Mahira isnt no 😀

Christabel is – The one that sings the rhyme about “Disco Stick” …. 😀

yeah cheers guys lol I worked it out just as I was falling alseep last night 🙂

DP – Thanks for explaining it 🙂 I dont appreciate being told to put my brain in gear, all ive done is completely overthink the experiment.

Saw that experiment – Imo its a rubbish example of this experiment, varying rates of acceleration between the conveyor belt and aircraft etc.

So far I came up with this (rather sarcastic) theory

Right, I’ve gone away and thought about this some more and I still come up with the same conclusions as I did earlier on although slightly edited

In answer to the original question “Will the plane take off or not” My answer is now

Theoretically – No the aircraft will not lift
However it would be impossible to conduct the experiment in a 100% controlled environment

I’ve taken the time to think about this and to type it up so that my opinions/points of view and theories could (hopefully be) best understood, all I ask it that you read through it carefully before making any comments :thumbs:

A plane is standing on a runway that can move (some sort of conveyer belt). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction).

Can the plane take off?

Difficult question

Before I go any further I want to make sure that we all understand the difference when I say “Closed” and “Open” systems

A system is commonly defined as a group of interacting units or elements that have a common purpose. The units or elements of a system can be cogs, wires, people, computers, and so on. Systems are generally classified as open systems and closed systems and they can take the form of mechanical, biological, or social systems. Open systems refer to systems that interact with other systems or the outside environment, whereas closed systems refer to systems having relatively little interaction with other systems or the outside environment.

In this case – Closed system = No variables etc we are imagining the experiment at its simplest.

Again, please take some time to read this before saying “pfft load of crap” :thumbs: Im taking some time and effort to explain what I percieve this experiment to be.

Firstly I can say that the reason the mythbusters experiment worked is because of the multitude of variables that are not taken into account in conducting the experiment.

The exact wording from the experiment imo illustrates that – conveyor belt and aircraft, not only have the exact same acceleration but the exact same velocity. The mythbusters experiment has already gone wrong here, as there is no way for the rate of acceleration of the car to match that of the aircraft. As a result the aircraft was able to gain momentum and airflow over its wings and lift. They also chose an aircraft in its design that would utilise the airflow over its foil from the prop to its maximum effect.

So to completely simplify the experiment down to the key point – is there any airflow going over the wings.

Prior to the introdcution of the aircraft, lets first imagine when you go running on the treadmill at the gym – this is EXACTLY the same principle as the question that has been asked above – you’re running at whatever speed relative to the treadmill but you arent moving forwards through the air. You are effectively running on the spot

Lets look at this from the point of view of a closed system/experiment.

Closed System
In this thought experiment, let us imagine the following. There is no wind, the air is perfectly still, the manner of propulsion of the aircraft, be it turbine or prop does not cause any air to flow over the wings at all (in real life, this is negligable anyway) for this experiment “friction = 0”

So, lets put our aircraft on the conveyor belt, the aircraft accelerates to 1mph and stays there, at the exact same moment, the conveyor belt accelerates in the opposite direction to 1mph and stays there. Rate of acceleration for aircraft and conveyor belt are both equal. Has the aircraft moved from the point upon which it was placed on the conveyor belt?

The aircraft is technically travelling at 1mph in relation to the conveyor belt. However it speed relative to the ground/air about it is 0mph.

When you run on a treadmill at 10mph – you are running at a speed of 10mph on the treadmill, but at a speed of 0mph relative to the ground, do you feel air moving past you when you run on a treadmill no because you arent moving through the air you are running on the spot.

So let have the aircraft and conveyor belt now accelerate to the takeoff speed lets say 150mph :nod: the rate of acceleration is the exact same until both arrive at 150mph, at this point the aircrafts speed relative to the stationary conveyor belt is 150mph, however it speed relative to the ground and the air surroungind it is still 0mph – taking from where I said above that we arent assuming that the engines are providing a flow of air over the wings – then as a result there has been no airflow over the wings at all.

As I have already ountlined using the formula for lift

L = (1/2) d v2 s CL
• L = Lift, which must equal the airplane’s weight in pounds
• d = density of the air. This will change due to altitude. These values can be found in a I.C.A.O. Standard Atmosphere Table.
• v = velocity of an aircraft expressed in feet per second
• s = the wing area of an aircraft in square feet
• CL = Coefficient of lift , which is determined by the type of airfoil and angle of attack.

(1/2)d.v^2.s.CL = L
IF v=0
Then
L=0

As if you multiply anything by 0 or have any active component of a formula such as this at 0 – your outcome will be 0
Definition of lift

Lift is created by a difference in pressure between two surfaces – in an aerofoil (wing/propellor) it works by forcing the air on the top surface to travel faster (further to travel) than the lower surface. The result is a considerable difference in pressures between the upper and lower surfaces resulting in the wing being sucked up into the air due to lower pressure on the upper surface

From this we can deduce that to create lift in any form from an aircraft wing, we need an airflow.

So in this closed system – would the aircraft takeoff? No as above. Is this experiment realistic? No.

Open System

Concerning the open system, there are a whole shedload of variables to take into account.

To name a few
• Unnacountable airflow from – wind/engines etc
• Multiple types of friction – friction of air against the aircraft as a structure, friction of the tyres with the conveyor, friction of the wheelbearings with the spindles
• Density of the air

+ a great shedload of other variables that are uncontrollable

If we take the mythbusters example as supplied by Rubix :thumbs: this is an open system – the rates of acceleration were different between the aircraft and the conveyor, no account was taken for windspeed and the design of the aircraft was such that would allow the prop wash to assist the wing in producing lift :nod: the same would apply should you use turbines to power your aircraft, however obviously the amount of air sucked over the wing cause by the intake of the engines would be dependant on their placement. Wing mounted, tail mounted etc.

To summarise, in a perfectlty controlled experimental world, the aircraft would not lift, in the real world however it is a different matter. You could improve upon the experiment greatly to make it as close to controlled as possible and then you would be closer towards proving the theory of the experiment that I outlined above :nod:

But… No one is going to spend millions of pound to prove someone else in the internet wrong! :wack: