In the future, several changes in flight activity could
early in the research and development process on scen-
affect vulnerability to icing:
ario and training aids, which may help establish the
direction of technology development.
Implementation of Free Flight may reduce air traf-
Although it may not be absolutely necessary, devel-
fic control surveillance of aircraft routes, making
opment of an icing avoidance avionics system also
pilots more responsible for weather avoidance.
requires an understanding of pilot decision-making pro-
Increased commuter aircraft activity will create
cesses. The form in which information is delivered to
more flights by smaller aircraft at lower altitudes
pilots may subconsciously affect their decision-making
and slower speeds, increasing vulnerability to
process (Hansman 1997). Understanding how pilots
icing.
make decisions for avoiding or coping with in-flight haz-
Increased military emphasis on helicopters and
ards will affect the development of a decision-support
UAVs, both uniquely vulnerable to icing, is
system. Appropriate paradigms for icing avoidance may
expected.
be current fielded thunderstorm and wind-shear avoid-
Increased air traffic is also expected globally, so
ance systems. Pilots generally view any information
to reduce the number of icing accidents the acci-
beyond that currently available in the cockpit as useful
dent rate must decrease (Brown and Dorr 1997).
(Erickson 1997), but the kind of information desired
2.5 Philosophy
must be identified: too much or inappropriate informa-
Icing remote-sensor development is driven essen-
tion could confuse pilots.
tially by one question: What icing information does the
The pilot's needs determine the information provided
pilot need to make better risk-management decisions?
by a remote-sensing system, but the atmospheric envi-
A remote-sensing system that reports icing potential
ronment and the physics of icing and aircraft flight deter-
ahead of an aircraft to a pilot is a decision-support sys-
mine what information must be sensed to create the
tem that provides information needed to make decisions
information the pilot needs. Pilots are concerned about
regarding flight safety. Pilots' needs drive the develop-
flight safety and are thus concerned about the perfor-
ment process because they are the ultimate users of
mance of the aircraft should it ice. Aircraft performance
information generated by the system. The development
changes in response to ice accretion on the airframe.
process, however, must work within the restrictions and
Weather is the phenomenon that causes changes in air-
opportunities provided by the aircraft, regulators, sens-
craft performance by providing conditions conducive to
ing technology, and meteorology.
ice formation on an airframe. Thus, the ice accretion pro-
Because pilot information needs are the primary dri-
cess may be viewed as an inputprocessresponse sys-
vers of the process, an early development requirement
tem (Fig. 1). Weather is processed by the aircraft to pro-
should be to determine what pilots need to know. Do
duce ice on the airframe, which, in turn, influences air-
pilot information needs change with platform, mission,
craft performance.
Weatheher
Weat r
Aircrafftt
Perforrfmrmce ce
Pe oan an
A
InpIut ut
np
Prrocess
P ocess
Resespoe se
R ponsn
Figure 1. Aircraft icing paradigm.
airspace class, mode of flight (i.e., approach, departure,
Sensing requirements are independent of specific air-
or cruise), or some other factor? Is a ground-based sys-
craft, because different aircraft process identical weather
tem sufficient, or would an aircraft-mounted sensing
conditions in different ways: The same weather condi-
system add significant value? What spatial and temporal
tions may produce different icing conditions on a light
resolutions are needed, and how do pilots prefer to view
piston-engine aircraft than on a jet transport or a helicop-
the data--as plan, profile, or perspective views, and as
ter. And identical weather conditions may produce dif-
individual temperature and liquid-water content maps,
ferent icing conditions on an aircraft in different flight
or as composite maps of icing potential? How should
configurations depending upon power application, angle
icing potential be expressed, and how should hazard
of attack, skin temperature, and other factors. Although
areas be identified? Though all of this information is
the meteorological conditions may be identical, the pro-
not needed to begin research in all areas, it does set the
cessed information provided by the remote-sensing sys-
stage and reduces the possibility of misdirecting
tem should be aircraft-specific to allow the pilot to antici-
research and development. It also allows work to begin
pate potential aircraft performance changes due to icing.
4
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