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An experimental study was conducted to evaluate the performance of a turbine based combined cycle (TBCC) inlet concept, consisting of a low speed turbojet inlet and high speed dual-mode scramjet inlet. The main objectives of the study were (1) to identify any interactions between the low and the high speed inlets during the mode transition phase in which both inlets are operating simultaneously and (2) to determine the effect of the low speed inlet operation on the performance of the high speed inlet. Tests were conducted at a nominal freestream Mach number of 4 using an 8 percent scale model representing a single module of a TBCC inlet. A flat plate was installed upstream of the model to produce a turbulent boundary layer which simulated the full-scale vehicle forebody boundary layer. A flowmeter/back pressure device, with remote actuation, was attached aft of the high speed inlet isolator to simulate the back pressure resulting from dual-mode scramjet combustion. Results indicate that the inlets did not interact with each other sufficiently to affect inlet operability. Flow spillage resulting from a high speed inlet unstart did not propagate far enough upstream to affect the low speed inlet. Also, a low speed inlet unstart did not cause the high speed inlet to unstart. The low speed inlet improved the performance of the high speed inlet at certain conditions by diverting a portion of the boundary layer generated on the forebody plate.

SEPTEMBER 1974ENGINEERING NOTES 589 aircraft is dry washed or polished. Total lapse time is approximately six hours. This accomplishment is credited to the specialized equipment for gaming easy and rapid access to all areas of the exterior surface.Several operators are evaluating a barrier coating over the areas of high soil exposure. This coating traps the soils on the surface without permitting them to embed in the paint. At the washing cycle, the barrier coating is released from the airplane surface by a chemical solution which is spray applied. With the release of the barrier coating, the soils are removed, leaving the regular painted surface fairly easy to clean by the conventional cleaning materials and methods. The barrier coating is then reapplied.Another two operators are reported to be flight testing a clear polyurethane topcoating which is applied over glossy, pigmented paint. Purpose of the test is to determine if the topcoat will prolong gloss retention of the pigmented surface and if it will enhance cleaning time and effort.The Military Aircraft Command is planning indoor facilities for complete washing of its C-5A fleet. Outdoor facilities will continue to be used, but hopefully limited to the washing of lower surfaces which are accessible from portable stands and standard length brushes and mops. Fraternal Approach Toward AlleviationProcedural problems are surmountable for effective, efficient cleaning of jumbo jets. In time, special equipment will be developed, as will satisfactory cleaning compounds; nevertheless, much of the developments will have to be tailored to specific aircraft configurations, cleaning locations, schedule requirements, and operational spectrum. For resolutions to the procedural problems for washing mammoth aircraft, contributions must be applied willingly from the experiences of aircraft manufacturers, operators, washing contractors, and the specialized chemical compounders. Testing and evaluating of special products and equipment are of interest to all operators; consequently, a mutual organization should have this information for assessing materials and procedures and for recommending improvements. Such an organization is the Air Transport Association, which has an active committee for aircraft cleaning. This committee has both civil and military participation. By the active participation of its members, uniformity of procedures will be promoted so that economy can be shared by all contributors. By collective action of concerned and technically capable people, the procedural problem of washing the jumbo jet will be resolved.