So if an airplane tries to take off from a large conveyor belt ....
- Thread starter Dogmeat
- Start date
Wait, is the conveyor belt moving or is the plane?
If the conveyor belt is able to move 200 miles per hour and the cessna that you are in is only able to reach a top take off speed of 199 and both are travelling in opposite directions will you take off then?
If you were walking on the ground next to the conveyor belt that was travelling the opposite direction to the plane and the plane was accelerating at the same speed that the conveyor was moving would you be able to pull the plane backwards if you had a rope tied to the tail?
Hey, what if you turned the plane around would you be able to take off in a shorter distance?
To answere these questions with a prop plane vs a jet is there a difference?
if so, would a rocket on a conveyor not move either if the conveyor was moving ar the same rate of speed and acceloration?
Could you hammer a nail into a board if you were falling with all three objects?
If the conveyor belt is able to move 200 miles per hour and the cessna that you are in is only able to reach a top take off speed of 199 and both are travelling in opposite directions will you take off then?
If you were walking on the ground next to the conveyor belt that was travelling the opposite direction to the plane and the plane was accelerating at the same speed that the conveyor was moving would you be able to pull the plane backwards if you had a rope tied to the tail?
Hey, what if you turned the plane around would you be able to take off in a shorter distance?
To answere these questions with a prop plane vs a jet is there a difference?
if so, would a rocket on a conveyor not move either if the conveyor was moving ar the same rate of speed and acceloration?
Could you hammer a nail into a board if you were falling with all three objects?
as i recall, the earth itself is a huge conveyor... travelling at just over 1000mph, yet a 199mph cessna can still take off... DUH!!!!!
is the airplane bombardier powered? Then no, it will probably crash on takeoff
R
RMK7SledHead
Well-known member
OK so that being the case, Why do we move when we run? Yes technically we are moving when we are standing still due to the earths rotation and if it stopped abruptly we would all be thrown off this giant conveyor. you are right with your analogy, kind of (there is no motor turning this giant conveyor we are on) but in these questions we are adding a second conveyor.
Let's for sake of arguement remove the conveyor all together and put one plane inside another larger plane. A plane so large that the smaller one could fly around inside it. If the larger plane was travelling at the speed of sound and the plane inside took off flying 1/2 that speed in the opposite direction and out of the back of the bigger plane. Would it stop if it was flying at half the speed of sound?
AAAAH...sorry....that happened so many times around here, it's too easy to forget....that's probably why these new XP's are supposed to be so 'light'...they can't handle hard landings...
Ya, we got a whole load of fuggin' rocket scientists on here.
so what if you get a really little plane....say a piper pacer capable of 125MPH (a real rocketship, I know) and the conveyor is moving at 250MPH against the plane before you even get the engine (singular) to fire.
Now there's two options. Either you're holding still because the wheels can spin free...or there's friction in the wheels (it is a tail dragger after all) and you're now moving backwards at 250MPH.
We'll assume friction does exist in this theoretical problem.
So you're in this little fabric plane rolling backwards twice as fast as you've ever gone forwards in it, you've soiled your favorite flying pants and you can't get the tower to acknowledge your mayday. Turns out the conveyor doesn't have flight traffic control. crap. That tiny little 125horse engine slowly sputters to life and you finally have something nice to say about your smart mouthed A&P guy.
Now let's remember that this itty bitty engine can only muster 125mph, but the plane weighs less than a wet apex so it takes off at 43mph.
So you're hurtling backwards towards god knows what at 250MPH...your prop starts spinning fast enough to propel you forwards at 125MPH on unmoving ground....you need 43MPH (air speed) to get lift....what happens?
(I'm no rocket scientist so please don't give me multiple choice)
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so what if you get a really little plane....say a piper pacer capable of 125MPH (a real rocketship, I know) and the conveyor is moving at 250MPH against the plane before you even get the engine (singular) to fire.
Now there's two options. Either you're holding still because the wheels can spin free...or there's friction in the wheels (it is a tail dragger after all) and you're now moving backwards at 250MPH.
We'll assume friction does exist in this theoretical problem.
So you're in this little fabric plane rolling backwards twice as fast as you've ever gone forwards in it, you've soiled your favorite flying pants and you can't get the tower to acknowledge your mayday. Turns out the conveyor doesn't have flight traffic control. crap. That tiny little 125horse engine slowly sputters to life and you finally have something nice to say about your smart mouthed A&P guy.
Now let's remember that this itty bitty engine can only muster 125mph, but the plane weighs less than a wet apex so it takes off at 43mph.
So you're hurtling backwards towards god knows what at 250MPH...your prop starts spinning fast enough to propel you forwards at 125MPH on unmoving ground....you need 43MPH (air speed) to get lift....what happens?
(I'm no rocket scientist so please don't give me multiple choice)
1st, unless this is in a vacuum, the plane would be ripped to shreds as it will
not withstand the 250 mph tail wind created by the rearward movement.
But, ignoring that fact, the prop would eventually overcome the rearward
momentum once again making the conveyor a moot point.
Isn't lift more or less a product of speed and wing design? If it's all about thrust than why bother wasting all that precious aluminium on wings in the first place?
