Can a Plane on a Treadmill Take Off?

Let' say it this way. The airplane is moving forward at 60 kts. Does
that make it more clear?

The airplane is moving forward at 60, the belt, using the model in the
OP, is moving backwards at 60. The wheels are turning at 120 kts. If
it's a 172 it'll lift off into, on a calm day, 60 kts of airspeed over
the wings.

It's a nicely phrased question that caught me at first as well.
Substitute real speeds into what had been posted and the answer becomes
clear to me, although a lawyer in the group might find a (ground) loop
hole.

"Dave Doe" wrote in message
. nz...
In article ,
says...
At the point where the tire contacts the ground, it's speed is
zero. 180° away, at the top, it is moving forward at twice the speed of
the
car.

Negative - yer forgetting centripetal force.

? Negative what? Talking about a point on the surface of the tire, not the
wheel as a whole. Centripital force has nothing to do with the forward
velocity of that point (how it travels in one axis).

http://www.wordiq.com/definition/Centripetal

--
Duncan

What is the conveyor belt going to push against now?

The conveyor belt is pushing against the force of the prop through the
air but we don't care. The problem stated that they are doing 80mph, we
shouldn't worry about how the plane is able to do 80mph on the belt.

-Robert

"alexy" wrote in message
...
Yes, the problem could have been made uninteresting by removing any
ambiguity. But as stated, it is very common (almost universal) to
speak of movement of a terrestrial object with respect to the surface
of the earth. If another frame of reference is intended, it is almost
always specified.

Very amusing.

According to you:

On the one hand, the problem is uninteresting if one removes the ambiguity
in the phrasing.

On the other hand, there is no ambiguity, because if a different frame of
reference were intended, "it is almost always specified".

So, the logical conclusion you arrive it in your post is that the problem is
uninteresting.

For an uninteresting problem, it sure generated a lot of traffic.

Pete

If you tie a 100 foot rope to the tail of an airplane (or some other
part of the airframe), attach it to a good strong post, and run the
propellor up to whatever rpm is available, is anyone claiming the
airplane can then lift up say a feet off the ground?

(Assuming the tail doesn't tear off)

(and, a conveyor belt under the airplane is optional)

Are you saying 1) the rope is tight, or are you saying 2) you are giving the
plane a 100' running start?


"AES" wrote in message
...
If you tie a 100 foot rope to the tail of an airplane (or some other
part of the airframe), attach it to a good strong post, and run the
propellor up to whatever rpm is available, is anyone claiming the
airplane can then lift up say a feet off the ground?

(Assuming the tail doesn't tear off)

(and, a conveyor belt under the airplane is optional)

If you tie a 100 foot rope to the tail of an airplane (or some other
part of the airframe), attach it to a good strong post, and run the
propellor up to whatever rpm is available, is anyone claiming the
airplane can then lift up say a feet off the ground?

(Assuming the tail doesn't tear off)

(and, a conveyor belt under the airplane is optional)

Depends on the airplane, certain lpanes are built in such a way that
they can actually attain enough lift just from the prop wash alone.

The Monk

If you tie a 100 foot rope to the tail of an airplane (or some other
part of the airframe), attach it to a good strong post, and run the
propellor up to whatever rpm is available, is anyone claiming the
airplane can then lift up say a feet off the ground?

(Assuming the tail doesn't tear off)

(and, a conveyor belt under the airplane is optional)

Depends on the airplane, if a plane is built in such a way that it can
actually attain enough lift just from the prop wash alone than yes.

The Monk

Jim Logajan wrote:
"cjcampbell" wrote:

Saw this question on "The Straight Dope" and I thought it was amusing.

http://www.straightdope.com/columns/060203.html


Seems Cecil Adams is compounding the confusion by having the page's title
begin:

"An airplane taxies in one direction...."

So is the plane attempting to taxi or take off? The page's title says one
thing, the person posing the question is stating another. The hypothetical
pilot of the taxing plane would presumably not let the the airspeed go to
takeoff speed, while the pilot of the plane taking off would want to
accelerate to rotation speed. So on that basis alone, we can say a taxing
plane isn't going to take off!

;-)
The earth is a treadmill. Goes about about 900 knots (at equator). Does
that bother your takeoff? Suppore treadmill stopped (rotation stopped).
Takeoffs any different, assuming you aren't launching into orbit?

BillJ wrote
The earth is a treadmill. Goes about about 900 knots (at equator).
Does that bother your takeoff? Suppore treadmill stopped (rotation
stopped). Takeoffs any different?

You forgot one major difference....in the case of the earth, the
airmass is travelling at the same 900kts, ignoring any localized
wind effect....not so in the treadmill case.

Bob Moore