Abstract: An optical device on board an aircraft for detecting icing conditions including an optical beam emitter to create at least one illuminated external volume of measurement through which there circulates a flow of air charged with water particles; a collector optical system for the collection of at least a part of the light beam back-scattered by the water particles (the external volume of measurement being located on the optical axis of said collector optical system); a photodetector for detecting back-scattered optical beams; a signal processor for processing the signal delivered by the photodetector to compute the severity of the icing conditions; an information provider for providing information on the calculated severity of the icing conditions. Advantageously, the optical means for the differentiation of device includes a differentiation for differentiating between liquid water particles and solid water particles, based on analysis of the polarization.

Abstract: According to the invention, there is provided an icing detector for detecting presence of both rime ice and clear ice in air comprising an ice collecting surface facing an oncoming air stream; light emitting apparatus for emitting a light beam crossing the ice collecting surface, having a prismatic light refracting window for refracting the light beam in a first direction, when no ice is present on the ice collecting surface; light sensing apparatus in a path of the second direction, and annunciating apparatus coupled to the light sensing apparatus for annunciating presence of ice when light is sensed by the light sensing apparatus.

Abstract: In a method of detecting ice on surfaces of an aircraft, a surface of an aircraft is scanned with laser light operating at different wavelength regions in a manner whereby the surface scatters the laser light. Laser light scattered from the surface is detected. Radiation outside the wavelength bands of interest is removed prior to detection. The detected, filtered, scattered laser light is processed to reconstruct images of the surface, thereby indicating areas of ice and water on the surface. The processing takes into account the directions of scanned continuous wattage laser beams relative to the surface, laser beam geometry factors due to changing distance between the laser beams and the surface while scanning, relative signal levels, normalizations and returns from other detectors. The material of the windows of the aircraft blocks the laser beam and any stray laser light. Also, the windows of the aircraft could be treated to block the laser beam and the laser light.

Abstract: A device for de-icing an external wall of a vehicle, of the type including a flexible covering (8) capable of at least partially covering the wall, and a compressor (9) whose delivery orifice (9B) is connected to the flexible covering in order to inflate it, via a control component (10). Advantageously, the intake orifice (9A) of the compressor (9) is connected to the flexible covering (8) via a controllable connection (11) which allows depressurization of the flexible covering and, when the pressure reduction reaches a predetermined value, feeds outside air to the compressor.

Abstract: An apparatus for detecting ice forming conditions includes a substrate having a first surface and a second surface; a sensor disposed on the first surface, the sensor being made of a material having a characteristic which varies in a known manner with respect to temperature; and a unit for monitoring the characteristic and for detecting ice forming conditions from the characteristic. A method for positioning the apparatus to detect ice forming conditions, to detect the presence of ice, and to determine an ice accretion rate is also provided.

Abstract: The invention is to a system and method for detecting materials on a conductive surface and measuring the thickness and permittvity of the material. A polarized Radio Frequency signal is reflected from a conduction surface having a material thereon. The reflected de-polarized signal is then processed to determine the thickness and permittivity of the material on the conductive surface.

Abstract: An icing sensor utilizes a surface gap transmission line along which a radio frequency is transmitted. The phase delay of the radio frequency along the transmission line is dependent upon the dielectric constant presented at the surface in the gap between the transmission line electrodes. Accordingly, changes of dielectric constant affect phase delay of the transmitted frequency. This phase delay may be used to detect the difference between ice, water and snow as well as the presence of freezing point depressing fluids such as ethylene glycol. When the sensor is mounted on an aircraft control surface, the presence and likelihood of icing conditions may be predicted. Through the use of one or more temperature, freezing point depressing fluids/water mixture determined from dielectric constant, and rate of change of the dielectric constant, it is possible to predict the time delay until icing begins. Thus, the sensor of the present application may safely reduce the effort and expense in aircraft deicing.

Abstract: A system is provided for reducing ice mass on an aircraft engine. A compressor inlet temperature and pressure sensor measures total temperature and total pressure at the inlet to the engine compressor. An ice shield is provided, wherein a plurality of wedge portions has multiple protrusions for promoting ice formation in multiple locations. The ice shield is separable from the sensor with which it interfaces. The ice shield comprises straight angle wedge shapes and curved surfaces to separate and minimize ice accretion in desired locations. The mass of each resultant ice formation is reduced to a size that the compressor inlet blades can withstand without deformation.

