These five basic reasons explain why the turbojet and turbofan propulsion systems have caused a revolution in aircraft design and in our concepts of the way in which aircraft may be effectively used.
[234]...deploying wing spoilers after the aircraft is on the runway. This technique is routinely used on many Jet-powered transports. (See the section on high-lift systems at the end of this chapter.)
[235]...shells. A cascade is an array of closely spaced, highly cambered airfoils and is used for changing the direction of airflow; it may also be thought of like the blades of a compressor of constant chord laid out parallel to each other rather than radially about a single axis. The clam shell closes the exhaust nozzle and diverts the gas flow outward and forward.
....long fan duct installations. (Figure 10.7 was taken from reference 185, which contains a comprehensive summary of basic information dealing with acoustic treatment for noise suppression.) An experimental application of acoustic treatment to the nacelle of a first-generation, low-bypass-ratio turbofan engine is shown in figure 10.8. Most modern high-bypass-ratio engines employ some form of acoustic treatment. The splitter rings shown in figure 10.7 have not been used in any production installations for a number of practical operational reasons, such as possible difficulties in deicing and the possibility of the rings....
....being broken by foreign object ingestion with subsequent damage to the rotating parts of the engine.
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[244] and low supersonic speeds. For flight at Mach numbers much beyond 1.6, however, variable-geometry features must be incorporated in the inlet if acceptably high inlet pressure recoveries together with low external drag are to be achieved. This complication is dictated by the physical laws governing the flow of air at supersonic speeds. The nature of supersonic flows is not discussed here, but two variable-geometry inlets are illustrated in figure 10.10. Shown at the top in figure 10.10(a) is the D-type side inlet used on the McDonnell Douglas F-4 fighter. Evident in the photograph are the large fixed diverter plates that also serve to begin compression of the entering flow. The adjustable ramps provide further compression along with the desired variation of throat area with Mach number. The angle of the ramps varies automatically in a prescribed manner as the Mach number changes.
...in between, and utilizing the resultant turbine efflux to propel an aircraft was uniquely that of two men working independently with no knowledge of the other's work. These men were Frank Whittle in England and Hans Joachim Pabst von Ohain in Germany.