevel gear should Transmit an equal and opposite Force to the engine bevel gear

如果你將牛頓第二定律應用於旋轉的物體

This reaction Force will make the whole helicopter turn opposite to the blade rotation along the helicopter center of gravity

你可以預見到這樣的運動結果

The function of the tail rotor is to prevent such helicopter rotation by producing a force at the tail

根據牛二定律

By properly adjusting pitch angle of the tail rotor

力，是線動量的變化量

Blades the Pilot can easily manipulate the tail rotor Force this way with the help of the tail rotor

同樣的，力矩是角動量的變化量

Yaw motion of the helicopter can also be achieved

回到旋翼的場景中

All the physics behind helicopter operation means that flying a helicopter is a truly challenging task

它具有這樣的角動量

minut variations in Blade Angles make huge variations in Helicopter Behavior

假設直升機要在某些力矩的作用下這樣轉動

Often the pilot has to do two or more operations together to achieve the desired motion

你得需要施加這樣的力矩來讓角動量從第一位置移到第二位置

moreover the helicopter does not respond instantaneously to your inputs so the pilot should possess a good sense of balance and

有趣的是，要讓直升機朝前方轉動

coordination to navigate the Helicopter properly

扭矩必須是朝側向的

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這意味著，直升機要朝前方前進

Thank you

必須把斜盤朝側向扭動