Abstract: The thickness of a semi transparent layer, such as ice, is determined by supporting the layer atop or above a light transmissive window and directing multiple light beams through the light transmissive window and into the layer. The light transmissive window has a higher index of refraction than the layer or any intermediate layer directly above the semi-transparent layer. Light beams are directed at an angle to the surface that results in total internal reflection from the outer surface of the supported semi-transparent layer. The light reflected to the rear of the window at the same but opposite angle is monitored and correlates to the thickness of the monitored layer. The spatial distribution of reflected light along the longitudinal axis of the window changes in dependence upon the thickness of the supported layer. Quantitative indications of that thickness are displayed and should that thickness exceed a prescribed level an alarm may be generated.

Abstract: A sensor is provided for detecting the presence of dielectric media, e.g., ice. The sensor includes a plurality of microstrip resonators which are positioned for electromagnetic coupling with a microstrip transmission line. The resonators produce amplitude minima in a radio-frequency signal that is carried over the transmission line. The resonance of the resonators changes in response to the addition of a dielectric coating. Each resonator can be configured with a different resonant frequency which serves as a signature that identifies the respective resonator's position. The sensor has a thin aerodynamic profile, can conform to nonplanar surfaces and its installation requires no intrusion into an aircraft skin.

Abstract: An embodiment of the present invention is a roadway sensor for surface installation in a hole such that a thin ceramic contact sensor may be used to measure and cross-compare fundamental physical antenna parameters of the space immediately above a roadway or bridge surface. Measurements are combined by a microprocessor to discriminate between dry pavement, water (rain), snow and ice above the sensor head. Ambient surface temperature, water depth and ice/slush conditions are determined to estimate any hydroplaning hazard and ice/antifreeze/water mixtures. The sensor comprises an antenna that exhibits a resonant frequency and an input admittance including a real term; a Maxwell bridge coupled to the antenna for detecting the resonant frequency, input admittance and real term; and a frequency sweeping oscillator for driving the antenna at a plurality of frequencies proximate in frequency to the resonant frequency.

Abstract: Insect debris is removed from or prevented from adhering to insect impingement areas of an aircraft, particularly on an inlet cowl of an engine, by heating the area to 180.degree.-500.degree. C. An apparatus comprising a means to bring hot air from the aircraft engine to a plenum contiguous to the insect impingement area provides for the heating of the insect impingement areas to the required temperatures. The plenum can include at least one tube with a plurality of holes contained in a cavity within the inlet cowl. It can also include an envelope with a plurality of holes on its surface contained in a cavity within the inlet cowl.

Abstract: A method and apparatus for determining the severity of icing conditions for an aircraft in flight. A mobile probe projecting from a surface of the aircraft is heated to a predetermined range of temperatures, and the total power required for the heating is measured. The measured total power is divided into a basic power corresponding to the thermal exchange in dry air having the same flow parameters as those measured and a complimentary power corresponding to the evaporating of drops of water contained in the actual air. A parameter representative of the speed at which the thickness of ice increases at the surface of the aircraft is computed from the complementary power.

Abstract: An ice monitoring and detection system for determining the presence and thickness of ice on a surface is provided. The system includes an imaging device which includes at least one lens for providing image signals of the surface. The imaging device is operable in a predetermined portion of the electromagnetic spectrum. Image signals from the surface are polarized into discrete polarization changes responsive to the camera receiving image signals proportional to amplitude modulated signals generated by the presence of ice. A processor is provided for converting the modulated signals into discrete polarization changes and for obtaining the difference between the discrete polarization changes which is proportional to the amount of ice on the surface. An indication device provides an output corresponding to the difference between the discrete polarization changes. The difference is indicative of the presence and amount of ice on said surface.

Abstract: An ice detector and deicing fluid effectiveness monitoring system for an aircraft is disclosed. The ice detection portion is particularly suited for use in flight to notify the flight crew of an accumulation of ice on an aircraft lifting and control surfaces, or helicopter rotors, whereas the deicing fluid effectiveness monitoring portion is particularly suited for use on the ground to notify the flight crew of the possible loss of the effectiveness of the deicing fluid. The ice detection portion comprises a temperature sensor and a parallel arrangement of electrodes whose coefficient of coupling is indicative of the formation of the ice, as well as the thickness of the formed ice. The fluid effectiveness monitoring portion comprises a temperature sensor and an ionic-conduction cell array that measures the conductivity of the deicing fluid which is indicative of its concentration and, thus, its freezing point.

