Let's say you had a giant treadmill with an airplane on it

[PCL_128]

Where's mythbusters when you need 'em?

They were already asked to look at this myth, and they refused because they said any moron could understand that the plane would takeoff without a demonstration.

 

[FR8mastr]

another way to look at is an airboat in a river. The thrust of the airboat is from an airplane propeller.

Aim the airboat up river and give her all she's got. If the river keeps accelerating downstream as you speed up going upstream. Will you move?

If the top end of the airboat is 100kts, and the river is flowing at 100 kts the other way, will you have moved past the dock you just left on the shoreline?

 

[fartknocker]

They were already asked to look at this myth, and they refused because they said any moron could understand that the plane would takeoff without a demonstration.

Instead of calling others names, you are now resorting to self incrimination??

 

[Oakum_Boy]

I am jumping in here a little late, but the folks saying the airplane will fly, just exactly what is the takeoff path going to look like? Straight up like a UFO, or regular-like.

 

[GuppyWN]

I can't tell who's funnier. The guys lobbing in the sarcasm or the people who are legitimately arguing the point of this sillyness.

Gup

 

[Stifler's Mom]

More importantly, can you log treadmill time as PIC?

PS I'm bringing a model airplane to the gym tomorrow. I need to know.

 

[mrnolmts]

Why on earth are we discussing this one again??? And FS, I thought you were smarter than this
You guys are thinking as if the engine produces forward motion via the wheels. The wheels are only there to make it easier for the engine and propeller to pull the airplane on the ground, guys... Well, and for somewhat smoother landings, I guess...
Look at it this way (using a small SE prop for ease of understanding):

You are standing in front of the airplane, holding it by the propeller blades. YES, the engine is off!!! Wheels are on a threadmill, brakes released. And yes, YOU are standing on solid ground.
The threadmill starts up, slowly at first, then faster and faster. Initially, you'll feel a tug, as the wheels start spinning, but you'll find that it's actually not that hard keeping the airplane still as the wheels go faster and faster. Yes, I know, eventually you'll get to the point that you can't hold it any longer, but that is at a much higher wheelspeed than you apparently think.
Now realize how much more pulling power that engine and propeller has. It'll easily overcome the small amount of friction the threadmill is exerting on the wheels. Thus, the airplane will move forward on the threadmill, and it will become airborne at normal indicated airspeed. TIRE speed will be way higher than normal, but assuming the tires will withstand those speeds, the airplane will be airborne LONG before the friction from the threadmill is at the point of countering thrust.

 

[G2T]

dumbass

Thanks for that very informative and mature response to my post. That makes me think very highly of yourself and your opinion.

 

[Flyer1015]

Why do airplanes have wheels Einstein?

So mx doesn't have to re-skin the belly every time the ham-fisted sky monkeys land.

Are those wheels powered?

(I won't answer that-you have to figure it out)

What does the powerplant of an aircraft push against?

(I don't give a flying frack at a rolling douhnut if it burns gas or kerosene-it doesn't matter)

Have you ever seen a floatplane take off going upstream on a river? Yeah, they get into the air just fine. Takes a little longer but they do just fine.

Now I want you to go to the gym and do an experiment. Not really, since you are obviously not an expert you shouldn't do this. Not at home or in someone else's gym. In fact, the illustration that follows is just that...an illustration. Do not do it. IMHO You shouldn't even be out in public unsupervised!

Get on your tread mill and crank the speed up just as fast as you can run. Then grab ahold on the pedistal that has the odometer and heart rate thingy on it. Run like a hamster on a wheel untill you are starting to get your runner's high...
then with both arms pull on the pedistal as suddenly and violently as you can!

did you move???

Do you have any contusions or lacerations? Bruises? Well, have a shot of tequilla and consider yourself lucky to be alive!

(surely no-one here is dense enough to do this!)

Again, do not try this at home...you are not an expert and you don't know what you are doing...clearly and above all else you know not what you are doing.

I'm surprised some of you can get to the airport alive...let alone find your way back to your computers! Did you all go to embry riddle or Purdue?

hehehehehe...

belchfire, don't bother. I already posted what is the 'correct' answer to this whole thing.


It's the ask the pilot column on salon.com , just backtrack and find the link I posted.

