today I'll be answering another very important question

今天我要回答另一個非常重要的問題

Joe, in many videos I can hear the pilots say this while performing a takeoff

Joe 我在很多影片聽到飛行員在起飛時說了這些

"V1"

V1

"Rotate"

Rotate

"V2"

V2

So what is all these ?

所以這些是什麼意思?

These three speeds play a major part during takeoff roll

這三個速度在起飛時扮演很重要的角色

so let's look at them in closer detail

所以讓我們進一步來了解

Okay first to know this again is a basic introduction about takeoff speeds

我們一開始要知道這些是起飛速度最基礎的指示

The speeds we're talking about today will always follow in that order:

我們今天談論的都會以下列形式出現

V1

V1

Vr or rotate

Vr or rotate

and V2

and V2

and these speed apply no matter if you sit in a little twin engine Cessna or a Boeing 747

不管你坐在雙引擎的西斯納或波音747，這些速度代號都能使用

The speed definition is for either plane the same

這些速度的定義不管在甚麼飛機上都是一樣的

Okay let's look at V1

我們先來看V1

Imagine yourself in the cockpit of your plane and apply takeoff thrust to your engine

想像你坐在駕駛艙中，推力設定至起飛動力

and as you gently accelerate down the runway

當你慢慢在跑道上加速

you come to a point where you reach V1

你的速度到了V1

So by the book

根據書本

V1 is defined as the speed beyond which the takeoff should no longer be aborted

V1的定義是:在此速度上不能中止起飛

Meaning that in case you experience any trouble with your plane before reaching V1

代表如果你在到達V1前遇到任何問題

The classic example would be an engine failure, you would immediately abort your takeoff

發動機失效是一個經典的例子，你會馬上中止起飛

and would apply all necessary matters to bring the aircraft to a stop

並用盡全力讓飛機停下來

Although the use of full reverse thrust is not mandatory

儘管發動機反推並不是必要的

I'll come back to that in a second

我等等會再回來講這個

So in this video here this Airbus A319 applied takeoff thrust

在這個影片裡面一架A319將推力設置在起飛動力

and due to a technical malfunction had to abort to takeoff prior reaching V1

因為技術性問題需要在到達V1前需要中止起飛

Just listen to the sound of the engines

仔細聽發動機的聲音

Now the autobrake system comes active and immediately

現在自動煞車系統自動啟動

applies pressure to the brake cylinders

並立刻施加壓力至煞車碟盤

the ground spoilers are deployed so are the reversers

擾流板已經打開且反推裝置已啟動

and the plane and crew come to a safe stop on the runway

飛機和組員在跑道上安全的停下

The smoke you can see here is coming from the brakes

你在這邊看到的煙是來自煞車

as they are the primary force slowing down the aircraft

因為煞車是讓飛機停下的主力

Now let's say there were to be an engine failure

讓我們假設他們是遇到發動機失效

so one of the reverses would be inoperative

所以有其中一個反推裝置無法正常運作

and therefore full reverse thrust can't be added to the braking measures as mentioned before

