Can a Plane on a Treadmill Take Off?

"BDS" wrote in message
m...

"Michael Ware" wrote

Yes, but an airplane isn't propelled by its feet.

This is where everyone who seems to think that the airplane will fly is
getting confused.

The method of propulsion doesn't matter. You can drive an airplane down
the
runway by driving its wheels just like a car and it will still reach
takeoff
airspeed and fly briefly. The propeller is only important once you are
airborne, because you need something to pull you through the air.

And all this time, I thought it was the propellor that made the airplane
move across the ground. I stand corrected.

The bottom line is this - you cannot take off without first moving across
the ground unless the wind (airmass movement relative to the ground) is
blowing hard enough to give you sufficient airspeed to fly without moving.
In this case, once you take off your airspeed will immediately begin to
decrease unless you are using a prop to pull you through the air, or a
tether to hold you there (relative to the ground).

What do you mean, 'unless you are using a prop to pull you through the air'?
How does your airplane work?

Example - a floatplane is sitting in a river that is moving at 30 mph
(hey,
it's a fast river!). There is also a wind blowing down the river at 20
mph.

If the floatplane is anchored and facing into the wind, it has an airspeed
of 20 mph. If you release the anchor and use enough engine power to get
the
plane going through the water upstream at 30 mph you will be standing
still
with reference to the shore, and your airspeed will be 20 mph. If the
river
was flowing at a rate in excess of the maximum speed of your airplane,
then
you could never move forward going upstream with reference to the shore,
and
your airspeed would never exceed 20 mph, even at full throttle. If you
fully understand this then you would know that you could shut your engine
down, face downstream, and take off and fly briefly.

This is not an anology. With the wheels turning on the treadmill, friction
(and thus the force exerted) are negligible. The force exerted by the
running water on the floats is much greater.

BDS

"BDS" wrote in message
m...

"Michael Ware" wrote

Yes, but an airplane isn't propelled by its feet.

This is where everyone who seems to think that the airplane will fly is
getting confused.

The method of propulsion doesn't matter. You can drive an airplane down
the
runway by driving its wheels just like a car and it will still reach
takeoff
airspeed and fly briefly. The propeller is only important once you are
airborne, because you need something to pull you through the air.

The bottom line is this - you cannot take off without first moving across
the ground unless the wind (airmass movement relative to the ground) is
blowing hard enough to give you sufficient airspeed to fly without moving.
In this case, once you take off your airspeed will immediately begin to
decrease unless you are using a prop to pull you through the air, or a
tether to hold you there (relative to the ground).

Example - a floatplane is sitting in a river that is moving at 30 mph
(hey,
it's a fast river!). There is also a wind blowing down the river at 20
mph.

If the floatplane is anchored and facing into the wind, it has an airspeed
of 20 mph. If you release the anchor and use enough engine power to get
the
plane going through the water upstream at 30 mph you will be standing
still
with reference to the shore, and your airspeed will be 20 mph. If the
river
was flowing at a rate in excess of the maximum speed of your airplane,
then
you could never move forward going upstream with reference to the shore,
and
your airspeed would never exceed 20 mph, even at full throttle. If you
fully understand this then you would know that you could shut your engine
down, face downstream, and take off and fly briefly.

BDS

BUT... the initial condition, as stated in the OP, is that the
river(conveyor) is moving at the same
speed as the airplane but in opposite directions. So, with a 30 mph
river(conveyor) and a
20 mph headwind the airspeed would be 50 mph. The plane is moving at 30 mph
in the opposite
direction with respect to the shore(runway). The airplane would then be
travelling upstream at 60 mph
relative to the rivers surface. The only difference between the river
example and the conveyor example is how firmly the airplane is
coupled to the conveyance. The floats/river scenario would require more
thrust to overcome the resistance
than the wheels/conveyor example. Same mathmatics, different numbers. The
floatplane just needs a bigger motor.

Nice article explaining this:

http://www.avweb.com/news/columns/191034-1.html

Flyingmonk wrote:
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


Yeah Monk that airplane is called a helicopter.

"The Flying Scotsman" wrote:

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...


Ok, now suppose the treadmill is on the moon. . .

(ducks)

However the airspeed-vs-wheel-rotation argument works out,
I think it is worth pointing out that all this time on the treadmill
should result in a _significant_ loss of weight for the aircraft,
resulting in more useful load.

Category and class of aircraft...
aircraft includes all types of flying machines.

AIRPLANE does not include helicopters, see FAR Part 1

ASEL ASES AMEL AMES the A means category airplane and the
rest is the class
AMEL B747 includes the type.

Rotorcraft is the category and helicopter is the class.

--
James H. Macklin
ATP,CFI,A&P

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.



"601XL Builder" wrDOTgiacona@coxDOTnet wrote in message
news:43E62B1E.6080403@coxDOTnet...
| Flyingmonk wrote:
| 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
|
|
| Yeah Monk that airplane is called a helicopter.

"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.

On Sun, 5 Feb 2006 00:39:47 -0800, "Peter Duniho"
wrote:

"Flyingmonk" wrote in message
roups.com...
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.

Other than the ones we call helicopters, I've never heard of such a thing.

Care to elaborate?


I've been told that a Maule will do that. With a little wind, just
apply power and it jumps into the air instantly. Similarly, in wind
it'll land vertically. But then the Maule pilot who told me this was
from Alaska, where airplanes routinely perform mythic feats.

RK Henry

"Peter Duniho" wrote in message ...
"Flyingmonk" wrote in message oups.com...
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.

Other than the ones we call helicopters, I've never heard of such a thing.

Care to elaborate?
Tilt wing... Osprey?
Ducking and running! :' )

Joe Schneider
8437R



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