The Heinkel commercial airplane, H.D. 40
This 1927 technical report from the NASA Technical Reports Server documents the Heinkel H.D. 40 commercial biplane, written for aeronautical engineers and aviation analysts. Its pictures pair line drawings of the plane's plan, front, and side views with photographs of the finished aircraft from several angles. A designer could draw on the clean, measured orthographic layouts and the sharp contrast of the grey airfield photographs for vintage aviation graphics.
