theoretical background
Hi all,
first of all you have to compare apple to apple. 2 apple is not equal to 2 orange.
It is a mistake to compare 50K engine thrust with the aircraft wieght. They are acting in different planes. Thrust and drag are acting in the same plane and lift and weight are acting in another plane. This is in hand.
But to your main question how can 50K pounds lift 130K pounds.
Now let us remember F (force) = m (mass) X a (accelaration) .
So do not forget that pounds is only the mass part. There is also the accelaration. For us humans staying on the earth the accelaration is the gravity (9.81 m/s*s).
And to find the total thrust force acting on the aircraft you have to multipy it with the accelaration of the aircraft to find the force.
But do not forget that these forces are shown for the equilibirium state. That is steady level flight.
As you know from Bernoulli, the energy is constant. It only transforms from one form to another form. In case of our machine it converts the chemical energy from fuel into thrust through accelarating the air taken into the engine.
So we will make a mistake when we compare the thrust of the engines to taking 130K pounds airplane from 0knots to the air.
We have to compare the energy !
When the A/C is stopping it has no kinetic energy but potential energy. That is m (mass) x g (gravity) x h (height of the A/C).
When the a/c is airborne it has kinetic energy and potential energy. That is 0.5 x m (mass) x V * V (square of the A/C speed) and again the potential energy greater than on the runway but weight is getting less due to fuel burn.
But during this time the trust of the engine by changing the chemical energy of the fuel in to thrust . The energy of this is Thrust (in the form of Newton) x d (distance). And this energy is equal to the above mentioned energy + loss due to friction and heat loss - initial energy.
So you have to compare energy to energy. But if we are talking about a solid block standing still in the air and we do not care about how it came there and our only aim is to keep it standing still there then your comparision is corrcet.
I hope it helped.
Best Rgds,
Guclu Ulgenalp