Can a Plane on a Treadmill Take Off?

If you restate the problem as follows the aircraft will obviously NOT
fly.

The aircraft is on a conveyor belt.

The conveyor is programmed to move in such a way as to maintain the
aircraft at an airspeed of zero as measured at the pitot.

propwash?

No - It's a Skymaster and the examiner cut the front engine.

Oh-wait - It's a jet...

a.


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.

"jesse" wrote in message
oups.com...
My friend and i were discussing this. There is not enough information
in the orginal question to determine anything.

I think jesse has earned his way into my "not worth the effort" file.
Anyone else have him strike you that way?
--
Jim in NC

wrote:

If you restate the problem as follows the aircraft will obviously NOT
fly.

The aircraft is on a conveyor belt.

The conveyor is programmed to move in such a way as to maintain the
aircraft at an airspeed of zero as measured at the pitot.

Absolutely, if you CHANGED the problem, and restated it as above, then
it wouldn't fly. Another way to state your entirely different problem
is to say that the conveyor is set up to always move at a speed that
maintains the wheel speed of the plane as the same as the conveyor
speed.

Or to parallel the original problem, "a conveyer belt that moves in
the opposite direction to the way the plane is pointed, at exactly the
speed that the airplane' wheels are moving, so that the plane is not
moving"

This will require a VERY fast conveyor, since once power is applied
and the brakes are released, it will have to move fast enough that the
rolling friction of the tires and bearing friction in the wheels
offset any thrust provided by the plane's propulsion system. Sounds
about as possible as any other conveyor belt runway!

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.

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

"alexy" wrote

Reread the stated problem:

"a conveyer belt that moves in the
opposite direction at exactly the speed that the airplane is moving
forward."

All it is, is a trick question, aimed at testing your reading and
comprehension ablility. The plane moves off in exactly the same manner as
on a regular runway. The moving belt is a distracter.
--
Jim in NC

"Doug" wrote in message
oups.com...
There will be airspeed felt by the plane in the area of the propellor
wash. Out of the prop wash, since the plane is not moving relative to
the surrounding air, there will be no relative wind felt by the
airplane. The airplane MIGHT take off, but it will not be a normal
takeoff, at least not for a normal airplane with 36' wingspan and a 6'
propellor. I really don't think there is enough information to know the
answer for sure. Too many unknowns.

This is one of these "frame of reference" problems.

Re-read it, Doug. The plane is not getting its motion from the wheels, so
it matters not what the wheels or wheel speed is doing.
--
Jim in NC

Of course! the plane does take off! revelation!! if you kept the
throttle low enough to equalize drag on the wheels from the belt, you
wouldnt go anywhere. Firewall it, youre outta there! like a touch n go,
if you have the throttle retarded when you touch down, your in a
similar state, wheels spinning, add throttle you accelerate, even
though the runway increases the speed of the wheels. doesnt matter if
you start out at zero KIAS, KTAS, GS or any other. the prop applies a
force to the surrounding air, the wheels spin freely underneath you, of
a take off occurs... ok, its so simple. if the conveyor matches the
wheel speed so what, youre off still. if it matches air speed, so what
youve got rollers to get you off that spinning track! cool, i get it
now... my bad ....

Look..... for all you people that think that the plane will take off.
Whats the point in having CAT Launching systems on aircraft carriers
priced at billions of dollars a piece... they could just pop down to
wallmart and buy a treadmill and the aircraft will not need to use any
runway what so ever........

DONT BE STUPID....

IT CANNOT BE DONE !!! IF IT CAN BE THEN SOME CLEVER BUGGER 50 YEARS AGO
WOULD OF DONE IT BY NOW..

plus, has anyone thought what will happen to that aircaraft if i does
manage to generate enough lift..... ITS GOING TO HAVE NO AIRSPEED,
stall and fall out of the sky like a brick.

Simple physics lads...

Wow, this is too hard to stay away from. New scenario. Same conveyor.
Instead of airplane, i hold in my hand a toy car with freespinning
wheels. If you can agree that thrust from the prop/turbine would be
akin to my hand pulling on the toy car then this will work. It is a
force acting outside of the conveyor. I start to pull the toy car, the
conveyor starts moving backwards at an equivilant speed. so what? my
hand is still pulling the car forward at say one MPH, the belt moves
back wards at one MPH... the belt is only putting a slight amount of
resistance on the car through the friction of the wheels, but nothing
that my hand(or prop etc) cant over come.... i keep accelerating the
car and the belt does too, the wheels see 2 X my forward speed, i can
increase this accelration until the wheel fall off, or untill the car
grows wings or whatever. if the car can accelrate with my hand, so can
the plane using thrust against the air. there it is. one of the amazing
things about this is that some very intelligent people have completely
different views of this. Have yall checked out the boards at straight
dope?

another example, say im on a skate board facing bakwards with a fan....
same thing, the fan pushes against the air and forth do go I.
weeeeeeeeee!

what force exactly does the conveyor hold you back with? the only force
i see is the friction in the wheels, and a negligible amount of power
from even a O-320 will overcome that. really... that and wind
resistance is the only force keeping you in one spot. If your thrust is
greater than that, newton prevails....

it just took me a while to sort it all out... have fun, stay up too
late!
Jester

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.

Yes.
The problem states '..moves in the opposite direction at exactly the speed
that the airplane is moving
forward..' So the plane is moving forward, thus it will fly. The wheels
are just spinning at 120mph instead of the usual 60mph.

"pilot" wrote in message
oups.com...

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.