Abstract: An apparatus for detecting ice includes a heat flow sensor which senses the rate of flow of heat through a member. At the same time, the temperature differential across the member is determined. Based on the temperature differential, it is possible to calculate a theoretical heat flow rate based on the assumption that there is no ice on the member. If ice is present on the surface of the member, the actual heat flow rate will be significantly less than the calculated or theoretical heat flow rate. It is contemplated that the apparatus and method of this invention will be particularly useful in conjunction with the detecting of the presence of ice on a wing of an aircraft.

Abstract: To determine whether ice is present on an aircraft wing, the intensity of light in a band between 1.16 and 1.20 microns is determined as is the intensity in a band between 1.24 and 1.28 microns. The contrast, defined as the difference between the intensities over the sum of these intensities, is determined. Because of the peculiar characteristics of the reflectivity of ice, water, Type I de-icing fluid, and Type II anti-icing fluid, if the contrast is positive, it is an indication of ice on the wing whereas if it is negative it is an indication there is no ice present.

Abstract: A safety system for detecting ice on the external surfaces of aircraft that are awaiting take-off from airports is disclosed. Multiple optical sensors mounted flush with the craft skin emit coded radiation signals away from the craft's skin. If a layer of ice is present on a sensor, light is reflected back to a corresponding detector, generating an electrical signal. Reflection from water or antifreeze or from environmental or endogenous noise yield distorted signals that are rejected by the code-reading circuitry. Relevant signals are sent to the cockpit, where the location of the ice on the aircraft is displayed for the crew, as well as to the airport tower via standard communication link, and to the flight data recorder. The invention assures that ice is detected at all critical times while the craft proceeds from the terminal to when it is airborne. Visual and audible alarms inform the pilot if unacceptable conditions prevail.

Abstract: An embodiment of the present invention is an ice detection system that comprises a network of thin, flexible microstrip antennas distributed on an aircraft wing at critical points and multiplexed into a microcomputer. Each sensor antenna and associated electronics measures the unique electrical properties of compounds that accumulate on the wing surface over the sensor. The electronics include provisions for sensor fusion wherein thermocouple and acoustic data values are measured. A microcomputer processes the information and can discern the presence of ice, water frost, ethylene-glycol or slush. A program executing in the microcomputer can recognize each compound's characteristic signal and can calculate the compounds' thicknesses and can predict how quickly the substance is progressing toward icing conditions. A flight deck readout enables a pilot or ground crew to be informed as to whether deicing procedures are necessary and/or how soon deicing may be necessary.

Abstract: A detector indicating ice formation on the wing of an aircraft or any planear surface, based on a thread-like or a tape-like transducer, through which an ultrasonic signal is transmitted at one end. The attenuation of the signal having passed through the thread is measured with a receiver at the opposite end while the thread is simultaneously being heated such that ice that may surround it melts again, the attenuation thus resuming its initial level.

Abstract: The present invention is an improved ice sensor which is particularly effective in measuring and quantifying non-uniform, heterogeneous ice typically found on aircraft leading edges and top wing surfaces. In one embodiment, the ice sensor comprises a plurality of surface mounted capacitive sensors, each having a different electrode spacing. These sensors measure ice thickness by measuring the changes in capacitance of the flush electrode elements due to the presence of ice or water. Electronic guarding techniques are employed to minimize baseline and parasitic capacitances so as to decrease the noise level and thus increase the signal to noise ratio. Importantly, the use of guard electrodes for selective capacitive sensors also enables distributed capacitive measurements to be made over large or complex areas, independent of temperature or location, due to the capability of manipulating the electric field lines associated with the capacitive sensors.

