1. ANGLE TO INLET, DEG JETVELOCITY. FTISEC 1750 2360 1750 2360 1750 2360 PREDICTION. REFERENCE 10 MEASUREMENT RR1 MEASUREMENT RR2 1.8 2.0 0.9 1.3 2.1 3.6 MEASUREMENT RR3 1.5 1.3 2.2 2.6 3.2 Figures 18and 19show thecorrespondinxl'fil, field shapes: thc formeralso shows the drdured airframenoisr fieldshapcs 31 172 and 250 kf. plus thc RR3 field shape with the engines 91 idlr speed. This curve effectively represents the RR3 noise "floor" and isrelatively closeto thecase forjet velocity of 1750ft SCP.
2. The test program whose results have been described in this paper was conducted essentially for research purposes and to demonstrate the effectiveness in flight of thesuppressorlejector concept. The actual application ofsuch a Configuration to a production aircraft requires further. extensive development programs to optimize thedesign and to integrate it into a particular aircraftlpower plant arrangement,
3. CONCLUSIONSIt has been demonstrated that the use of an acoustically lined ejector in conjunction with multi-element suppressor nozzles gives considerably increased attenuations compared with the suppressors alone, The ejector benefit is greatest at jet velocities above 1600 ftisec: at lower velocities. some forward arc noise increase can occur, The acoustic performance of the ejector can be reasonably well predicted on the basis of model and statictest results; the shortfall in the performanceofthe 8- lobe nozzleiejector configuration compared with prediction may have been due to imperfectmixing within theejectortube. Any improvement madeheremight alsoreducetheforward arcnoise increase, which wasparticularly evidentwith thisconfiguration, and also affect the apparent increase in airframe noise associated with the ejector. Considerably more work is also required tounderstand the effectsof flight on the suppressor configurations, which behave somewhat differently from the referenceconicalnozzle. The current test program has demonstrated that mechanical suppressoriejectorsystemscan he designedforAST application which have both efficient sound suppression and propulsion performancecharacteristics. A major conclusionfromthetesting is that carefully tailored suppressor system designs can result in negligiblelossof suppression with forwardvelocity.