The geometric characteristics of the air screw include: the shape of the blades in plan view, the shape of the blade profile, the diameter, the angle of inclination of the blade and the geometric pitch of the screw. According to the shape of the blade in plan view the screws can be very diverse. The blades of the lifting air screw are the most responsible and loaded units of an aircraft, providing the creation of required lift. It must meet diverse and controversial requirements, such as:
- ensuring the requirements of static strength: the stresses acting in the blade spar from centrifugal forces in flight and from mass forces in the parking lot shall not exceed the permissible stresses;
- providing the necessary stock at flutter;
- no resonance oscillations;
- providing the necessary resource;
- ensuring sufficient stiffness of the blade on the bend in in-planes of traction and rotation, as well as torsion;
- obtaining high aerodynamic qualities;
- providing low (by resource) cost and technological effectiveness.
The blade developed according to specified requirements allowed to create a screw of new design.