Abstract: An apparatus for identifying and measuring in real time substances overlying a surface comprises a plurality of electrodes, a temperature sensor, an electrode control system connected to the plurality of electrodes for defining an electric field, an amplitude and phase measurement system connected to the plurality of electrodes and to the electrode control system for measuring a plurality of currents responsive to the electric field and converting the currents to a measurement set and computer for storing a map comprising a partition of a vector space of predetermined characteristics of substances into regions of profiles corresponding to the substances which could be overlying the surface. The computer correlates the measurement set with the map thereby identifying and quantifying the substances overlying the surface and generates an output signal corresponding to the identity and quantity of substances overlying the surface.

Abstract: A warning system for detecting pre-flight aircraft icing employs parameter sensing means located at a plurality of locations along an aircraft structure, each of said sensing means positioned to sense an outer skin temperature of the aircraft structure at each of said locations and producing signals indicative thereof. Signal averaging means average said signals produced by said sensing means to produce signals representative of the average value of the outer skin temperature in a predefined area. Relative humidity sensing means produce a signal representative of the ambient relative humidity surrounding the aircraft structure prior to takeoff. Comparing means compare the outputs of said averaging means and said humidity sensing means with predetermined values of same defining an icing susceptibility region and produce a signal when the value of the sensed parameters falls within said region.

Abstract: An aircraft icing detection system detects accumulation of ice on an upper surface (12) of a wing (10) of an aircraft. The system includes an air pump (18) that delivers air through first and second conduits (24, 26). The first conduit delivers air through a first air knife (32) to openings (34) in the upper surface of the wing. The second conduit delivers air through a lower wing surface (14) through openings in a second air knife (42). When ice accumulates on the upper surface, flow from the first air knife is restricted. A differential pressure sensor (46) senses a pressure difference between the conduits and warns the pilot of possible ice accumulation by illuminating a warning light (50).

Abstract: A detector system for detecting the formation of ice on an aircraft outer surface, e.g. wing skin. The ice detector system utilizes a light source, light detector and temperature sensor coupled together for providing signals representative of icing which may be utilized to provide an alarm to the cockpit of the aircraft. Built In Test Equipment (BITE) is also included in the detector system for system failure indication to the pilot of the aircraft.

Abstract: The de-icing system of the present invention comprises a piezoelectric sensor means and a processor means. A piezoelectric film is the preferred sensor means and a microprocessor is the preferred processor means. In a preferred embodiment, a strip of piezoelectric film placed at a point of model kinetic energy such as the boundary layer transition point or the vortex generator of the aircraft. Such placement of the strip provides adequate airflow to excite the piezoelectric film without using a power source, thus providing a passive system. The sensor allows measurement of distributedSTATEMENT REGARDING FEDERALLY SPONSORED RESEARCHThis invention was made with Government support under Contract No. DAAH01-87-C-0860 awarded by the Defense Advanced Research Agency (DoD), Defense Small Business Innovation Research Program. The Government has certain rights in this invention.

Abstract: The invention provides an apparatus and method for detecting the presence of ice on a surface. The invention uses cameras to allow ice detection over a large area instead of a single point. The detecting apparatus provides an improved deicing apparatus.

Abstract: A source sends light towards a receiver through an optical channel, a part of which has an interface with the external environment. The light that reaches this interface is reflected towards the receiver when the external environment is in contact with air and is refracted towards the external environment in the presence of water or ice. In streaming down the interface, the rain creates a modulation, not created by ice, in the signal of the receiver. The circuits downline of the receiver search for this modulation to determine whether the modifications of the signal of the receiver are due to rain or to ice.

Abstract: A system and method for detecting the state and thickness of water accumulation on a surface incorporates a plurality of spaced, thin, electrically resonant circuits bonded to the surface and a radio frequency transmitter for exciting the circuits to resonance. A receiver detects the resonant signal from each circuit, determines the resonant frequency and quality factor of the circuit and correlates that information with predetermined data representing changes in resonant frequency and quality factor as a function of liquid water and ice accretion to thereby establish the state and thickness of water overlaying the circuits.

Abstract: An ice detector probe senses an ice deposition from an air mass flowing relative to the probe. The probe includes a support for installation of the probe to receive the airflow and an element formed on a substrate having a sensing surface which directly receives the airflow. The element heats the sensing surface to melt an ice deposition formed thereon. The resistance element also senses the sensing surface temperature during heating and provides an output representative of such temperature.

