This .NET class wraps the AcDbHelix ObjectARX class. 

This class implements the AutoCAD helix entity. Helix derives from Spline, but overrides the spline properties with its own behavior. Objects of the Helix class contain an embedded Spline which is wrapped by the Helix in order to constrain its behavior so that its basic shape is maintained. The behavior of calling NURB functions on the Helix class is unknown and not recommended.

Autodesk.AutoCAD.DatabaseServices.DBObject
    Autodesk.AutoCAD.DatabaseServices.Entity
        Autodesk.AutoCAD.DatabaseServices.Curve
            Autodesk.AutoCAD.DatabaseServices.Spline
                Autodesk.AutoCAD.DatabaseServices.Helix

Public Class Helix
Inherits Spline

public class Helix : Spline;

When setting the constraints on a helix object, the order in which the set functions are called is important. Refer to ConstrainType for a detailed explanation.