 

[belchfire]

I can't tell who's funnier. The guys lobbing in the sarcasm or the people who are legitimately arguing the point of this sillyness.

Gup

How about a helicopter. Some of them have wheels...

hehehehe...

 

[Gnarloooo]

You fat lards need to get away from the computer and get on a treadmill yourselves.

 

[belchfire]

belchfire, don't bother. I already posted what is the 'correct' answer to this whole thing.


It's the ask the pilot column on salon.com , just backtrack and find the link I posted.

Yeah...sorry...I didn't get that far before I responded. The whole setup is kind of goofy but airplanes are designed to overcome rolling friction and aerodynamic drag in order to take off. Once movement starts -let me be very clear about this - once airspeed is indicated rolling friction rapidly becomes the lesser of the forces resisting acceleration as aerodynamic drag is increasing as the square of airspeed far beyond the point where rolling drag tops out.

Right out of brake release a typical heavy jet is accelerating pretty slowly but by the time rotation speed is reached the may be accelerating at a rate of 3 knots per second.

The presumption by the naysayers is that rolling friction can keep the aircraft from moving. The fact is that as liftoff airspeed is approached rolling friction is a small fraction of the forces acting on the aircraft. In order to reach takeoff speeds you have to be able to overcome the resistance of the wheels.

 

[McNugget]

drinking and on the computer.

how cool

Hahaha

And you wonder why your woman calls this place the "Gay Hangar News"?

 

[belchfire]

You fat lards need to get away from the computer and get on a treadmill yourselves.

That's "fat laird" you peasant...back to work or I'll have you broken under the wheel!

 

[regionaltard]

belchfire, don't bother. I already posted what is the 'correct' answer to this whole thing.


It's the ask the pilot column on salon.com , just backtrack and find the link I posted.

Oh, it's on the Internet. Must be right then.

 

[405]

You guys should get some little balsa rubber band propelled airplanes and try these experiments at a major airport near you with those human conveyor belts. Maybe they could crank up the speed to about 30 MPH for you. Martha and Elmer trying to get to CID for $69 round-trip might go flying off the end of the thing and slam into the floor but you could at least possibly prove your point.

Just a suggestion. Good luck.

 

[ImbracableCrunk]

I thought I would dust off this old gem to kill the PIC thread.

Let's say you had a giant treadmill with an airplane on it.

As you add power and begin to move for the takoff roll, the treadmill speeds up and keeps the plane in the same relative position. As the plane goes faster, the treadmill speeds up, always maintaining the aircraft's relative position.

Would you ever be able to take off?

GO!!

I'm sucked in because I starting to have a hard time telling who believes what. . .

Just because someone asks a question, it doesn't mean the question itself is valid. The question has two mutually exclusive states.

If you begin to move and the plane goes faster, you could takeoff.

However, if you are in the same relative position and maintaining the aircraft's relative position, you will not fly.

 

[Stifler's Mom]

I'm imagining the ERAU campus is abuzz with this question. No shortage of guys sitting around their computers with bras on their heads, theorizing the possible outcome.

COOPERVANE...you're a bad, bad man. Look what you started.

 

[PCL_128]

another way to look at is an airboat in a river. The thrust of the airboat is from an airplane propeller.

Aim the airboat up river and give her all she's got. If the river keeps accelerating downstream as you speed up going upstream. Will you move?

If the top end of the airboat is 100kts, and the river is flowing at 100 kts the other way, will you have moved past the dock you just left on the shoreline?

Not the same situation. The river is producing immense drag upon the fuselage of the boat. In the case of the airplane, the only drag that the propeller has to overcome is the drag from the wheel bearings. This drag is virtually nothing, and increasing the speed of the treadmill won't really affect it. Once the airplane's propeller overcomes the drag from the bearings (almost immediately), then the airplane will begin to accelerate without regard for the speed of the treadmill.

 

[Flyer1015]

Oh, it's on the Internet. Must be right then.

In this case, it is right. That column, "Ask the Pilot" on Salon.com is by Patrick Smith, a regional Captain turned legacy furloughed F/O.


He brings lots of experience in his columns. They are all excellent, and he thoroughly does his research if he's presenting a question (as in this case).



You're right, everyone needs to be careful when finding answers on the internet.

But in this case, that column and that pilot are a good, credible source.