Detector for helicopter blade crack indicator

An improved beta radiation detector housing for a system for indicating cracks in a hollow aircraft blade wherein a pressure differential is maintained within the blade with respect to the ambient atmosphere and for operation in the presence of strong electromagnetic fields and beta radiation, the system including

• a pressure sensor means for mounting on the blade in communication with the interior of the blade and having a member moveable between a first position for a higher pressure differential and a second position for a lower pressure differential,
• a beta radiation source mounted on the member with the beta radiation source disposed for radiation transmission to a detector when the member is in the second position,
• a beta radiation detector means for mounting on a nonrotating portion of the aircraft in a position to receive beta radiation from the beta radiation source and electromagnetic radiation from other sources, and
• circuit means having the output of the detector means as an input and providing an output varying as a function of the position of the member for indicating the pressure condition within the blade,
• said housing comprising:
• an enclosure of an electrical conducting material and having an open side and means for supporting the beta radiation detector means therein and exposed to radiation passing through said open side;
• a cover for said open side, said cover having a window for passage of electromagnetic and beta radiation;
• an electrical conducting sheet means having apertures therethrough, with said sheet means providing for blocking electromagnetic radiation for protecting said detector means from electromagnetic radiation while said sheet means at the same time provides for passing beta radiation particles permitting detection of beta radiation;
• and
• means for attaching said cover to said enclosure with said sheet means therebetween.