Abstract: A cover for a pressure sensor for indicating cracks in a hollow aircraft blade, the sensor having a shaft carrying a radiation source, with the shaft sliding in a housing between a first position with the radiation source within the housing and a second position with the radiation source external of the housing, the cover including a sleeve for positioning around the sensor and having an open end for engaging a shoulder of the sensor and having a closed end spaced from the sensor when the open end is engaging the sensor shoulder, and a plunger slidably mounted in the closed end and movable between an outer position and an inner position, with the plunger out of engagement with the sensor shaft when in the outer position and engaging the sensor shaft when in the inner position to move the shaft into the sensor and reset the sensor, with the sleeve being of a material absorbing the radiation of the source.

Abstract: A tank content gauging system including a plurality of radiation sources and a radiation detector mounted at a fuel tank, with the radiation detector positioned for receiving radiation from the sources and for producing an output which is an electrical analog of the detected radiation, a register for storing the detector output, a telemetry-on-demand switching unit for starting and stopping the detector operation from a point distant from the tank, a transceiver for sending "on" and "off" commands to the switching unit and receiving telemetry data from the register, a computer having the telemetry data and reference data as inputs for producing an output representing the quantity of fuel in the tank, and a display for indicating the quantity of fuel in the tank.

Abstract: A system for indicating cracks in a hollow aircraft blade, such as a helicopter blade. A system wherein a pressure differential is maintained within the blade with respect to the ambient atmosphere and including a pressure sensor for mounting on the blade in communication with the interior of the blade and having a member which moves in response to pressure changes within the blade, a beta radiation source mounted on the member and disposed for radiation transmission to a detector, a beta radiation detector for mounting on a nonrotating portion of the aircraft for receiving radiation from the source, and circuitry having the output of the detector as an input and providing an output which varies as a function of the position of the pressure sensor member for indicating the pressure condition within the blade. An improved beta radiation detector housing which substantially eliminates detector sensitivity to radar transmissions while maintaining sensitivity to nuclear radiation in the beta range.