Psychological mechanisms required by some technical-engineering occupations, and corresponding requirements to the training routines are discussed. It is shown that they demand adequate development of operational technical thinking which in its turn is based on coexistance of a number of representations of a technical object facilitated by a "levelling-off" mechanism which reduces the impact of unfixed representations; the core of the technical thinking process consists of an image of a normally-functioning-object which provides for conscious fixation and selective procession of only those representations that are needed in order to solve a current problem. In training therefore technical objects must be represented as structured and purposeful systems.