The effect of the flare in autorotation reduces the forward speed, as it does in powered flight, by tilting the Total Rotor Thrust away from the direction of flight. This gives a horizontal component of total rotor thrust, rearwards, to decelerate the helicopter. The other effect of rearward tilt of the rotor disc in the flare is to cause the inflow angle to increase. This gives an increase in the angle of attack, which produces an increase in total rotor thrust. The vertical component of this increased Total Rotor Thrust will, during the flare, increase to a value greater than the weight, and consequently the rate of descent will decrease. The increase in Total Rotor Thrust will increase the coning angle and Coriolis effect will cause an increase in R.R.P.M. Also the increased inflow angle causes the autorotative section of the blade to move outboard, resulting in a substantial increase in Rotor R.P.M. It will be seen that the larger the flare, that is the greater the change of disc attitude, the greater will be the RRPM increase, rate of descent decrease and the more rapid the reduction in forward speed.
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