Refer to figure.
From figure 3.44, the Distance D4 and the Climb gradient can be determined with the helicopter flying with OEI, Climb speed V_Y and landing gear retracted for a given pressure altitude, temperature, take-off mass and wind conditions:

• Enter with the pressure altitude 0 ft from the top left graph and move vertically up until OAT +15°C (ISA).
• Continue horizontally to the right crossing the 7500 kg take-off mass line.
• Move vertically down until the 10 kt wind.
• Continue to the right and read Climb Gradient: 18%.

NOTE:
According to EASA AIR OPS - CAT.POL.H.105 - General, accountability for wind shall be no more than 50% of any reported steady headwind component of 5 kt or more. But, CAP 758 is under JAR OPS and does not take into account the 50% factor for the reported headwind component.

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