What Engineers Know and How They Know It: Analytical Studies from Aeronautical History [Paperback]

Vincenti cites several examples from the aeronautics industry. While these descriptions take on an anecdotal character, these collected narratives nonetheless impose his conclusion as well as any philosophical essay could and probably better. In each case, _What_Do_Engineers_Know_?_ demonstrates that incomplete information may yield intermediate results having little or no effect on the intended problem.

The first example relates to a wing design for the B-24. The history of the Davis airfoil design is explained, as well as its incorporation for the B-24 wing. At the time of its adoption, various airfoil shapes had been investigated, and the Davis form subsequently was found to resemble the high performance laminar-flow airfoil. But did this form benefit the B-24 performance. Probably not, answers the author. Laminar flow can be difficult to maintain at the Reynolds numbers typical of modern aircraft, particularly in wartime conditions when surface roughness will likely increase tripping the boundary layer to turbulent (with resulting increased drag -- laminar flow has a thinner boundary layer, but is more prone to flow separation). The B-24 was considered a fine aircraft, in part due to its wing length.

The second example describes flying-quality characteristics and relative design priorities regarding stability and control. (The Wright brothers had emphasized stability in the infancy of manned powered flight.) Designers had to determine what characteristics made an airplane desirable to pilots, and which would consign them to the scrapyard. This ergonomic study evolved as pilot and aircraft capabilities expanded in speed and flight duration. An appendix provides qualitative criteria used to compare stability performance.

The third example compares how thermodynamics is treated by physicists and engineers. The latter employ control volume analysis as developed by Ludwig Prandtl for economy and accuracy rather than the understanding of nature governing thermal energy transfer. The fourth example covers data collection for airplane propellers. Subtle changes in camber, pitch and twist in a design can have subtle or profound effects on efficiency. These were evaluated using empirical studies, in contrast to a more analytical treatment where the contributing second and third order effects are more difficult to distinguish. The fifth example explains the struggles in riveting thin metal sheets with countersunk joints for aircraft production. The establishment of standard head angles required more detailed material behavior for both rivets and attaching sheets than previously known.

Finally Vincenti concludes with a synthesis on how design knowledge develops from functional collections of information. The writing style can be tedious at times, and other times smooth, but this is a matter of personal taste for the reader. While a typical engineer may find some aspects of the work, particularly among the examples, more familiar than other chapters, it nonetheless remains a beneficial insight into how engineering knowledge is acquired, organized and utilized to address the concern at hand.

Vincenti describes how aeronautics technologies grew and went through their stages, and this has given me insight into my own. This is not a book of idealized process for implementing technology. It is s set of historical case studies, some of which Vincenti himself participated in, others of which he researched.

The book is not easy to read, but I have found it very rewarding. It is full of technical terms and heavy technology. At the same time, if you pay the price in effort and study this book carefully, you will not be disappointed. You will see how technologies develop, and knowing this, you will be able to anticipate developments and needs in your own area of growth.