Abstract: An apparatus for detecting and measuring changes in the shape of a wall of a body includes a detector capsule adapted for attachment to the wall and pneumatically connected to a volume transducer responsive to changes in the internal volume of the apparatus produced by changes in the shape of the wall. The internal volume of the capsule is partially defined by a flexible diaphragm for engagement and complementary movement with the wall. The capsule contains a resiliently deformable material which presses the diaphragm into contact with the wall regardless of the convex or concave shape of the wall.

Abstract: Apparatus for aligning an aircraft landing aid projector of the type which comprises a light source located at the focus of a parabolic reflector, a lens mounted coaxially with the parabolic reflector and a filter disposed intermediate the reflector and lens close to the focal point of the lens. The apparatus comprises a base having a surface portion for supporting a projector, a lens for focussing light from the projector onto an image receiving means and means allowing observation of the image receiving means. The filter of a projector is correctly positioned when it appears in focus on the image receiving means.