Why does a helicopter have different vertical flight regimes if T = G in all the regimes?

Answer 1. The equality T = G is approximate. It does not take into

account the effect of the parasite drag force X. With account for this

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force in hovering, climb, and descent T ~ G + X But the parasite drag

force will be different in the different regimes: it will be greatest in a

vertical climb and least in a vertical descent. Therefore, the thrust is

actually greater than the weight during climb and less during descent; in

hovering T = G + X.

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Answer 2. All the vertical flight regimes are characterized by absence of vertical acceleration, i. e., constant vertical velocity. According to the law of inertia, the acceleration will be zero if no force acts on the body.

The equality T = G is equivalent to the equality T – G = 0, which means that it is valid for all regimes.

But in the different regimes the rotor performs different work; in

climb the main rotor work N. = T(V. + V ); in hovering N. = TV.; in descent

x і у x 1*

N_^ = T(V_^ – Vjeg) ; therefore, more power is required for climbing than for hovering and descent.