Are Two Always Better Than One?

In every new aircraft design project, the ideas, concepts and desires are generally reflected in the initial tradeoff studies to achieve the customer's requirements in the best possible manner. Part of the difficulty during the early stages of the design process is the "translation" of the customer's requirements into terms that can be quantitatively addresssed in the preliminary designs. The more general the foundation requirements are, the more difficult the preliminary design process becomes, for the most part. It would seem that this is due to the broader range of concepts that "may" satisfy the customer's requirements. There are several categories of parameters that affect the design of a new aircraft to different magnitudes. The most critical category is the one whose parameters are basic to mission performance and are mandatory for the most basic conceptualization of the design. Two of the obvious parameters in this category are the number of pilots and engines. One other parameter which is not so obvious is the level of protection for the crew (i.e., survivability, crashworthiness, etc.). The implications or effects of each of these parameters, although quite strong as far as the design is concerned, are dependent on the synergistic interaction with a broad range of other parameters. As such, isolating a few of the key parameters for discussion certainly can not be complete since the myriad of other parameters will not be included. It is the intent of this paper to present a few of these parameters to illustrate some of the tradeoffs from the flight crew standpoint.