the implications of a remote detection system being
advise the pilot whether conditions are threatening to
onboard, for it implies that the aircraft cannot cope with
safe flight. Systems could provide air traffic controllers
icing (Bond et al. 1997).
(ATCs) and meteorologists with icing intensity
information and measured cloud microphysical
Cost is a large issue because aircraft that most need
remote ice-detection systems can afford it least--the
parameters. They could upload weather and satellite
regional airlines (Owen 1997). In addition, unless a
information from the surface and integrate it with
system is extremely inexpensive, remote-detection sys-
remote-sensor guidance (Bond et al. 1997). They could
tems will find little use on light, private aircraft
also use information from onboard in-situ sensors to
(Vigeant-Langlois and Hansman 1999). This is a signifi-
corroborate remotely sensed information and integrate
cant problem in the Far North where light aircraft oper-
all sources of information into a comprehensive icing
ate with no ice protection and with few or inadequate
advisory system. Overall, aircraft icing remote-sensing
systems could aid pilots, meteorologists, air traffic
weather advisories (Owen 1997). Even airlines operat-
ing large transport-category aircraft are reluctant to use
controllers, dispatchers, and ultimately the public
avionics they perceive to be of limited value because,
through improved aviation safety.
beyond the initial cost, there is the cost of flying it (lost
3.5.2 Regulatory issues
payload) as well as maintenance and training costs.
Regulatory agencies are responsible for providing
Weight and space are serious problems, especially
leadership and procedures for maintaining, improving,
for light aircraft and on many smaller civilian and mili-
and enforcing aviation safety. As a result, other than
tary helicopters. Although these aircraft may not be ice-
requirements of individual operators and the military,
protected, they may be IFR-rated and thus require the
systems for remotely detecting icing may not be used
additional security provided by remote ice detection.
on most aircraft without being required by regulators.
Single-engine light aircraft have little space and weight
Regulatory needs for operating in icing environments
reserves and, in addition, there are few locations for
have been identified by Brayton and Hakala (1996).
sensor arrays since the engine and propeller dominate
Nearly all changes in the regulatory environment that
the front of the fuselage. It may be possible, however,
they recommend would be affected by implementation
to operate a sensor through the propeller by synchron-
of remote ice-detection systems, and all would need
izing it with the rotating propeller (Kirkpatrick 1970).
evaluation should onboard remote-sensing systems
Power is also a problem on many aircraft. Larger
become available. The areas most affected, and requir-
civilian aircraft and military aircraft carry power-
ing greatest study by regulators, would be weather
demanding avionics and weapons systems. As a result,
reporting procedures between aircraft and the ground;
if space, weight, or power requirements are large for a
automated substitution for standard icing pilot reports;
remote-sensing system, tradeoffs between other avion-
handling procedures for aircraft wishing diversion;
ics or a weapons system and the remote-sensing system
flight crew, dispatch, and air traffic control (ATC) train-
must be considered. The icing remote-sensing system
ing; and icing severity terminology. Aircraft certifica-
may be avoided because of the small percentage of time
tion to fly in icing conditions probably would not be an
that it may actually be used. Military users may also be
issue, because specific aircraft capabilities within icing
concerned about the signature provided by systems util-
would not be affected by warning systems; only their
izing active rather than passive remote sensors.
ability to avoid and escape would be changed.
A remote-sensing system designed to detect icing
conditions ahead of an aircraft must be inexpensive,
3.5.3 Incentives
small in size, low in weight, and require little power.
Regulators determine what kinds of equipment
Though different types of aircraft may use systems of
should be mandatory on aircraft in different categories
different capabilities to reduce the impact of some of
of operation. Because of cost and complexity, unless
these factors, all development should focus on mini-
there are special needs of individual operators, regu-
mizing these liabilities.
lators may have to mandate installation of remote-
sensing equipment for detecting icing conditions on
3.5 Regulatory issues, weather forecasting,
specific classes of aircraft. Such a mandate would be
and traffic management
preceded by a thorough evaluation of remote-sensing
system capabilities, with a focus on their ability to
3.5.1 Functional requirements
enhance safety. Mandates for use on aircraft, or simply
Above all, a system designed to detect icing conditions
certification for those operators voluntarily using sys-
remotely is a pilot decision-support system (Clark
tems, would require that regulators consider issues of
1997). It is a system that senses conditions ahead of an
system integration and protocol compatibility.
aircraft and translates it into an icing intensity index to
9
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