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It should be particularly noted that because of the aforementioned overlap the REACTION half of the engine's working cycle becomes the ACTION half of the Aircraft's, Air Mass Motion System.
Important Note: It is this overlapping interaction between the ACTION and REACTION halves of the Aircraft's, Air Mass Motion System throughout the engine which so dramatically reduces the efficiency of the transfer of the Air Mass Motion Energy (Gross Thrust) invested in the Aircraft's Air Mass Motion System at all demand conditions, to a Net Thrust Value.
Gross Thrust = (EmVj) where (Em) is the engine mass flow per second and (Vj) is the engine's final propelling nozzle velocity in (ms -1)
Net Thrust = (EmVj - EmV) where V is the RESULTANT Aircraft Velocity at any in flight condition. In other words:
Net Thrust = The Thrust force of the ACTION half of the Aircraft's Motion Cycle "(EmVj)" minus the negative thrust force of the REACTION half of the same System - "(EmV)"
Note: In terms of Drag losses incurred these are already accounted for in the RESULTANT Velocity that the Aircraft can achieve at any condition.
Note: It should be remembered that the overall DRAG losses incurred in flight are if fact caused by two entirely different factors.
Consider: Friction, Form, Profile Drag and Induced Drag are incurred in the ACTION half of the Aircraft's Motion System simply because in this half the Aircraft is doing work upon the Air Mass formed by the atmosphere through which it is caused to fly; these a losses unavoidable and required by nature and are as accounted for in physics as the price to be paid for such an ACTION.
Consider: Induced DRAG for example is created in the REACTION half of the Aircraft's Motion System because here the local Air Mass surrounding the Aircraft and formed by the atmosphere is caused to do work upon the Aircraft by imparting to it a Lift Force. Here also, is incurred Inlet Momentum Drag caused by an Air Mass formed from the Atmosphere being caused to ram into the physical structure of the Aircraft at a speed which cannot be accommodated fast enough to avoid incurring in direct accordance with the laws of physics, a shattering deceleration resulting in the creation an equally dramatic and equivalent negative thrust force acting against the Aircraft's line of flight.
Point: Of all of the DRAG forces incurred in flight those incurred in the ACTION half of the Cycle together with that of Induced Drag in the REACTION are truly legitimate aerodynamic Drag losses. This is not so in the case of Intake Momentum Drag. This is caused by the simple fact that the inlet to the engine compressor forms the forward boundary face and "Frame of Motion Reference" across which the ACTION and REACTION Air Mass Motion halves of the Aircraft's Motion Cycle meet.
Point: The Intake Momentum Drag which is a major thrust loss, reference the associated "Case File" for explanation is, not the result of our failure of obey any law of physics but, our failure to more intelligently utilise Newton's, 3rd Law of Motion.
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