Abstract: An ice detector circuit for sensing an ice deposition on a sensing surface of an ice detector probe from an air mass flowing relative to the probe. The probe includes a heater to heat the sensing surface and a temperature sensor for sensing the sensing surface temperature during heating. The temperature sensor provides the circuit with an output having a level varying as a function of the sensing surface temperature. The circuit includes a controller which selectively energizes the heater, a timer which provides a timing output representative of a time interval elapsed between selected temperature sensor output levels, and computing means, such as a microprocessor, which computes an output representative of ice deposition as a function of a predetermined relationship between ice deposition and the timing output.

Abstract: A matter sensing apparatus includes a piezoelectric transducer, having a face susceptible to matter accretions at a surface for which matter accretion detection is desired. The electrical circuit of the transducer is coupled in the feedback path of an amplifier to establish an oscillator that oscillates at frequencies determined by the resonant frequency of the transducer and the loading on its face. The oscillator signals are converted to binary signals and utilized with binary signals, provided by a thermostat, that a representative of temperatures above or below a selected temperature to provide signals indicative of whether ice or other matter has accredited on the surface.

Abstract: In a detection device of the presence of frost and/or measuring the thickness of the frost by ultrasound, a probe with a piezoelectric ultrasonic transducer generates an ultra-sonic acoustic emission wave and detects ultrasonic acoustic echo waves reflected by the frost. An actuating device for the probe is arranged to provide to the transducer electrical energizing signals. The probe comprises: a frost detector placed in front of the transducer and constituted of a material having an acoustic impedance between 30.times.10.sup.5 and 44.times.10.sup.5 kg m.sup.-2 s.sup.-1. This detector has a surface designed to be exposed to the surrounding atmosphere to be covered with frost. An acoustic delay device is adapted to ensure acoustic coupling and adaptation between the transducer and the detector and to separate in time the ultrasonic emission add reflected waves. A body of heat insulating material covers the assembly of the detector, the transducer and the acoustic delay device.

Abstract: Ice formation on an aircraft surface swept of an air flow is detected by using an electrical heater which produces a small limited amount of heat to, on the one hand a heat flow meter and, on the other hand to a heat sink. When there is no ice on the transducer it produces a large output signal but when ice forms on the transducer the ice, due to its high resistance to heat flow, causes a change in balance between the two heat flows and a change in output of the heat flow measuring transducer.

Abstract: Apparatus and method using internal reflection of electromagnetic radiation to detect ice or water on pavements or other surfaces and to continuously measure the thickness of the accumulation. A prism which is transparent to pulses of electromagnetic radiation from an emitter is mounted in the pavement with an exposed prism surface flush with, and in the plane of the surface being monitored for the accumulation. Radiation from an emitter is directed at the exposed prism surface at an angle so that the radiation is totally reflected when the exposed surface is bare, but only partially reflected when there is an accumulation. Radiation detectors are positioned so that changes in the intensity of internally-reflected radiation are measured and interpreted to detect the onset of an accumulation, measure the thickness of the accumulation, distinguish accumulations of ice from accumulations of water, and distinguish accumulations of mud or dirt from accumulations of ice or water.

Abstract: An anti-icing management system for a gas turbine engine according to which, at all times, only the required amount of heat is applied to inlet surfaces of the engine to prevent the formation of ice. Heated air is bled from the compressor discharge, or from some other suitable heat source, for this purpose. The amount of flow of the heated air is adjusted by an electronic control responsive to the temperature of the anti-iced engine inlet surfaces directly in the path of incoming air. The electronic control may be effective to admit flow of the heated air to the region to be heated when a separate ice detector determines the presence of ice and so informs the control.

Abstract: A thermal modulating control valve adapted for supplying thermal modulated bleed air for an aircraft anti-icing system comprises a valve body having an inlet adapted to be supplied with bleed air from a separate source and an anti-icing outlet for supplying thermal modulated bleed air for operating an aircraft anti-icing system. The thermal modulating valve is mounted in the body in communication with the inlet and outlet for supplying bleed air at a regulated flow rate which is reduced in response to increased temperature of the bleed air supplied to the valve. The thermal modulating valve includes at least one annular seating ring having a central bore and mounted on a support element, and the seating ring includes an annular ring sleeve spaced outwardly of the support element having at least one radial annular face concentrically mounted on the support element.

