Nick...
Does that mean that from the cockpit you cannot determine the nett effect or their is no nett effect ??
And obviously nobody has told the atsb that a rotor can't tell where the wind is coming from.
Ambient wind conditions can have significant and differing effects on a tail rotor equipped helicopter's performance. Engine power is delivered to a transmission system, which drives the main and tail rotors The power required to drive the transmission system is determined primarily by the amount of drag being produced by the rotors and the power available is determined by the power output of the engine(s). The difference between the power available and power required is known as the power margin. If the power required to drive transmission exceeds the amount of power available from the engine, then the main and tail rotor speed will decay, or droop. When the speed of the main rotor droops significantly, the main rotor loses lift and the helicopter descends. Wind blowing over a main rotor provides translational lift that can significantly reduce the power required to drive the helicopter's transmission system. Wind may also assist a helicopter to maintain heading, which also reduces the load demand on the transmission and therefore reduces the power required to drive the transmission. Conversely, a wind from an adverse direction may increase the load demand on the transmission and, in turn, the power required from the engine. Therefore, the wind may cause a net effect which, depending on its strength and direction, will reduce or increase the power required for a tail rotor equipped helicopter to maintain flight.