In-flight icing occurs when aircraft impact supercooled liquid drops. The supercooled liquid freezes on contact
and the accreted ice changes a plane's aerodynamic characteristics, which can lead to dangerous loss of control. NASA's
Icing Remote Sensing System consists of a multi-channel radiometer, a laser ceilometer and a vertically-pointing Kaband
radar, whos fields are merged with internal software logic to arrive at a hazard classification for in-flight icing. The
radiometer is used to derive atmospheric temperature soundings and integrated liquid water and the ceilometer and radar
are used to define cloud boundaries. The integrated liquid is then distributed within the determined cloud boundaries and
layers to arrive at liquid water content profiles, which if present below freezing are categorized as icing hazards.
This work outlines how the derived liquid water content and measured Ka-band reflectivity factor profiles can
be used to derive a vertical profile of radar-estimated particle size. This is only possible because NASA's system arrives
at independent and non-correlated measures of liquid water and reflectivity factor for a given range volume. The size of
the drops significantly effect the drop collection efficiency and the location that icing accretion occurs on the craft's
superstructure and thus how a vehicle's performance is altered. Large drops, generally defined as over 50 μm in
diameter, tend to accrete behind the normal ice protected areas of the leading edge of the wing and other control surfaces.
The NASA Icing Remote Sensing System was operated near Montreal, Canada for the Alliance Icing Research
Study II in 2003 and near Cleveland, Ohio from 2006 onward. In this study, we present case studies to show how
NASA's Icing Remote Sensing System can detect and differentiate between no icing, small drop and large drop in-flight
icing hazards to aircraft. This new product provides crucial realtime hazard detection capabilities which improve
avaiation safety in the near-airport environment with cost-effective, existing instrumentation technologies.