Abstract: An ice detector 11 is provided for the determination of the thickness of ice 22 on the outer surface 12 on an object (e.g., aircraft 10) independently of temperature or the composition of the ice 22. First capacitive gauge 16, second capacitive gauge 18, and temperature gauge 20 are embedded in embedding material 14 located within a hollowed out portion of outer surface 12. This embedding material 14 is flushed with outer surface 12 to prevent undesirable drag. First capacitive gauge 16, second capacitive gauge 18, and temperature gauge 20 are respectively connected to first capacitance measuring circuit 24, second capacitance measuring circuit 26, and temperature measuring circuit 28. The geometry of first and second capacitive gauges 16 and 18 is such that the ratio of the voltage outputs of first and second capacitance measuring circuits 24 and 26 is proportional to the thickness of ice 22, regardless of ice temperature or composition. This ratio is determined by offset and dividing circuit 29.

Abstract: To be able to determine an ice or snow formation reliably, a cold conductor connected to an electrical power source is provided, with which the heat abstraction intensely occurring due to ice or snow is measured and used as a signal for ice or snow formation. The intensified heat abstraction on the cold conductor is determined by a current meter for determining an increased power consumption or by a thermistor which is in heat-conductive connection with the cold conductor and switches the power supply of the cold conductor on and off as a function of the temperature.

Abstract: Apparatus for the prevention of the formation and the removal of previously formed ice from the surface of various articles. A piezoelectric material is applied to environmentally exposed surfaces which are meant to be kept ice free. An available power source is adapted so that whatever the source, it is converted into an alternating current. A microprocessor is provided that, in accordance with the type of material used, its thickness, its currie point, and any other parameters of the specific piezoelectric material necessary for consideration, that it receives a current of the proper amplitude, duration, wave length, and shape which will realize the amount of movement or deformation of the piezoelectric material necessary to prevent ice formation. Further, the piezoelectric material is applied in a grid formation which enables the microprocessor to magnify the deformation of the material and to receive feedback information from specific areas as to the temperature, pressure, density, size of raindrops, etc.

Abstract: An ice measurement instrument includes a waveguide operating in a transmission mode passing energy from an input port to an output port. The resonant frequency of the waveguide depends on the presence and/or thickness of ice at a measuring location. The energy applied to the input port is swept in frequency from a first frequency to a second frequency at or above an ice-free resonant frequency of said waveguide, and back to said first frequency. Energy received at the output port is peak detected to provide a detection signal with four recognizable transitions identifying a pair of peaks which correspond to the resonant frequency of the waveguide. The time delay between these peaks can be used, in comparison with the time delay corresponding to an ice-free condition, to determine ice thickness.

Abstract: A method of determining the temperature, preferably the ice boundary temperature, of an electrical resistive heating element of a de-icing system for airplanes, helicopters, and the like, preferably for a fully automatic control of the heating times of the heating elements. Additional temperature sensors are avoided and circuitry costs are substantially reduced by using the resistive heating elements themselves for determining the temperature. The resistance variation due to temperature variations of an element is ascertained by a current-voltage measurement, and a temperature variation of the element is determined from the resistance variation while using the temperature coefficient. The current-voltage measurement may be based on Ohm's law with a following analog or digital processing of the signal.

Abstract: An ice warning system comprising a diaphragm set into vibration at one of its frequencies of resonance by a piezoelectric cell. The diaphragm is coupled thermally to a metallic plate alternately cooled and heated respectively below and above the ambient temperature by Peltier elements connected to a reversible DC current generator. A microprocessor measures any variation of the resonance frequency caused by a deposit of ice on the diaphragm during the cooling or heating periods and delivers an alarm signal if this variation of frequency reaches and/or exceeds a predetermined value. The microprocessor controls the period, intensity and direction of the current delivered by the DC current generator as a function of the ambient temperature and the temperature of the diaphragm. The ice warning system is preferably utilized in the aeronautical field for indicating the likelihood of natural ice formation on the engines and the wings of aircraft.

Abstract: An improved ice detector has a vibrating element which has a front portion and vibrating means suitably disposed with respect to the vibrating element for exciting the vibrating element into vibration and means for sensing a shift of the frequency of vibration of the vibrating element resulting from a change of mass of the vibrating element due to ice accumulating thereon. The improvement is characterized in that the ice detector is supported with respect to a surface exposed to an air stream such that a cap on which ice forms and which is disposed on the front portion of the vibrating element, is exposed to the air stream and is formed to be substantially conformal to such surface.

