To ensure integrity of the Loran-C radionavigation system during non-precision approaches, an automatic blinking system notifies the user when the system is not functioning within specifications. To be certain that timely detection of this blinking can be guaranteed, one of the requirements imposed on an airborne Loran-C receiver is that it should flag an alert when the signal to noise ratio drops below –6 . This paper addresses some blinking detection methods, that will ensure safe operation beyond this –6 dB limit. A preliminary version of this article was presented at the Wild Goose Conference in Birmingham, August 1992.