Paphitis wrote:kurupetos wrote:Isn't it true that the heavier the aircraft the more thrust it will need to take off?
Therefore aircraft mass & thrust are interdependent.
No that is not entirely correct.
There are 4 forces acting on an aircraft.
They are:
1) Lift (L) - acts upwards and at right angles to the airflow through the Centre of Pressure
2) Weight (W) - is the total weight which acts vertically downwards through the Centre of Gravity
3) Thrust - is the forward propulsive force provided by the engines
4) Drag - is the backward force which opposes the forward motion of the aircraft and acts parallel and in the reverse direction of the aircraft movement
For an aircraft to maintain straight and level flight, then L=W.
For an aircraft to climb then L>W.
Lift can be worked out using the following formula:
L=1/2 x rho x Vsquared x s
rho=air density
V=Velocity
S=Wing Area
Therefore to increase L you will need to increase the velocity (V), and to do this you would
need additional Thrust. So yes, if you are carrying a full load, you would need maximum thrust to climb out.
However this does not necessarily apply to aircraft of greater mass, because some large aircraft can have a massive wing span and wing area (S) which also creates greater L as:
L is directly proportional to S
L is directly proportional to VThat is why some aircraft with a small Delta Wing (Mirage 2000) require a massive amount of V to lift off, whereas a heavy C130 Hercules can TO a low speeds and use a small amount of runway due to its large wing area (S) creating more lift at lower speeds.
Have I confused you yet? 
