BuAer, as part of the process of defining types of aircraft needed, was already using its drafting rooms to make design studies, including three-view drawings, performance calculations and, sometimes, wind tunnel data. After basic decisions were made, BuAer began sending the drawings and data to industry as part of informal design competition. Thus, the companies could either propose their own designs or develop an airplane based on the BuAer design. After they responded, BuAer evaluated their proposals, usually selected one or more for development, and issued contracts for complete design data and prototype airplanes.
In the late 1930s, BuAer stopped putting three-view drawings in the design competition package. Losers
sometimes complained that they were not chosen because they had not slavishly followed the whims of BuAer's designers. Eliminating the drawings not only freed BuAer from that charge, but also eliminated any tendency among company designers to copy a BuAer design rather than use it as guidance in thinking creatively about the Navy's problems.
To obtain improved models of an existing design, a product improvement, or evolutionary, path was followed: new engine, changes to armament, improved structure, changes requested by squadrons, etc. For example, the 1934 XBT-1 (see “Naval Aircraft,” NANews, Sep-Oct 89) through product improvement became the SBD that in -5 and -6 configurations served as a firstline dive-bomber into 1944 and in less demanding roles for the duration. In contrast, the TBD-1, developed the same year, received only minimal improvements and was in production for only two years. Thus, it was outdated by December 1941 and was replaced in mid-1942 as soon as the vastly superior TBF became available. Product improvement was important in aircraft designs that remained in production over a period of years.
