A study was made to determine the probable causes of deterioration of each of several adhesives in bonds to stainless steel at temperatures from 400 to 550 degrees F. Prellminary studies of aluminum surfaces on which ions of metals used in staLnless steel were introduced showed that iron was probably catalyzing a thermal deterioration of the adhesive. The resistance of FPL-878 adhesive to thermal deterioration at 550 degrees F on steel was improved signiffcantly by treating the steel surface to be bonded with either zinc or cerium naphthenate and firing at 1,200 degrees F. The addition of manganese dioxide to the adhesive also increased its resistance to thermal deterioration. A study of the thermal-aging properties of five different chemical types of adhesives on stainless steel and alumina revealed that a phenol-nitrile rubber adhesive was superior to a phenol-epoxy adhesive on steel, but this order was reversed on alumina. These and other observations indicated probable specific relationships among the chemical structure of the adhesive, the metal adherend, and the resultant thermal stability of bonds after aging at high temperatures.

A flight investigation at subsonic speeds of a method to improve the damping of lateral oscillations by means of a viscous damping cylinder used in the rudder system in conjunction with adjusted hinge-moment parameters has been conducted. The damping device has been applied to a modern fighter-type jet-powered airplane. The rudder was made to float with the relative wind by the addition of trailing-edge strips. In order to amplify the floating tendency (by reducing the restoring moment), a highly geared balancing tab was incorporated. Lag of the motion of the free rudder with respect to the yawing of the airplane was introduced by means of a small viscous damping cylinder linked to the rudder.

Summary: Power spectral methods of analysis are applied to flight test measurements of the strain responses of a large swept-wing bomber airplane in rough air in order to determine the effects of airplane structural dynamic on the strain responses. Power spectra and frequency-response functions of the strain responses are determined and compared with the estimated results for a quasi-static reference airplane condition. The results obtained indicate that the bending and shear strain responses are significantly amplified in rough air because of the effect of structural dynamics by an amount that varies from 10 to 20 percent at the root to about 100 percent at the midspan station. The amplifications appear to be larger for the high-altitude tests than for the low-altitude tests. The amplifications of strains appear to be predominantly associated with the excitation of the first wing-bending mode, although at the outboard stations and particularly for the shear strains significant effects also are introduced by high-frequency structural modes. The determination of airplane frequency-response functions for responses to atmospheric turbulence from measurements in continuous rough air involves a relatively new application of random-process techniques. The results obtained appear to be subject to errors from a wide number of sources which give rise to distortions and sampling errors. A general analysis of the reliability of such frequency-response function estimates is presented and methods of estimating the distortions and sampling errors are developed. These methods are applied to the data in order to establish the reliability of the present results. The results indicate that with due precaution reliable estimates of frequency-response functions can be obtained.

Overall sound-pressure levels and frequency spectra of the noise emitted from a full-scale, 7.2-foot-diameter, 3, 500 rpm, three-blade, supersonic propeller mounted on a turbine-powered airplane have been obtained under static conditions at stations about the propeller at a 100-foot radius.