Can a Plane on a Treadmill Take Off?

"jesse" wrote in message
ups.com...
"One of the posters raised the issue of what would happen when the
aircraft
returned for landing."

If the belt were moving backwards at the speed of the aircraft when it
touched down, it would be similar to landing with that much tailwind,
basically, your ground speed would double you airspeed at touch down.

All that would happen is that the wheels would have to turn faster to
accomdate the treadmill. Just as they do at takeoff. There's not really
any difference between the two scenarios.

"BDS" wrote:

Maybe he's not so smart after all :)
Maybe not, but smart enough to see this one.

On a calm day you can run and feel a wind on your face because you are
moving across the ground as well as through the air. But, if you run on a
treadmill there will be no wind because you are not moving through the air -
the air is calm so it has no relative motion with respect to the ground.
Neither do you when you run on a treadmill.
True. Irrelevant, but true.

Assume the airplane is on the conveyor and there is a 10 kt headwind, and
assume we need 60 kts for takeoff. The only way to generate the additional
50 kts of airspeed is by moving across the ground at 50 kts.
Right so far.

If the
airplane is standing still
Hold that thought...
because the conveyor is moving backwards at the
same speed that the airplane is moving across the ground at
Skip back up to see what speed you say the airplane is moving across
the ground. Then go back to the original question and figure out what
speed the conveyor must be moving when the airplane is not moving.


If the conveyor keeps the airplane standing still relative to the ground,
then it cannot take off.
Yeah, but the original statement of the problem made no such claim.


--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

"alexy" wrote

If the conveyor keeps the airplane standing still relative to the ground,
then it cannot take off.
Yeah, but the original statement of the problem made no such claim.

Alex - here is what the statement said:

"An airplane on a runway sits on a conveyer belt that moves in the
opposite direction at exactly the speed that the airplane is moving
forward. Does the airplane take off?" (Assuming the tires hold out, of
course.)

The plane cannot move forward - that means that it is standing still to me.

BDS

"BDS" wrote in message
m...


"An airplane on a runway sits on a conveyer belt that moves in the
opposite direction at exactly the speed that the airplane is moving
forward. Does the airplane take off?" (Assuming the tires hold out, of
course.)

The plane cannot move forward - that means that it is standing still to
me.

BDS


You are taking the statement 'a conveyer belt that moves in the opposite
direction at exactly the speed that the airplane is moving
forward' to mean that somehow there is a force being applied to the mass of
the aircraft, equal and opposite the thrust generated by the propellor. The
only place the treadmill can exert any force an the airplane is the only
place the treadmill is touching the airplane: the wheels. Any motion of the
treadmill belt will be translated into rotation of the wheels. This will not
prevent the aircraft from moving forward, through the air and taking off.

("Michael Ware" wrote)
You are taking the statement 'a conveyer belt that moves in the opposite
direction at exactly the speed that the airplane is moving forward' to
mean that somehow there is a force being applied to the mass of the
aircraft, equal and opposite the thrust generated by the propellor. The
only place the treadmill can exert any force an the airplane is the only
place the treadmill is touching the airplane: the wheels. Any motion of
the treadmill belt will be translated into rotation of the wheels. This
will not prevent the aircraft from moving forward, through the air and
taking off.


THE AIRPLANE WILL NOT MOVE. (That's my vote)

The rotating wheels + gravity (Thank you Sir Isaac!) ANCHOR the plane to the
treadmill. Plane/prop move forward, treadmill/wheels fall back. The plane is
attached to the wheels. Try it in front of you with a ruler and a magic
marker.

That airplane is doing 150 mph down that runway, only the runway is really a
treadmill which is matching that speed. End result is = to an Olympic
sprinter on the same treadmill - I can stand next to him for his entire 10
second (27 mph) race.


Montblack 83.7
(I thought some of double-digit people needed to be heard from. g)

"BDS" wrote:


"alexy" wrote

If the conveyor keeps the airplane standing still relative to the ground,
then it cannot take off.
Yeah, but the original statement of the problem made no such claim.

Alex - here is what the statement said:

"An airplane on a runway sits on a conveyer belt that moves in the
opposite direction at exactly the speed that the airplane is moving
forward. Does the airplane take off?" (Assuming the tires hold out, of
course.)

The plane cannot move forward - that means that it is standing still to me.

If the plane does not move forward, how fast is the conveyor moving?
Hint: "a conveyer belt that moves in the opposite direction at exactly
the speed that the airplane is moving forward."

--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

Maybe he's not so smart after all :)

On a calm day you can run and feel a wind on your face because you are
moving across the ground as well as through the air. But, if you run on a
treadmill there will be no wind because you are not moving through the air -
the air is calm so it has no relative motion with respect to the ground.
Neither do you when you run on a treadmill.


D*mn you're dumb. Oh sorry, was I thinking out loud? A thousand
pardons. :^)

The plane is NOT powered at the wheels! In this case the plane will be
going 60kts forward relative to the surrounding air and 120kts forward
relative to the treadmill. Think about it.

The Monk

On 4 Feb 2006 20:45:34 -0800, "Flyingmonk" wrote:

The plane is NOT powered at the wheels! In this case the plane will be
going 60kts forward relative to the surrounding air and 120kts forward
relative to the treadmill. Think about it.

I reckon that's true, given the question posed in "The Straight Dope,"
(I've been too lazy to read it myself, but I gather from the other
responses that what you say above is what Adams had in mind.) but what
is the point of the original question in that case? Is it just to
trap a sloppy reader into thinking it's all about a crackpot VTOL
methodology?

The more interesting question is whether you could land real short by
using the treadmill.

Don

The more interesting question is whether you could land real short by
using the treadmill.

The treadmill is irrelevant; it is the relative wind that matters.
Whether you are standing on solid ground or on a treadmill, if you have
a head wind of 60kts, you will be airborne period.

The Monk

"Don Tuite" wrote in message
...
but what
is the point of the original question in that case? Is it just to
trap a sloppy reader into thinking it's all about a crackpot VTOL
methodology?

I think the more interesting point is to notice the implications of not
transmitting force through the wheels. Even people who know that planes and
cars differ in that way may fail (at least at first) to draw the appropriate
conclusion about what happens to the treadmill plane when it applies takeoff
power.

--Gary