所以全力反推並不能增加煞車的量值

Because V1 needs to be calculated prior every takeoff

因為V1必須在每次起飛前計算

taking into acount airplane weight, runway length

將飛機重量、跑道長度

wing flaps setting, engine thrust used, runway surface contamination

襟翼設定、引擎推力、跑道狀態

and environmental factors and even the aircraft brakes

還有環境因子甚至煞車納入考量

to assure yourself that any given failure prior reaching V1

來保證若在V1前遇到問題

you'll have enough runway leftover to come to a complete stop

你有足夠的跑道餘度來讓飛機完全靜止

Now if it's just a minor failure you can continue to takeoff

如果不是緊急的問題你仍然可以繼續起飛

but that's a whole another video about the stop or go decision making

但那需要另一個完整的影片來說明怎麼做決定

and besides that this is one of the reasons why the captain

除此之外這也是為什麼機長

keeps his hand on the throttle until the pilot monitoring calls out V1

會一直將手放在節流閥上直到PM說V1

and then he moves his hands away from the throttle

他才會將他的手離開節流閥

to not inadvertently abort the takeoff after V1 in case of a failure

避免不小心在V1後遇到問題時中止起飛

So in case you experience any serious malfunction after V1

所以假設你在V1後遇到很嚴重的故障

You'll have to commit yourself to continue the takeoff

你必須強迫自己繼續完成起飛

otherwise a takeoff abort will lead to a runway overrun

否則你在中止起飛時可能會衝出跑道

and could severely damage your plane

並嚴重毀損你的飛機

Next speed to call out is Vr or better known as Rotate

下一個喊出的速度是Vr或是較常聽見的Rotate

By the book, Vr is defined as

根據書本，Vr的定義為

the speed at which the pilot begins to apply control inputs

飛行員開始輸入控制量的速度

to cause the aircraft nose to pitch up

來讓飛機抬頭

after which it will leave the ground

在此之後將會離開地面

Again Vr is also calculated prior takeoff in accordance

再次說明，Vr 也是在起飛前就計算好的

with aircraft weight, environmental facts etc.

依據飛機重量，環境因子...等

And it's the point where the generated lift over the wings

那是機翼開始產生升力的點

becomes higher than the aircraft weight keeping it on the ground

並大於讓飛機留在地上的重量

Easiest way to memorize Vr is the point where the nose will leave the ground

簡單來說，Vr是機鼻離開地面的時刻

and vortexes are created at the wing tips which rotate behind the aircraft

並在翼尖產生在主翼後旋轉渦流

And the point where the main gear leaves the ground

當主輪離開地表的時候

that's the point where you have reached Vlof, the liftoff speed

那就是我們說的Vlof或liftoff speed

Next speed is V2

下一個速度是V2

Now some airlines still have the standard operating procedures to call out V2

現在有些航空公司仍保有喊出V2的SOP

Please comment below if you fly with such airline it would be great to know

如果你在這樣的公司工作請在下面留言，我很想知道

Okay, again, by the book

又一次，根據書本

V2 is defined as takeoff safety speed, the speed at which the aircraft

V2定義為安全起飛速度

may safely climb with one engine inoperative

可以在一個發動機失效後安全的爬升

Okay let's go back to all engines operatives

我們回到所有發動機都正常運作

Now imagine all is normal

想像所以情況都很正常

you takeoff and someone would measure your height

你起飛然後有個人測量你的高度

above ground at the end of the runway like in this picture here

在跑道尾端的距地高度，如圖所示

The height measured is the so-called screen height

這個高度稱為 screen height

Now let's go back to V2 and our engine failure situation

現在回到V2和發動機失效的狀況

In case one engine fails you need to maintain the speed of V2

假設一個發動機失效你需要保持在V2的速度

in order to leave the runway at a screen height of 35 feet or higher

為了在離開跑道時達到screen height 35呎或更高

and maintain the climb rate at V2

並保持在V2時的爬升率

to be clear of obstacles in the departure sector

來避免在離場路徑上的障礙物

and you should be able to maintain that speed and climb rate

而且你應能夠保持那個速度和爬升率

until reaching one engine out acceleration altitude

直到到達單發動機失效的加速高度

where you then gain speed and retract the slats and flaps

這時你才開始加速並收回縫翼和襟翼

and continue with the emergency procedures

並繼續進行你的警急狀況程序

This video here is a great example for V2

這是一個很棒的V2例子

As you can see the Boeing 757 hit a bird just after liftoff

你可以看到一架波音757在剛起飛時遇上鳥擊

and the engine was severely damaged

發動機嚴重受損

The pilots maintained V2 and the respective climb rate

飛行員保持V2和相對應的爬升率

retracted the gear and performed all the necessary emergency procedures

收回起落架並執行所有必要的警急程序

flew a traffic pattern and landed the airplane safely

飛了一個本場航線並安全的降落

The reasons therefore is when local authorities design departure routes

這樣做的原因是當局在設計離場航線時

including obstacle avoidance procedures

包含閃避障礙物的程序

They predict that your aircraft is at least capable of maintaining V2 with one engine

他們假設你的飛機至少能單發動機的狀態下維持在V2。

and the gear retracted and guarantee obstacle collision protection

起落架收起且保證不會撞到障礙物

But trust me there's a little bit more to it so this was just a basic explanation of V2

旦相信我這裡面還有更多，這只是對V2的基本解釋

Okay I hope you enjoyed this short little video about the takeoff speeds

next week's video will be all you need to know about ram air turbines

so stay tuned for that and tomorrow I will be uploading

my 100,000 followers thank you video

so please make sure to check that out

because I need your feedback on that video you'll see why

Thanks for your time, see you next Thursday

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All the best your Captain Joe