Abstract: An apparatus operable to seal an opening in an aircraft fuel tank during a pressure test of the fuel tank is described. The apparatus includes a substantially dome shaped body having a perimeter. The body further includes a rim extending in an orthogonal direction about the perimeter and a flange extending in a normal direction from the rim and about the perimeter. The flange is sized to engage the fuel tank about the opening. The apparatus further includes a sealing gasket proximate an intersection of the rim and the flange, extending completely around the perimeter. The seal is oriented to provide a sealing function between the fuel tank and the body as pressure is increased within the fuel tank.

Abstract: A ball or plug valve comprises a ball or plug having a through bore which is rotatable in a metal body to control the flow of fluid through a passage in the body. The ball can be rotated from the exterior of the body by means of a metal stem which is rotatably received in an opening in the metal body. The opening is stepped so as to define a first shoulder which faces the passage in the body, and the stem is correspondingly stepped to define a second shoulder which faces the first shoulder. Under normal operation of the valve, the shoulders are spaced apart slightly and a sealing ring is interposed therebetween. In the event that the sealing ring fails, the pressure of fluid in the passage presses the shoulder on the stem into contact with the shoulder on the body to create a metal-to-metal seal which prevents the escape of fluid to atmosphere through the opening. To make the seal reliable, the shoulders are shaped so that they contact each other only over the outer periphery of the stem shoulder.

Abstract: A screenable and strippable solder mask composition which contains a polyepoxide or polyimide/amide; a detackifier and a high-temperature resistant filler; and use thereof for protecting predetermined areas on a substrate from the solder deposition.

Abstract: A corrugated horn antenna adapted to be coupled to a waveguide at the apex thereof for X-band excitation is further adapted to be connected to waveguides through a circumferential slot for S-band excitation at four distinct phases S.sub.1 through S.sub.4 selected for the desired S-band polarization. The circumferential slot is positioned along the axial length of the horn for good impedance matching and is provided with an X-band choke in the form of two concentric choke slots. For further improvement in impedance matching, the second (outer) choke slot is divided by plugs into four segments that coincide with waveguide ports for the four distinct phases of the S-band.