Actually, my vote is for spontaneous combustion too.
Actually, my vote is for spontaneous combustion too.
Does it fly, stand still, or get run off the back of the conveyor belt?
.. More info is needed... Dog doesn't say anything about the belt EVEN being turned on, much less running in a direction opposing lift.. AND,, is the belt secured to the ground? does the intake act like a huge vacum & suck the belt into the turbines?
J
Jaynelson
Well-known member
It will take off the same as if it was not on a conveyor belt...the wheels will just be spinning faster. Had this arguement many times and the answer is evetually always the same...althought it takes forever to get there for some.
The wheelspeed is completely irrelevant because a plane isn't powered by its wheels. The wheels are free spinning, and the force is applied via the engines to the air.
Hold a skateboard on a treadmill with your hand and turn it on....as fast as that treadmill turns, it's still very easy to push the board forward on the treadmill with your hand. Same thing.
The wheelspeed is completely irrelevant because a plane isn't powered by its wheels. The wheels are free spinning, and the force is applied via the engines to the air.
Hold a skateboard on a treadmill with your hand and turn it on....as fast as that treadmill turns, it's still very easy to push the board forward on the treadmill with your hand. Same thing.
I thought Physics class gave me a headache
so what if you get a really little plane....say a piper pacer capable of 125MPH (a real rocketship, I know) and the conveyor is moving at 250MPH against the plane before you even get the engine (singular) to fire.
Now there's two options. Either you're holding still because the wheels can spin free...or there's friction in the wheels (it is a tail dragger after all) and you're now moving backwards at 250MPH.
We'll assume friction does exist in this theoretical problem.
So you're in this little fabric plane rolling backwards twice as fast as you've ever gone forwards in it, you've soiled your favorite flying pants and you can't get the tower to acknowledge your mayday. Turns out the conveyor doesn't have flight traffic control. crap. That tiny little 125horse engine slowly sputters to life and you finally have something nice to say about your smart mouthed A&P guy.
Now let's remember that this itty bitty engine can only muster 125mph, but the plane weighs less than a wet apex so it takes off at 43mph.
So you're hurtling backwards towards god knows what at 250MPH...your prop starts spinning fast enough to propel you forwards at 125MPH on unmoving ground....you need 43MPH (air speed) to get lift....what happens?
(I'm no rocket scientist so please don't give me multiple choice)
How fast can the plane go with a 250 MPH tailwind? Me thinks it would be roughly 375 MPH (125 MPH past the point where there is no wind.)
so what if you get a really little plane....say a piper pacer capable of 125MPH (a real rocketship, I know) and the conveyor is moving at 250MPH against the plane before you even get the engine (singular) to fire.
Now there's two options. Either you're holding still because the wheels can spin free...or there's friction in the wheels (it is a tail dragger after all) and you're now moving backwards at 250MPH.
We'll assume friction does exist in this theoretical problem.
So you're in this little fabric plane rolling backwards twice as fast as you've ever gone forwards in it, you've soiled your favorite flying pants and you can't get the tower to acknowledge your mayday. Turns out the conveyor doesn't have flight traffic control. crap. That tiny little 125horse engine slowly sputters to life and you finally have something nice to say about your smart mouthed A&P guy.
Now let's remember that this itty bitty engine can only muster 125mph, but the plane weighs less than a wet apex so it takes off at 43mph.
So you're hurtling backwards towards god knows what at 250MPH...your prop starts spinning fast enough to propel you forwards at 125MPH on unmoving ground....you need 43MPH (air speed) to get lift....what happens?
(I'm no rocket scientist so please don't give me multiple choice)
I'll see if I can give a logical response to this one, but first you have to make a couple of assumptions.
1)the conveyor belt does not create a significant disturbance to the air surrounding the airplane;
2) the wheels, tires, and bearings can withstand speeds described below;
3) your initial velocity in relation to the surrounding air is 0 MPH.
When the conveyor starts, it cause the wheels to freewheel backwards at 250 MPH so long as the pilot is not on the brakes. The small friction in the wheel bearings will cause the airplane to accelerate backward. However, since this friction is small, the backward acceleration of the airplane will also be small. As long as the pilot can get the engines started quickly, the backward velocity of the airplane will not be very high since the acceleration is small.
When the pilot ramps up the engines, the forward force of the thrust will quickly overcome the backward force of the wheel bearing friction, resulting in a forward acceleration. The airplane will transition from moving backward to moving forward. It will continue to accelerate until it takes off.
I will simplify this for everyone.......If any plane is moving backwards on a giant conveyor at any speed it will have to go forward at whatever over that speed it needs to take off.
So we will use simple numbers to explain......if a plane is travelling backwards on a conveyor at 100 mph and needs to be going 100 mph to take off it will have to accelorate to 200 mph before it will lift off.
There is your answer. Case closed
So we will use simple numbers to explain......if a plane is travelling backwards on a conveyor at 100 mph and needs to be going 100 mph to take off it will have to accelorate to 200 mph before it will lift off.
There is your answer. Case closed
I can also tell you that if the conveyor accelorates at the same speed as the plane does the plane will not move and therefore not generate the required airspeed to lift off. I have done this at Chuck Norrises airport.
