Technology Database  Technologies of maintenance safety NEW METHODS OF COMPUTING ICING SHAPES AND THEIR EFFECT ON THE FLIGHT SAFETY OF CIVIL AIRCRAFT
New
Methods of Computing Icing Shapes And Their Effect On The Flight Safety Of Civil
Aircraft
A set of methods has been
developed for evaluating the effect of icing on flight safety at any stage of
aircraft designing.
The set of methods uses certain
information about the aircraft being designed to evaluate the adequacy of the
steps taken to assure flight safety in the icing conditions.
The methods developed make it possible to:
-
compute the shape and
dimensions of the ice formed on straight and swept wings depending upon the
profile contour and external flight conditions, and
-
justify the need to
consider changes of the heat emission factor with changes of the ice shape
and dimensions.
The necessary relationships have
been established for developing more accurate methods of computing ice shapes. A
substantial step forward in solving this problem has been the grouping of ice of
various shapes and dimensions according to its effect on aircraft aerodynamics.
Such a classification has made it possible to determine the precision with which
it is necessary to evaluate the shape and dimensions of ice, and define the
aerodynamic characteristics of the aircraft in flights of differing modes in
icing conditions.
In the absence of exact
mathematical models for computing stalling phenomena on the aerofoils in the
event of icing, the extensive experimental findings have been used to devise
methods of computing the effect of various shapes of ice on the aerodynamics of
the entire aircraft.
 The computed aerodynamic
characteristics have served to assess the speed values governed by FAR-25 or
FAR-23 and the characteristics of stability, handling, and flight envelopes. At
the final stage, we evaluated the flight safety level of the aircraft for
different icing conditions and formulated conclusions about their sufficiency
and about necessary additional work.
The proposed combined methods
substantially reduce the amount of necessary experimental wind tunnel and flight
testing to determine ice shape and dimensions, and their effect on the
aerodynamic characteristics, stability, and handling of the aircraft in icing
conditions when it is certified, which means a financial saving.
At present there are a number
of engineering and experimental methodologies in three main areas:
- determining ice shape and dimensions;
- determining aerodynamic characteristics
of aircraft in icing conditions, and
- computing the values of regimented
speeds, characteristics of stability and handling, and a general assessment
of flight safety.
In the immediate future work will
be completed on:
- a method of determining ice shape and
dimensions on swept wings, and
- a method of computing the aerodynamic
characteristics of aircraft with swept wings in icing conditions.
It is planned to work out a
method of evaluating the effect of a turboprop power unit on the aerodynamic
characteristics of an aircraft with unswept wings in the icing conditions and a
software interface for software products that support specific computation
methods.
Computation and evaluation of:
- aerodynamic FM characteristics in the
conditions of aerofoil icing;
- performance characteristics, and
- aircraft stability and handling in icing
conditions.
Recommendations:
- for selecting the type of anti-icing
system (AIS), its parameters, and its installation on the aerofoils of the
FM;
- on the automation of the control system
and flight envelope;
- on assuring flight safety in the event
of AIS failure, and
- on a program of control flights.
The effect of an AIS:
- Energy consumption
- Capital expenditure
- Operating expenses
- The development of an electronic system for
training aircrews to fly in icing conditions.
- The development of construction principles.
- Worsening of aerodynamic characteristics
- Reduction of flight safety (in the event of
AIS failure)
Source: SciTecLibrary.ru
Publishing date: October 19, 2000
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