THE disadvantages of present methods of proving engine installations by flight tests are discussed in this paper. Some data are given to show the great expense of such methods. The conclusion is reached that adequate ground-test facilities should be provided for use in pre-flight development and service tests of new engine installations.
A comparison of the results of ground tests on the Vega Ventura engine installation with flight-test results indicates some factors in ground-test technique which should be satisfied in order to insure reliable results. Similitude conditions to be met for cooling, vibration, and accelerated service tests are discussed to illustrate the method of approach for such problems. Various types of test equipment are described for attaining these conditions, the closed-return wind tunnel appearing to offer the greatest advantages for general testing. A new compact arrangement for a closed-return wind tunnel is described, which will reduce the cost of construction appreciably.
Arguments are presented in favor of the engine test wind tunnel for thorough pre-flight proving of new installations. Further data are given to show the justification for such wind tunnels, due to reductions in the cost of flight testing, as well as avoidance of delays in production, lost sales, and service replacements in the field.