Impulse / Momentum Flow

Graphic: Newton's Cradle

Into the "general" static air pressure, a moving wing accelerates air downwards - now it becomes dynamic. This momentum / impulse is passed on to the air and within it, called impulse flow. Due to the compressibility and viscosity of the air, thereby areas of different air pressure form around the source (wing/airfoil/glider...).

This applies not only to the wing, but in principle to all bodies such as the fuselage, provided there is a certain angle of attack in relation to the flight path. Without an angle of attack there are no pressure differences, without pressure differences there is no resulting force. Newton's laws, known as axioms, formulate the relationships between inertia, impulse and reaction. Every action causes an equally large reaction. Therefore it can be said:

Even if interactions occur simultaneously, one can still speak of a causal chain because there must always be a triggering moment and and a impulse in the mechanical sense is transmitted with a certain deceleration).

By lift, however, we don't just mean any upward force, but at least one that is strong enough to achieve an acceptable descent rate. Better still, a horizontal flight or climb (with the support of muscle power, motor, thermals). This requires conditions such as the discussed angle of attack, the necessary speed and air with its characteristics. An equilibrium must be established for each stable flight condition. We could interweave the conditions into the causal chain mentioned above or extend it, but this would not change the core statement.