Abstract: In accordance with at least one aspect of this disclosure, a method of detecting a fault in a plurality of optical detectors includes receiving a first return beam from a first optical detector interrogation beam to generate a first optical signal indicative of an atmospheric condition from a first location on board the aircraft and receiving a second return beam from a second optical detector interrogation beam to generate a second optical signal indicative of the atmospheric condition from a second location on board the aircraft. The method includes, comparing each of the first and second optical signals with a baseline value to determine whether there is a fault in at least one optical detector of the plurality of optical detectors.

Abstract: An electrothermal ice protection system (IPS) installed on an aircraft includes a sensor, a parting strip assembly, and a controller. The sensor monitors a direction of a local incident airflow that is imparted on the sensor. The parting strip assembly is coupled to the critical surface and includes a plurality of heating sections. The controller is in signal communication with the sensor and the parting strip assembly. The controller determines a direction of surface airflow incident on a critical surface of the aircraft based on the local incident airflow and selectively concentrates power to at least one targeted heating section among the plurality of heating sections with respect to non-targeted heating sections among the plurality of heating sections based on the direction of the surface airflow.

Abstract: An aerodynamic friction energy deicing system can include a heat energy device configured to be operatively connected to an aircraft structure and to convert heat energy due to aerodynamic friction on the aircraft structure into another form or to store heat energy due to aerodynamic friction on the aircraft structure. The converted or stored energy can be used for any suitable purpose, e.g., for use in ice prevention and/or deicing and/or powering one or more aircraft systems.

Abstract: A method of monitoring an ice protection system of a rotorcraft or an aircraft includes applying heat to rotating blades of the rotorcraft or the aircraft according to a heater duty cycle and determining an anticipated ice shed time for ice to shed from the rotating blades. Torque of the rotating blades is sensed, and an actual ice shed time for ice to shed from the rotating blades is determined based on the sensed torque. A status of the ice protection system is determined based on the anticipated ice shed time and the actual ice shed time, and the status of the ice protection system is output for consumption by a consuming system.

Abstract: An ice protection system for an aircraft includes an ice detector disposed in an external aircraft surface, a temperature sensor, and a controller. The ice detector includes an ice sensor. The controller includes an icing threshold module which receives a temperature measurement from the temperature sensor, receives an ice accretion signal from the ice sensor, compares the temperature measurement to an icing threshold temperature, and determines whether the temperature measurement is above the icing threshold temperature. The controller suppresses an icing conditions alert if the temperature measurement exceeds the icing threshold temperature.

Abstract: An electrothermal ice protection system (IPS) installed on an aircraft includes a sensor, a parting strip assembly, and a controller. The sensor monitors a direction of a local incident airflow that is imparted on the sensor. The parting strip assembly is coupled to the critical surface and includes a plurality of heating sections. The controller is in signal communication with the sensor and the parting strip assembly. The controller determines a direction of surface airflow incident on a critical surface of the aircraft based on the local incident airflow and selectively concentrates power to at least one targeted heating section among the plurality of heating sections with respect to non-targeted heating sections among the plurality of heating sections based on the direction of the surface airflow.

Abstract: A method of monitoring an ice protection system of a rotorcraft or an aircraft includes applying heat to rotating blades of the rotorcraft or the aircraft according to a heater duty cycle and determining an anticipated ice shed time for ice to shed from the rotating blades. Torque of the rotating blades is sensed, and an actual ice shed time for ice to shed from the rotating blades is determined based on the sensed torque. A status of the ice protection system is determined based on the anticipated ice shed time and the actual ice shed time, and the status of the ice protection system is output for consumption by a consuming system.

Abstract: A method including providing power to an aircraft probe anti-ice system, monitoring an actual power demand of the aircraft probe anti-ice system, monitoring an air data parameter and atmospheric conditions surrounding an aircraft and calculating an expected power demand of the aircraft probe anti-ice system based on the air data parameters and the atmospheric conditions, comparing the actual power demand of the aircraft probe anti-ice system to the expected power demand, and performing a corrective action if the actual power demand and the expected power demand are different by more than an acceptable amount.

Abstract: A method including providing power to an aircraft probe anti-ice system, monitoring an actual power demand of the aircraft probe anti-ice system, monitoring an air data parameter and atmospheric conditions surrounding an aircraft and calculating an expected power demand of the aircraft probe anti-ice system based on the air data parameters and the atmospheric conditions, comparing the actual power demand of the aircraft probe anti-ice system to the expected power demand, and performing a corrective action if the actual power demand and the expected power demand are different by more than an acceptable amount.

Abstract: An aerodynamic friction energy deicing system can include a heat energy device configured to be operatively connected to an aircraft structure and to convert heat energy due to aerodynamic friction on the aircraft structure into another form or to store heat energy due to aerodynamic friction on the aircraft structure. The converted or stored energy can be used for any suitable purpose, e.g., for use in ice prevention and/or deicing and/or powering one or more aircraft systems.

Abstract: Apparatus and associated methods relate to determining, based on a spatial extent of ice accretion, whether an atmosphere contains super-cooled water droplets that equal and/or exceed a predetermined size. A convex-shaped housing is mounted to an aircraft and exposed to an airstream. The convex-shaped housing has a testing region that is monitored for ice accretion by an ice detector. A boundary locator determines a specific location to be tested within the testing region. The determined specific location corresponds to a calculated boundary that separates an ice-accretion region from an ice-free region if the atmosphere contains super-cooled water droplets up to the predetermined size. If the ice detector detects ice accretion at the determined specific location, an alert is generated. The alert can advantageously inform a pilot of an atmosphere containing super-cooled water droplets that equal or exceed the predetermined size.

