This disk contains both the source code and the compiled basic program 
to design an aircraft propeller based upon aircraft and engine performance 
data.  The program is an extended version of the technique outlined in my 
presentation to members of EAA Chapter 106 in October 1990.  The extensions 
allow the user to vary the angle of attack (alpha), which affects the blade 
chord, and the tip velocity, which affects the prop diameter.  Several blade 
planforms are also provided for variety.  In addition, an effort is made to 
allow for degradation due to tip-loss. The approach is substantially the same
as one used by John Roncz in a presentation he made at an Oshkosh forum some
years back, and material garnered from a variety of aerodynamic textbooks
in which the defining equations were:

        Lift          L = 1/2(rho)(b)(Cl)(Vro)^2(l)(chord)
        Thrust        T = Lcos(Phi0) - Dsin(Phi0)
        Drag          D = 1/2(rho)(b)(Cd)(Vro)^2(l)(chord)
        Torque        Q = [Lsin(Phi0) + Dcos(Phi0)](Omega)
        Alpha         a = angle of attack
        Theta         0 = angle of induced velocity
        Phi             = Tan^-1[(V/Omega)(r)]
        rho             = air density
        r               = radius
        V               = forward speed 
        b               = Number of blades
        Beta          B = a + 0 + Phi   (PITCH ANGLE)
        Pitch           = Tan^-1(Beta)
        
     The program has been distributed world-wide and has not been subjected to 
any harsh criticism to date.  It has also been used as part of a lab course at 
Bucknell university.  However; no guarantees are offered or implied.  The 
design procedure is based upon sound engineering fundamentals and is offered 
to the fraternity in the spirit of comradeship.  I would be pleased to 
receive any helpful suggestions, results achieved, or errors uncovered,  
whether they be typographical or a result of faulty reasoning on my part.  
In any event, good luck to all.

                                    Edwin A. Dokus
                                    EAA 51432
                                    5-14-99




 
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