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## Main Question or Discussion Point

Hello Forum,

I understand that an airplane can fly when its overall weight ##W_{plane}## (force pointing down) is perfectly balanced by an upward directed force called lift ##F_{lift}##. If the lift is larger than the weight, the plane will rise in height.

When the airplane is empty and starting from rest on the runway, the plane eventually reaches the right speed ##v_{max}## to generate lift ##F_{lift}## and make the airplane fly. The lift is larger than the weight when the plane takes off: ##F_{lift} > W_{plane}##. Is that correct? If weight and lift were immediately equal, the plane would not gain altitude. Once in the air, the pilot can either increase or reduce the lift force compared to the weight (which stays constant).

What if the plane had a load so that its total weight was ##W_{total} = W_{plane}+W_{load}##? The airplane max speed ##v_{max}## that it can reached on the runway is still the same and dictated by the plane's engine and its fixed power. With load or without load, the pilot always pushes the engines to the maximum. My understanding is that the lift force, always bigger than the total weight, will still be sufficiently large (up to a certain maximum load) to lift the airplane.

If correct, how much larger is the lift force compared to the weight of the airplane when the airplane is empty? 20% bigger? If so, if the airplane weighted ##1000 N##, the overall lift force would be ##F_{lift}= 1200 N## the max loading capacity must be less than ##200 N## so that the lift force remains larger than the overall weight...

I understand that an airplane can fly when its overall weight ##W_{plane}## (force pointing down) is perfectly balanced by an upward directed force called lift ##F_{lift}##. If the lift is larger than the weight, the plane will rise in height.

When the airplane is empty and starting from rest on the runway, the plane eventually reaches the right speed ##v_{max}## to generate lift ##F_{lift}## and make the airplane fly. The lift is larger than the weight when the plane takes off: ##F_{lift} > W_{plane}##. Is that correct? If weight and lift were immediately equal, the plane would not gain altitude. Once in the air, the pilot can either increase or reduce the lift force compared to the weight (which stays constant).

What if the plane had a load so that its total weight was ##W_{total} = W_{plane}+W_{load}##? The airplane max speed ##v_{max}## that it can reached on the runway is still the same and dictated by the plane's engine and its fixed power. With load or without load, the pilot always pushes the engines to the maximum. My understanding is that the lift force, always bigger than the total weight, will still be sufficiently large (up to a certain maximum load) to lift the airplane.

If correct, how much larger is the lift force compared to the weight of the airplane when the airplane is empty? 20% bigger? If so, if the airplane weighted ##1000 N##, the overall lift force would be ##F_{lift}= 1200 N## the max loading capacity must be less than ##200 N## so that the lift force remains larger than the overall weight...