Abstract: Apparatus and associated methods relate to projecting a light beam onto an interior surface of an aircraft window so as to indicate a testing location to test for ice accretion. The testing location is determined, by a boundary locator, based on aircraft flight conditions, aircraft exterior shape, and a predetermined size of super-cooled droplets, which could present a hazard to the aircraft. The determined test location corresponds to a calculated boundary that separates locations where super-cooled water droplets of the predetermined size cause ice-accretion from locations where such particles do not cause ice accretion, for such aircraft flight conditions. The light beam is then projected onto the interior surface of the aircraft window at the determined test location. The projected beam of light can indicate, to an observer and/or a detector, a location to monitor for ice accretion caused by super-cooled water droplets of the predetermined size.

Abstract: Apparatus and associated methods relate to differentiating ice accretion caused by different supercooled water droplets on an airfoil of an aircraft. A sensor having a sensing surface region is mounted at a mounting location of the airfoil such that the sensing surface region is flush with a surrounding adjacent surface of the airfoil. Water particles of sizes less than or equal to a predetermined threshold do not impinge the sensor surface region at the mounting location when the aircraft is in flight. A sensor driver provides an excitation signal to the sensor. A signal detector detects a sensor signal responsive to the provided excitation signal. The sensor signal is indicative of water particles exceeding the predetermined threshold impinging the sensing surface region. In some embodiments, the sensing surface region is mechanically coupled to a resonant cavity. In other embodiments, the sensor is a surface resistance sensor configured to sense surface resistance.

Abstract: Apparatus and associated methods relate to determining, based on a spatial extent of ice accretion, a maximum size of super-cooled droplets contained in an atmosphere and/or if an atmosphere contains super-cooled water droplets that equal and/or exceed a predetermined size. A testing region on an exterior surface of an aircraft is monitored for ice accretion by an ice detector. A boundary calculator determines a specific location to be tested within the testing region. The determined specific location corresponds to a calculated boundary that separates an ice-accretion region from an ice-free region if the atmosphere contains super-cooled water droplets of no larger than the predetermined size. If the ice detector detects ice accretion at the determined specific location, an alert is generated. The alert can advantageously inform a pilot of the aircraft that the atmosphere contains super-cooled water droplets that equal or exceed the predetermined size.

Abstract: Apparatus and associated methods relate to projecting a light beam onto an interior surface of an aircraft window so as to indicate a testing location to test for ice accretion. The testing location is determined, by a boundary locator, based on aircraft flight conditions, aircraft exterior shape, and a predetermined size of super-cooled droplets, which could present a hazard to the aircraft. The determined test location corresponds to a calculated boundary that separates locations where super-cooled water droplets of the predetermined size cause ice-accretion from locations where such particles do not cause ice accretion, for such aircraft flight conditions. The light beam is then projected onto the interior surface of the aircraft window at the determined test location. The projected beam of light can indicate, to an observer and/or a detector, a location to monitor for ice accretion caused by super-cooled water droplets of the predetermined size.

Abstract: Apparatus and associated devices relate to a system for measuring a maximum size of super-cooled water droplets in a cloud atmosphere. The system includes a housing having a convex exterior surface on a forward end and having stabilizers projecting from an aft end. The system includes a gimballed mounting mechanism configured to attach the housing to an aircraft while permitting the housing to freely pitch and yaw with respect to the aircraft. When an airstream engages the stabilizers, the housing aligns with a direction of the engaging airstream. The system includes a sequence of indices on a corresponding sequence of ice-accretion regions of the convex exterior surface, each of the sequence of indices visible in the absence of ice accretion. The forward-most ice-free one of the sequence of indices is indicative of a maximum size of super-cooled water droplets.

Abstract: Apparatus and associated devices relate to a system for measuring a maximum size of super-cooled water droplets in a cloud atmosphere. The system includes a housing having a convex exterior surface on a forward end and having stabilizers projecting from an aft end. The system includes a gimballed mounting mechanism configured to attach the housing to an aircraft while permitting the housing to freely pitch and yaw with respect to the aircraft. When an airstream engages the stabilizers, the housing aligns with a direction of the engaging airstream. The system includes a sequence of indices on a corresponding sequence of ice-accretion regions of the convex exterior surface, each of the sequence of indices visible in the absence of ice accretion. The forward-most ice-free one of the sequence of indices is indicative of a maximum size of super-cooled water droplets.

Abstract: Apparatus and associated methods relate to determining, based on a spatial extent of ice accretion, whether an atmosphere contains super-cooled water droplets that equal and/or exceed a predetermined size. A convex-shaped housing is mounted to an aircraft and exposed to an airstream. The convex-shaped housing has a testing region that is monitored for ice accretion by an ice detector. A boundary locator determines a specific location to be tested within the testing region. The determined specific location corresponds to a calculated boundary that separates an ice-accretion region from an ice-free region if the atmosphere contains super-cooled water droplets up to the predetermined size. If the ice detector detects ice accretion at the determined specific location, an alert is generated. The alert can advantageously inform a pilot of an atmosphere containing super-cooled water droplets that equal or exceed the predetermined size.

Abstract: Apparatus and associated methods relate to determining, based on a spatial extent of ice accretion, a maximum size of super-cooled droplets contained in an atmosphere and/or if an atmosphere contains super-cooled water droplets that equal and/or exceed a predetermined size. A testing region on an exterior surface of an aircraft is monitored for ice accretion by an ice detector. A boundary calculator determines a specific location to be tested within the testing region. The determined specific location corresponds to a calculated boundary that separates an ice-accretion region from an ice-free region if the atmosphere contains super-cooled water droplets of no larger than the predetermined size. If the ice detector detects ice accretion at the determined specific location, an alert is generated. The alert can advantageously inform a pilot of the aircraft that the atmosphere contains super-cooled water droplets that equal or exceed the predetermined size.