Abstract: Method and apparatus for detecting icing, particularly on airfoils such as helicopter rotor blades, by detecting warming caused by latent heat released as water freezes. The sensors may be multiple or single, contact or remote.

Abstract: A substantially fluid orientation insensitive, simple, relatively inexpensive gauge for measuring the quantity (mass/volume) of a liquid, such as fuel, stored in a tank subjected to low gravity conditions is disclosed. The gauge comprises, in general, a transmitter and a receiver coupled to a liquid storage tank in which a liquid of known dielectric behavior, such as fuel for a space vehicle, is stored. The transmitter comprises an R.F. oscillator for generating R.F. energy across a predetermined variable frequency range. The transmitted R.F. energy is coupled to an antenna inserted into the tank and is also coupled to an R.F. energy detector. The receiver measures the received power as a function of frequency above and below the dominant resonant frequency, or harmonics thereof. The measured power decreases substantially before and after resonance because, at resonance, most of the power is absorbed or stored in the cavity and less is transmitted to the receiver.

Abstract: Method and apparatus for measurement of ice thickness employing ultra-sonic pulse echo technique, wherein an ultra-sonic pulse is emitted from a transducer at the ice-accreting surface of a structure, the pulse is reflected at the periphery of the accreted ice and the reflection is detected. The time delay is calibrated and related to ice thickness and accretion rate.

Abstract: A system which prevents the formation of ice on the external surfaces of aircraft structures by heating impinging atmospheric supercooled water droplets to above the freezing point by the transmission of microwave electromagnetic energy to the droplets which if unheated would freeze upon impact and adhere to the aircraft structures. The frequency of the microwave electromagnetic energy is such that it is strongly absorbed by the liquid water droplets but weakly absorbed by ambient air, frozen water or the aircraft structures, thus resulting in very efficient heating of the supercooled water droplets.