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This paper describes the systems analysis and design of an automatic temperature control system in the world's largest fluid dynamics testing complex consuming 470 megawatts of drive power. The plant treated in this paper can be described mathematically as a 110th order system having 130 feedback loops. Facility component characteristics are mostly non-linear, with prominent distributed parameters and ten long, variable fluid transport delay times. Important simplifications introduced to make the analysis and design work tractable include: (a) Application of the mathematical analogy between the theory of electric transmission lines and gas flow to validate the separation of temperature and pressure variations, (b) Selection of control frequency to permit lumped-parameter representation, (c) Design and construction of special computer devices and circuitry to simulate transport delays from 0.2 to 141 seconds in length. These valid simplifications reduce the plant to a 14th order system having about 50 feedback loops. The simplified system is simulated on an analog computer for economical synthesis and design of the controllers.