Rotary Wing Blade of an Aircraft, and Aircraft Provided with such a Blade

A blade for a rotary wing of an aircraft, the blade being able to rotate about an axis of rotation of the rotary wing and about a pitch axis, the blade extending along the pitch axis from a first end to a second end, the blade comprising a blade body having, along the pitch axis, a blade root and then a main part formed by a succession of sections substantially perpendicular to the pitch axis, the blade root being provided with an origin section forming the first end, the main part extending along the pitch axis from an initial section to a final section forming the second end, the final section being located at a distance equal to a predetermined rotor radius of the axis of rotation, each section extending along a transverse axis from a leading edge to a trailing edge separated by a maximum distance constituting a chord, each section of the blade body having a geometric twist angle with respect to a reference section located at a distance from the axis of rotation equal to 70% of the rotor radius,

• wherein:
• the initial section is disposed at a distance from the axis of rotation of between 20% and 30% of the rotor radius;
• the chord of the sections increases from the origin section to a maximum chord reached in a first section located at a first distance from the axis of rotation of between 75% and 80% of the rotor radius, then decreases in accordance with a law having firstly a slow decrease to a second section then secondly a rapid decrease, the second section being located at a second distance from the axis of rotation of between 80% and 95% of the rotor radius, an average aerodynamic chord dimensionless with respect to the rotor radius being between 0.05 and 0.08, the maximum chord dimensionless with respect to the rotor radius being greater than the average aerodynamic chord dimensionless with respect to the rotor radius and between 0.06 and 0.1;
• the sections have a relative thickness which decreases from the origin section to the initial section by a relative thickness of between 0.25 and 0.70 to a relative thickness of between 0.12 and 0.15, the main part having, from the initial section to an intermediate section, a constant relative thickness or a relative thickness which decreases and is then constant, the main part having a relative thickness which decreases moving away from the intermediate section to a relative thickness of between 0.07 and 0.08 in the final section, the intermediate section being at a distance from the axis of rotation of between 65% and 85% of the rotor radius;
• the angles of geometric twist increase continuously from the origin section to the initial section from a minimum negative angle to a maximum positive angle and then decrease with a first gradient of between −9° divided by the rotor radius and −13° divided by the rotor radius to a third section located at a distance from the axis of rotation of between 70% and 80% of the rotor radius, then with a second gradient egal or higher than the first gradient to a fourth section located at a distance from the axis of rotation of between 88% and 90% of the rotor radius, then with a third gradient less than the first gradient to the final section;
• and
• an offset distance separating the pitch axis from a quarter-chord line for each section decreases from the origin section to the initial section, this offset distance being constant in the main part from the initial section to a rupture section and then decreases, the rupture section being at a distance from the axis of rotation of between 80% and 95% of the rotor radius R.