Abstract: In a device for breaking up ice formed on a contoured surface before it reaches a dangerous thickness, a flexible and porous membrane is fixed on the contoured surface along airtight lines of contact defining elementary chambers, each of which communicates with a main chamber inside the contoured surface. The main chamber is fed continuously by a source of hot gases. The closing up of the pores of the membrane by ice causes an inflation of the elementary chambers and a deformation of the membrane. Application is to the cowl of the air intake of a turbojet engine and to a detector used for the control of a de-icing device of any type.

Abstract: A method and apparatus is provided for detection of the onset of a physical change in state of a flowing fluid medium or component of a flowing fluid medium, e.g. freezing, boiling, sublimation, crystallization. A surface in contact with the fluid medium is maintained at a temperature that is an approximately fixed amount below or above the general stream temperature of the fluid, by means of a thermo-electric heat pump, the temperature difference being sensed by thermo-couple means to obtain a control signal for regulating the output of an amplifier that drives the heat pump. Upon occurrence of the physical change in state to be detected, the amplifier output will fall or rise rapidly as the system tries to regulate the power input to the pump to keep the temperature difference constant and this swing is detected by a signal generator monitoring the output of the amplifier.

Abstract: Apparatus for indicating rate of ice accretion particularly for use in an aircraft, the apparatus including test surface on which ice forms in use. First and second gas conduits are supplied with gas from a common pressure regulator the inlet of which communicates with a gas supply. A control port of the regulator is supplied with a reference pressure signal and the regulator operates to maintain its outlet pressure at a predetermined amount in excess of the reference pressure. Each of the first and second conduits includes a restrictor and each conduit terminates at its end remote from the regulator in an orifice. The first orifice is adjacent the test surface and a pressure difference sensor is associated with the first and second conduits to produce a signal dependent on the pressure difference at points between the orifice and restrictor of the two conduits. The pressure difference signal is applied to an indicator.

Abstract: A system for detecting ice on exterior surfaces of aircraft by transmitting a relatively low power microwave electromagnetic signal into a dielectric layer functioning as a surface waveguide, and monitoring the signals transmitted into and reflected from the waveguide. The waveguide includes a termination element which is mismatched with the waveguide impedance, resulting in partial or total reflection of the microwave energy from the remote end of the waveguide. As ice builds up on the surface waveguide, the impedance or reflection characteristics of the composite waveguide comprising the ice layer and the permanent surface waveguide give a reliable indication of the presence and location of the ice. The reflection characteristics are conventionally monitored utilizing a dual directional coupler and a reflectometer.

Abstract: Apparatus for indicating the rate of ice accretion on a surface particularly for use in aircraft comprising a hollow housing divided internally by a resilient diaphragm into first and second chambers. A first conduit communicating at one end with a gas supply and terminating at its other end in a first orifice. Intermediate the ends of the first conduit is a first restrictor and the first chamber of the housing communicates with the first conduit intermediate the first orifice and the first restrictor. Movable relative to the first orifice is a test surface upon which ice can form in use. The test surface is in use moved at a known speed and at a constant spacing from the first orifice. A second conduit communicates at one end with the gas supply and at its other end terminates in a second orifice. Intermediate the ends of the second conduit is a second restrictor and the second restrictor is variable, the setting thereof being determined by the position of the diaphragm in the housing.

Abstract: Apparatus for indicating rate of ice accretion includes an endless test surface upon which ice forms in use. A gas flow passage terminates adjacent the surface in an aperture which is presented to and spaced by a known gap from the test surface. A flow of gas is generated in the passage towards the aperture and a drive arrangement drives the test surface past the aperture at a constant rate. An ice removal device is operable to remove ice from the test surface after the surface has moved past the aperture and there is provided a sensor which detects variations in the flow and/or pressure of the gas in the passage. These variations arise from the effect on gas flow of restriction of the gas by ice forming on the surface, and associated with the sensor is an instrument which provides an indication of the extent of the variation in flow and/or pressure and accordingly provides an indication of the rate at which ice is being accreted on the test surface.