Can a Plane on a Treadmill Take Off?

Jesse needs to learn how to capitalize, punctuate, and separate his
sentences into paragraphs in order to make his posts readable.
\
Yep. That would be a very good start. There is more to it than that,
though.
--
Jim in NC

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

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

The question goes like this:

"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.)

Cecil Adams (world's smartest human being) says that it will take off
normally.

Assuming the increased tire friction doesn't cause a problem the aircraft
should take off but have twice the normal tire rotation speed when becoming
airborne. That's because the thrust is produced by the prop and it will
accellerate the aircraft into the relative wind. The conveyer belt is just
an entry to confuse the issue. For a car the situation would be completely
different since it produces forward motion by the tires which contact the
moving conveyer belt. The car wouldn't move at all.
--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
-

The answer is an obvious YES. I don't know how this thread got as big
as it did :^)

The Monk

"Darrell S" wrote in message
news:rT6Ff.24873$jR.14387@fed1read01...
[...] For a car the situation would be completely different since it
produces forward motion by the tires which contact the moving conveyer
belt. The car wouldn't move at all.

It might. As "Doug" points out, the presentation is ambiguous as to the
reference point for the speed of the vehicle. If one uses the ground (and
stationary portions of the treadmill) as a reference, then the car would
move, just as the airplane does (it would have to in order to comply with
the description given in the problem), and the car's speedometer would
register a speed twice its actual speed relative to that reference.

Pete

Robert M. Gary wrote:
Only if there is an 80 mph tailwind.


If the plane is rolling 80mph against a conveyor going 80mph back the
difference would be zero.


BUT-what is the total friction force from the wheels? Certainly it's
less than the thrust from the engine--I mean, that's what wheels are
designed for, to have as little rolling friction as possible. So let's
add this up... forces acting on airplane are thrust, aerodynamic drag,
and an essentially negligible amount of drag from the wheels. Add it
up, and since the thrust is greater than the drag (as it would be on a
normal takeoff) the airplane accelerates. As I said in another post,
since wheels are designed for minimal friction, just pretend that they
are frictionless, and therefore not even there (anti-gravity airplane).
What is the conveyor belt going to push against now?

Why dont we look at it from another direction !!!

If the treadmill is moving at 60 MPH in one direction and the trust is
set to pull 60 MPH in the oppisite direction, the plane would be
neither moving forward or back.

so the only thing that is moving is the wheels, the wings are not
generatring any lift becuase they are not moving in a positive
direction, the wings dont know that the wheels are going like a bat out
of hell !!! the wings still things its standing still. you WILL NEED TO
HAVE FORWARD MOMENTIUM to generate lift.....

the only lift the wings will get is downwash from the prop.

and i used the word STUPID not to offend anyone, but i am right in what
i said about the aircraft. but its really fun to talk about this after
over 75 messages posted...

Because it is interesting, and evokes thought.

"Flyingmonk" wrote in message
oups.com...
The answer is an obvious YES. I don't know how this thread got as big
as it did :^)

The Monk

"cjcampbell" wrote:
"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?"

One critical detail is missing that makes in impossible to say "yes" or
"no":

Is the forward speed of the plane above the stall speed?

The plane could, after all, being moving forward at 10 mph. Nothing in the
problem statement above precludes that speed, or any other. HOWEVER, the
question on the web site asks "_Can_ the airplane take off?" The answer to
that one is, using the most common meaning of the word "can," essentially
"yes". What a difference substitution of one word makes!

;-)

"Flyingmonk" wrote in message
oups.com...
The answer is an obvious YES. I don't know how this thread got as big
as it did :^)

Obviously, the answer is not so obvious! What surprises me is that there are
more than TWO opinions!!! :-)
You would think that the airplane would either take off or it wouldn't!?!
Anyway, reading/participating in this
thread is much more interesting than reading the usual flames in various
newsgroups. It's surprising and refreshing
that this thread, with so many posts, hasn't (yet) degraded into a
flame-fest. )

The Monk

"The Flying Scotsman" wrote

so the only thing that is moving is the wheels, the wings are not
generatring any lift becuase they are not moving in a positive
direction, the wings dont know that the wheels are going like a bat out
of hell !!! the wings still things its standing still. you WILL NEED TO
HAVE FORWARD MOMENTIUM to generate lift.....

Man, you are about as dumb as a fence post, or bag of rocks, or.......PLONK
--
Jim in NC