It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Thank you.
Some features of ATS will be disabled while you continue to use an ad-blocker.
Originally posted by Bhadhidar
As stated before "take-off" is dependent upon lift. Lift is generated by the Bernoulli Effect resulting from air moving at higher speed over the top of the wing; thus creating an area of lower pressure Above the wing. the relatively higher pressure under the wing thus "lifts" the plane into the air.
Thrust, provided either by a propeller or jet exhaust, serves to push the wing through the ambient air at the speed required to generate sufficient lift.
If a sufficient volume of air does not flow around the airfoil of the wing with sufficient velocity (ie.: take-off speed), there will not be suffiecient lift generated to allow the plane to fly.
Speed is measurement of velocity relative to another object, generally speaking, that object is the ground. Which, although the Earth (the "ground" in this case) spins at some 3000 MPH, I believe, is generally perceived of as being stationary (Except sometimes in California!).
In the thought excercise given, the forward velocity of the plane is exactly countered by the "treadmill runway" thus negating the forward velocity of the plane. The plane would have the same velocity, therfore , if its wheels were locked and unmoving.
Originally posted by Travellar
Originally posted by Bhadhidar
You were off to a good start, but the runway will not negate the speed of the aircraft, and it's speed is relative to the air.
Originally posted by ch1466
Xerrog,
>>
Your right it will take off. A conveyor type system actually wont pull the plane back at all. It will not keep it from moving. A plane relies on air to push/pull itself forward not the wheels.
>>
WRONG.
And the proof is simple.
Assume it's a tractor-driven prop aircraft.
Say the 'P effect' of slipstream from a propellor acts against the airfoil (and fuselage) inboard of about the 1/2 span point sufficient to create lift enough for the plane to fly. If this wash is in effect the only fluidic behavior acting on the airframe as a function of 'powered lift', why waste the weight and _drag_ of the outboard span which is NOT under P Effect?
Particularly if the jet is not designed to have added maneuver much beyond 1G level flight.
Now assume it's a jet. If the wash (had damn well better be) aft of the wing /pushing/ it forward is only sufficient to keep it motionless, WHAT is generating the powered lift (propulsive fluid force directed over) ANY PART of the wings sufficient to provide lift?
Now assume it's a helicopter, if the helicopter needs only move forward at sufficient speeds that it's rotor acts as a fixed airfoil, why the wasted weight of a transmission and anti torque system to spin the main rotor for vertical takeoff?
Because the blades independent motion _faster than the forward motion of the aircraft_ is required to generate enhanced differential pressure and thus lift effect, that's why.
People like this assume that jet=thrust and thrust=lift where in, really, lift is based on relative motion THROUGH the air to create differential pressure GREATER than thrust.
Even if you are only 'pushing' with a quarter of the total mass-offset needed to push it (straight up) directly. The air holds you up. Thrust only parts it as a function of motion.
All motion in this hypothesis begins and ends with the frictional cancellation of energy through the rotational effect OF THE WHEELS. And it is their very lack of 'traction' (which is to say more torque from a motor than drag from the conveyor) _not friction_ that prevents them from ever overcoming the equal and opposed force sufficient to generate independent airfoil movement through the air.
So long as both conveyor belt and jet are cancelling each others applied forces (Newtonian Physics people) so that THE WING stays motionless, there is NO LIFT.
And no takeoff.
No matter how fast your wheels spin.
KPl.
[edit on 14-2-2006 by ch1466]
Originally posted by ch1466
As postulated, if the aircraft generates no relative motion along the length of the runway, the velocity of the airfoil _moving through the air_ will never be sufficient to take off.
Originally posted by ch1466
WRONG.
And the proof is simple.
All motion in this hypothesis begins and ends with the frictional cancellation of energy through the rotational effect OF THE WHEELS. And it is their very lack of 'traction' (which is to say more torque from a motor than drag from the conveyor) _not friction_ that prevents them from ever overcoming the equal and opposed force sufficient to generate independent airfoil movement through the air.
No matter how fast your wheels spin.
Originally posted by ShatteredSkies
Bhadhidar is completely and totally right.
If to an observor it is stationary, then no, the plane WILL not take off, but if the plane is motion to an observer despite the fact that the conveyor belt is moving against the aircraft, then it will take off, remember the landing gear does not produce lift. I think that before we can truely know the answer to this question, we have to know whether or not the if the aircraft is in motion or stationary to an observing.