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Dear friends and followers, welcome back to my channel
today I'll be answering another very important question
Joe, in many videos I can hear the pilots say this while performing a takeoff
"V1"
"Rotate"
"V2"
So what is all these ?
These three speeds play a major part during takeoff roll
so let's look at them in closer detail
Okay first to know this again is a basic introduction about takeoff speeds
The speeds we're talking about today will always follow in that order:
V1
Vr or rotate
and V2
and these speed apply no matter if you sit in a little twin engine Cessna or a Boeing 747
The speed definition is for either plane the same
Okay let's look at V1
Imagine yourself in the cockpit of your plane and apply takeoff thrust to your engine
and as you gently accelerate down the runway
you come to a point where you reach V1
So by the book
V1 is defined as the speed beyond which the takeoff should no longer be aborted
Meaning that in case you experience any trouble with your plane before reaching V1
The classic example would be an engine failure, you would immediately abort your takeoff
and would apply all necessary matters to bring the aircraft to a stop
Although the use of full reverse thrust is not mandatory
I'll come back to that in a second
So in this video here this Airbus A319 applied takeoff thrust
and due to a technical malfunction had to abort to takeoff prior reaching V1
Just listen to the sound of the engines
Now the autobrake system comes active and immediately
applies pressure to the brake cylinders
the ground spoilers are deployed so are the reversers
and the plane and crew come to a safe stop on the runway
The smoke you can see here is coming from the brakes
as they are the primary force slowing down the aircraft
Now let's say there were to be an engine failure
so one of the reverses would be inoperative
and therefore full reverse thrust can't be added to the braking measures as mentioned before
Because V1 needs to be calculated prior every takeoff
taking into acount airplane weight, runway length
wing flaps setting, engine thrust used, runway surface contamination
and environmental factors and even the aircraft brakes
to assure yourself that any given failure prior reaching V1
you'll have enough runway leftover to come to a complete stop
Now if it's just a minor failure you can continue to takeoff
but that's a whole another video about the stop or go decision making
and besides that this is one of the reasons why the captain
keeps his hand on the throttle until the pilot monitoring calls out V1
and then he moves his hands away from the throttle
to not inadvertently abort the takeoff after V1 in case of a failure
So in case you experience any serious malfunction after V1
You'll have to commit yourself to continue the takeoff
otherwise a takeoff abort will lead to a runway overrun
and could severely damage your plane
Next speed to call out is Vr or better known as Rotate
By the book, Vr is defined as
the speed at which the pilot begins to apply control inputs
to cause the aircraft nose to pitch up
after which it will leave the ground
Again Vr is also calculated prior takeoff in accordance
with aircraft weight, environmental facts etc.
And it's the point where the generated lift over the wings
becomes higher than the aircraft weight keeping it on the ground
Easiest way to memorize Vr is the point where the nose will leave the ground
and vortexes are created at the wing tips which rotate behind the aircraft
And the point where the main gear leaves the ground
that's the point where you have reached Vlof, the liftoff speed
Next speed is V2
Now some airlines still have the standard operating procedures to call out V2
Please comment below if you fly with such airline it would be great to know
Okay, again, by the book
V2 is defined as takeoff safety speed, the speed at which the aircraft
may safely climb with one engine inoperative
Okay let's go back to all engines operatives
Now imagine all is normal
you takeoff and someone would measure your height
above ground at the end of the runway like in this picture here
The height measured is the so-called screen height
Now let's go back to V2 and our engine failure situation
In case one engine fails you need to maintain the speed of V2
in order to leave the runway at a screen height of 35 feet or higher
and maintain the climb rate at V2
to be clear of obstacles in the departure sector
and you should be able to maintain that speed and climb rate
until reaching one engine out acceleration altitude
where you then gain speed and retract the slats and flaps
and continue with the emergency procedures
This video here is a great example for V2
As you can see the Boeing 757 hit a bird just after liftoff
and the engine was severely damaged
The pilots maintained V2 and the respective climb rate
retracted the gear and performed all the necessary emergency procedures
flew a traffic pattern and landed the airplane safely
The reasons therefore is when local authorities design departure routes
including obstacle avoidance procedures
They predict that your aircraft is at least capable of maintaining V2 with one engine
and the gear retracted and guarantee obstacle collision protection
But trust me there's a little bit more to it so this was just a basic explanation of V2
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
and make sure to subscribe to my channel
and check out my Instagram account @flywithcaptainjoe
All the best your Captain Joe
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TAKE-OFF速度V1,Vr,V2! 由“機長”Joe解釋 (TAKE-OFF Speeds V1, Vr, V2! Explained by "CAPTAIN" Joe)

452 分類 收藏
Yuxiang Feng 發佈於 2019 年 9 月 10 日
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