Can a Plane on a Treadmill Take Off?

"The Flying Scotsman" wrote in message
ups.com...
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.

You are implying that because the treadmill is spinning the wheels at 60mph,
that the treadmill is therefore exerting a force equal and opposite the
thrust generated by the propellor neccesary to propel the plane forward at
60mph. That is incorrect.
The force that the treadmill is capable of exerting on the mass of the
aircraft through the wheels is negligible.

you WILL NEED TO
HAVE FORWARD MOMENTIUM to generate lift.....

WOW, I must have missed that in ground school.
You need airflow across the wings to generate lift. Which, because the plane
is moving forward as stated in the question, is present.


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.

Apparently you are the only one that thinks so.

"The Flying Scotsman" wrote:

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.
Why. What's keeping it from moving forward if the thrust is set for a
thrust that would normally move it forward at 60mph. And besides, you
just said that the plane is moving neither forward nor backward. The
statement of the problem is that the conveyor moves at the same rate
and opposite direction as the plane. Since you say the plane is not
moving, I guess neither is the conveyor. Do you really think that is
what the poser of the question intended? g

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

On Sat, 04 Feb 2006 16:10:16 GMT, "Travis Marlatte"
wrote:

As posed by the question, I agree that the belt is a distracter. However, it
is not irrelevant as the thrust applied to achieve flying speed must
overcome not only the normal tire rotation friction but twice that. That the
plane will fly presumes that there is enough excess thrust to do just that.

So long as the bearings don't melt or seize, there's not much (if any)
extra "rotation friction" at double the normal takeoff speed.
Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

It's surprising and refreshing
that this thread, with so many posts, hasn't (yet) degraded into a
flame-fest. )

Amen to that!

The Monk

"Doug" wrote:

The whole problem is confusing because
"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."

Moving forward with respect to what? The conveyor belt? (you gt the
answer that it WONT take off), or the air? (you get the answer that it
WILL take off).

AMBIGUOUS!!!

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. Two movements are mentioned in the problem. Is
there any reason to suspect that one is movement relative to surface
of the earth (the conveyor) and the other is movement relative to the
first object? Why not th other way around, in which case the conveyor
is just an ordinary runway?

If you are not willing to resolve that ambiguity by assuming
conventional frames of reference, you might as well assume that one is
speaking of velocities relative to a solar system frame, in which case
the plane may be going very very fast forward, backward, sideways, up,
or down, depending on time of day and orientation relative to the
earth. The problem makes a lot more sense assuming conventional use
of "moving".
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

"The Flying Scotsman" wrote in message
ups.com...
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.

You are implying that because the treadmill is spinning the wheels at 60mph,
that the treadmill is therefore exerting a force equal and opposite the
thrust generated by the propellor neccesary to propel the plane forward at
60mph. That is incorrect.
The force that the treadmill is capable of exerting on the mass of the
aircraft through the wheels is negligible.

you WILL NEED TO
HAVE FORWARD MOMENTIUM to generate lift.....

WOW, I must have missed that in ground school.
You need airflow across the wings to generate lift. Which, because the plane
is moving forward as stated in the question, is present.


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.

Apparently you are the only one that thinks so.

All,
I read some of my posts in response to comments made about me. The
spelling, punctuation, and grammar mistakes are all because of my
blatant laziness, and excitement to get my post out. The comments I
made about the gun and the crowd seemed a bit disturbing to me when I
read through them. I should have picked a better example. Please do not
take those comments as some subconscious plea. I have been through
several hefty background checks in at least two states and the latest
for the Department of Defense that went back to when I was a teenager.
I admit that I was wrong initially about the answer to the question.
After working through it via the posts, discussions with my friend, and
my own reasonings, I changed my mind. I hope that in the future if you
all see my posts you will not regard me as some crazy loon. I have been
following r.a.s since late 2000 and think it is a priceless source of
information and support. Many people helped my as I was going through
my private pilot training, and I appreciate that. I hope that when I
begin my instrument training that people will be just as kind and
helpful. Thank-you.
Jesse

P.S. I could always chalk it up to the chemicals at work. Maybe my Mom
dropped me on my head when I was a baby, you never know!

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. Two movements are mentioned in the problem. Is
there any reason to suspect that one is movement relative to surface
of the earth (the conveyor) and the other is movement relative to the
first object? Why not th other way around, in which case the conveyor
is just an ordinary runway?

If you are not willing to resolve that ambiguity by assuming
conventional frames of reference, you might as well assume that one is
speaking of velocities relative to a solar system frame, in which case
the plane may be going very very fast forward, backward, sideways, up,
or down, depending on time of day and orientation relative to the
earth. The problem makes a lot more sense assuming conventional use
of "moving".

Yes, the frame of reference has everything to do with the answer ...and the
riddle!
Since the original post refers to an airplane taking off you should conclude
that
"air" (the atmosphere) has to be included in the mix and that an airplane
does it's
flying relative to the world/atmosphere. Then it is not unreasonable to
assume that the riddle
implies that the most logical reference frame is the planet and that the
conveyor and the plane
are moving in opposite directions with respect to that stationary observer.
The only requirement
then is that the airplane move fast enough to take off and that the conveyor
move fast enough "backwards"
to match the airplanes speed (only to satisfy the specified initial
conditions even though the speed of
the conveyor is entirely irrelevant to whether or not the airplane takes
off.) It doesn't even matter if the wheels
need a bearing job or if the plane is on skids or if the brakes are set.
Either the engine generates enough thrust
to overcome resistance and accelerate the plane to take off or it doesn't.

Kpi$LyLcEhRo wrote:
/snip/

PS:If you would like to know, I'm an engineer and an airline pilot!
Jeeeeezus!


Q: How do you know if there is an (airline pilot/engineer) at a party?

A: Oh, he'll tell you!

Happy Flying!
Scott Skylane

In article ,
says...

"muff528" wrote in message
news:OW2Ff.179$DV2.5@trnddc07...

.....OR relative to each other? If so, there could be just enough thrust
applied to overcome frictional
forces and the airplane doesn't move relative to the world so airspeed is
0.

That would have to be either a very underpowered airplane, or wheels with a
lot of friction.

BUT WAIT!!! .... ANY two objects can be said to be moving (or not) at
equal
speeds relative to each other. A point
on the conveyer belt moving east at 4mph and a jet moving west at 600mph
each have a relative velocity of 604

But there's the trick. A treadmill belt isn't really moving at all, it's
turning.
Try this for a brain scrambler. Think about a tire on your car, driving down
the highway. 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.

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

--
Duncan