Abstract: A light cover has a transparent element manufactured from polycarbonate and an infrared filter angled so as to reflect infrared radiation emitted from a light source way from both the transparent element and the light source.

Abstract: The entire contents of these applications are incorporated herein by reference. A method and apparatus for detecting and monitoring fractures in a structure by monitoring acoustic energy transmitted within the structure by receiving continuously over a period of time electrical signals from a plurality of acoustic tranducers carried by the structure in a pulse processor to form data bursts from pulses in the signals and deriving, for each of a plurality of the data bursts, delta-t values representing the differences between burst arrival times at each sensor, the delta-t values forming a delta-t pattern, and generating a damage indication signal when the delta-t pattern is repeated to a predetermined degree.

Abstract: Apparatus and a method for inspecting a topology of a surface (2) of a structural member (1) are provided. The degree to which a known type of stress has been applied to the member may be ascertained using a Moiré grid (8). The method involves providing a range of calibration samples of structurally equivalent members, the samples each having been subject to the known type of stress to a differing respective degree. Measurements taken using the apparatus and method of the invention are then compared with measurements taken from a calibration sample to determine the amount of stress which has been applied.

Abstract: A method and apparatus for detecting and monitoring fractures in a structure by monitoring acoustic energy transmitted within the structure by receiving continuously over a period of time electrical signals from a plurality of acoustic tranducers carried by the structure in a pulse processor to form data bursts from pulses in the signals and deriving, for each of a plurality of the data bursts, delta-t values representing the differences between burst arrival times at each sensor, the delta-t values forming a delta-t pattern, and generating a damage indication signal when the delta-t pattern is repeated to a predetermined degree.

Abstract: A method of measuring load applied to a pin bearing and a pin bearing arrangement for use on an aircraft landing gear are provided. Relieving one or more of two adjacent bushes (4, 5, 6) bearing on a pin (1) of the pin bearing to create a zone of constant shear stress enables measurement of load and avoids cutting the pin.

Abstract: The invention provides a method of testing a metal component (1) for cold compression of the metal when used, for example for fatigue enhancement. The component defines a generally smooth surface (6) and includes a region (22), eg an aperture, subject to cold compression which breaks that surface in a given area. The method includes the steps of placing a moire grid (13, 15) such that it is spaced from and coextends with the said area of the surface, directing a source of generally parallel light (16) through the grid (15), and at an oblique angle thereto, at the said area of the surface, and viewing the surface through the grid substantially normal to the surface whereby to observe any light interferences fringes (24) caused by eruption of the surface due to cold compression of the metal.