At the start of the commercial jet age, speeds rose to 450 knots. Today s turbofans cruise at average speeds of around 500 knots, and the Concorde reaches 1350 knots. Aviation designers and regulators must address complex challenges, given the operating conditions encountered by aircraft and the correspondingly stringent technical and airworthiness requirements that must be met. Aircraft are more severely constrained by volume and weight considerations than ground-based forms of transportation, placing more stringent limits on available technology choices. Aircraft systems are typically more complex than other transport modes, and many physical and chemical effects associated with them are closely coupled and interdependent.
Time scales for technology development and product life are on the order of decades.
As with any other commercial product, the impact of technology changes on cost and customer satisfaction must be carefully assessed. Considering the breadth and complexity of the technology base supporting today s aircraft, this chapter cannot hope to provide more than an overview of the subject. Broadly, advances that reduce the weight and drag of the aircraft fall into the first of these two categories. Engine technology is more complex. These two aspects of engine design are dealt with in Sections 7.4 and 7.5 .