Question

As a designer our task is to generate fuselage through conic lofting method. If an intermediate C/S shape is elliptic then, what should be the appropriate value of conic shape parameter?

(a) 0.4142-0.5

(b) 0.7

(c) 0.8369

(d) 1.2-1.5

I had been asked this question during an interview.

My question is taken from Configuration Layout in portion Configuration Layout and Loft of Aircraft Design

Answer 1

The correct answer is (a) 0.4142-0.5

Best explanation: Given, intermediate cross section = elliptic.

Conic shape parameter CSP = DS / DC, where D = midpoint of line drawn from end point A to end point B, C = tangent point, S = shoulder point.

When CSP = 0.4142 and AC = BC then it will generate circular shape.

Now, when CSP = 0.5 it will produce parabola. Hence, to generate elliptic cross section value of CSP should be between 0.4142 and 0.5 based on our requirement.