Inflight ice detection system

Abstract

A dual channel inflight ice detection system to detect ice accretion on an aircraft surface by illuminating an ice collecting surface mounted on an aircraft with linear polarized light. The backscattered light is acquired in two light conductors one with polarization sensitivity aligned to the transmitted light and the second with polarization sensitivity orthogonal to the first. The presence of ice is determined by the change in the ratio of light intensities in the two light conductors.

Description

FIELD OF THE INVENTION[0001]The present invention relates to inflight detection of ice accretion on the surface of an aircraft.BACKGROUND OF THE INVENTION[0002]Accretion of ice on the surface of aircraft is a problem experienced by flight operations. Such ice accretion may dramatically impact the performance characteristics of the aircraft and has been known as the root cause of a number of major accidents in recent times.[0003]Accretion of ice may occur when the aircraft is flying through supercooled liquid such as cloud, rain or drizzle and at a time when the temperature of the surface of the aircraft is below freezing point. The severity of the ice accretion is dependent on the supercooled water content, the temperature and the size of the cloud droplets or raindrops. Ice accretion on an aircraft surface increases drag, alters aircraft handling characteristics, disrupts the airflow, reduces lift and may result in a stall condition.[0004]Some large Transport and Regional Aircraft ...

AI Technical Summary

Benefits of technology

"The present invention is an improved system for detecting ice on the surface of an aircraft during flight. The system uses a special housing with an ice collecting surface and a light source to illuminate the surface. The light is then collected by two polarization sensitive light conductors and processed to determine the ratio of light intensity for each polarization state. This ratio indicates the presence of ice on the surface. The system is simple, reliable, and accurate in detecting low levels of ice accretion. It reduces pilot work load and provides timely and accurate detection of ice during critical phases in the flight. The components of the system exposed to the external environment are passive."

Problems solved by technology

Accretion of ice on the surface of aircraft is a problem experienced by flight operations.

Such ice accretion may dramatically impact the performance characteristics of the aircraft and has been known as the root cause of a number of major accidents in recent times.

Ice accretion on an aircraft surface increases drag, alters aircraft handling characteristics, disrupts the airflow, reduces lift and may result in a stall condition.

Such systems are expensive, consume considerable power and occupy significant space in the aircraft.

The pilot incurs a substantial distraction when required to make such observations.

Such an observation and related distraction may occur at a critical phase of the flight.

At the present time there are no known, reliable, un-attended and cost-effective inflight ice detection systems available for the complete range of aircraft from Transport Category to General Aviation type aircraft.

While such a system provides additional information the function of inflight icing detection does not provide a reliable detection of ice on the surface of aircraft because ice formation on the recessed surface of the probe lags ice formation on prominent aircraft surfaces.

Neither does the method provide an effective discrimination between water and ice.

Such a system requires significant set-up and is prone to changes from calibrated conditions.

Such a system is impractical for use inflight on the complete range of aircraft

Those experienced in the art favour the use of mono-static telescope arrangement due to difficulties in maintaining critical alignment between transmit and receive optics.

While such a system may provide information on the risk of icing conditions in volumes external to the aircraft it does not provide a reliable measure for detection of inflight ice accretion on the surface of an aircraft.

While such a system, containing a single light detector is compact it cannot discriminate contamination from ice.

As the refractive index of water and ice are very similar this and other advances using refraction techniques does not have the ability to effectively discriminate between ice and water.

The use inflight of such equipment for detection of ice on aircraft surfaces is not appropriate.

Unfortunately, such equipment cannot be used in an un-attended fashion inflight.

Unfortunately, such equipment is unable to detect inflight icing conditions in an un-attended fashion.

Unfortunately, such equipment is impractical for detection of inflight icing conditions in an un-attended fashion

While such equipment may be used inflight it's use is not accurate as in flight ice deposition can occur over a very wide range of temperature and flight conditions.

Unfortunately, in view of the randomness of ice crystal orientations, a variance will not be detected unless the sensors are set to detect at individual crystal level.

Such a system however is impracticable for use inflight on the complete range of aircraft

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